COMPENDIUM C O A S TA L M A N A G E M E N T P R A C T I C E S I N W E S T A F R I C A March 2022 1 © 2021 The World Bank 1818 H Street NW, Washington, DC 20433, USA. Telephone: 202-473-1000 Internet: www.worldbank.org This work was commissioned by The World Bank and prepared by the French National Research Institute for Sustainable Development (IRD) and the University of Cape Coast, Ghana (UCC) The findings, interpretations, and conclusions expressed in this work do not necessarily reflect the views of The World Bank, its Board of Executive Directors, or the governments they represent. The World Bank does not guarantee the accuracy of the data included in this work. The boundaries, colors, denominations, and other information shown on any map in this work do not imply any judgment on the part of The World Bank concerning the legal status of any territory or the endorsement or acceptance of such boundaries. Rights and Permissions: The material in this work is subject to copyright. Because The World Bank encourages dissemination of its knowledge, this work may be reproduced, in whole or in part, for non commercial purposes as long as full attribution to this work is given. Any queries on rights and licenses, including subsidiary rights, should be addressed to World Bank Publications, The World Bank Group, 1818 H Street NW, Washington, DC 20433; email: pubrights@worldbank.org. Cover photo: Benin. Photo: Corde ONG 2 COMPENDIUM C O A S TA L M A N A G E M E N T P R A C T I C E S I N W E S T A F R I C A Existing and potential solutions to control coastal erosion, prevent flooding and mitigate damage to society Bruna Alves Rodrigues, Donatus Bapentire Angnuureng, Rafael Almar, Aubrée Louarn, Pier Luigi Rossi, Laurent Corsini and Pierre Morand Prepared on behalf of the World Bank (WACA Program) by the French National Research Institute for Sustainable Development (IRD) and the University of Cape Coast (UCC) 3 4 ACRONYMS BCER Biographic Coastal Environment Requests CPT Coastal Planning and risk management Techniques EBM Ecosystem-Based Management EWS Early Warning Systems GDP Gross Domestic Product GFDRR Global Facility for Disaster Reduction and Recovery GIS Geographic Information Systems HES Hard Engineering Solutions Hs Wave heights ICZM Integrated Coastal Zonal Management IRD Institut de Recherche pour le Développement (the French National Research Institute for Sustainable Development) NDF Nordic Development Fund NbS Nature-based Solutions SES Soft Engineering Solutions TS Terms Searched UCC University of Cape Coast WACA West Africa Coastal Areas Management Program WoS Web of Science 5 Table of Contents Acronyms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Authors and contributors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Executive Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Box 1: Nature-based solutions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Theoretical framework of vulnerability Box 2:  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Illustration of Hazards and vulnerability in coastal social-ecological systems. . . . . . . . . . . . . . . . . . . 23 2. Geographical area of the Study. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 2.1. Geo-environmental characterisation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Meteo-Oceanographic drivers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 2.2.  Socioeconomic characterisation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 2.3.  Human-induced pressures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 2.4.  3. Coastal management practices and solutions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Hard engineering solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 3.1.  3.1.1. Breakwaters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 3.1.2. Groynes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 3.1.3. Jetties 3.1.4. Revetments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 3.1.5. Seawalls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.1.6. Dykes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Storm surge barrier/closure dam. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.1.7.  Land claim (or reclamation). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.1.8.  3.1.9. Cliff stabilisation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Illustration of Hard-engineering solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Soft engineering solutions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 3.2.  3.2.1. Beach nourishment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Dune construction/rehabilitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 3.2.2.  Wetlands and mangroves restoration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.2.3.  Fluvial sediment management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.2.4.  Coastal planning and risk management techniques. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.3.  Flood early warning systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.3.1.  Flood regulation through hydraulic structures operations. . . . . . . . . . . . . . . . . . . . . . . . . . . 52 3.3.2.  6 3.3.3. Groundwater management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Risk mapping, flood risk mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 3.3.4.  Illustration of Soft-engineering, coastal planning and risk management solutions. . . . . . . . . . . . . 55 3.3.5. Coastal setbacks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.3.6. Managed realignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 Flood proofing and sheltering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 3.3.7.  3.3.8. Coastal zoning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Map of examples of solutions implemented in West Africa coastal area . . . . . . . . . . . . . . . . . . . . 62 Floating agricultural management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 3.3.9.   on-intervention/do nothing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 3.3.10. N Conclusions for coastal management practices in West Africa . . . . . . . . . . . . . . . . . . . . . . . . . . 64 3.4.  4. Integrated coastal management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.1. The ICZM approach. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Ecosystem-based management: new principles for coastal zone management . . . . . . . . . . . . . 68 4.2.  The Volta Delta as a hotspot: a potential suitable case for EBM application in West Africa. . . . . 69 4.3.  Summary and recommendations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 5.  5.1. Key principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 5.1.1. Consider at least two spatial scales. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Define clear objectives in a participative way. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 5.1.2.  Build scenario for future by using single or several solutions. . . . . . . . . . . . . . . . . . . . . . . . . . 72 5.1.3.  Implement the plan sustainably and adaptively. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 5.1.4.  Collect data and maintain strong links with the scientific and educational networks . . . . . . . . 73 5.1.5.  Table summarizing solutions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 5.2.  REFERENCES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Appendix 1: Methodological approach: bibliometric and text mining analysis . . . . . . . . . . . . . . . . 86 1. Bibliometric. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 2. Text mining analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 7 AUTHORS AND CONTRIBUTORS The Compendium: Coastal Management Practices in West Africa was written by the Institut de AUTHORS AND CONTRIBUTORS Recherche et de Développement (IRD), in collaboration with University of Cape Coast (UCC). The team comprised Bruna Alves Rodrigues (Post-doctoral Fellow), Rafael Almar (Senior Research Fellow), Aubrée Louarn (Short Term Research Engineer), Pier Luigi Rossi (Senior Research Engineer), Laurent Corsini (Research Engineer) and Pierre Morand (Senior Research Fellow) supported by Nathalie Benarrosh (Research Engineer) from IRD and Donatus Bapentire Angnuureng (Research Fellow) from UCC. The report was prepared under the guidance of a World Bank team led by Maria Sarraf (Practice Manager) and Peter Kristensen (WACA Program Manager) with special thanks to Benoit Bosquet (Regional Director, World Bank). The team included Sarah Jung (Environmental Specialist), Kenichiro Tachi (Senior Environmental Specialist), Nicolas Desramaut (Senior Environmental Engineer), Arame Tall (Senior Climate Change Specialist), Sajid Anwar (Environmental Specialist), Madjiguene Seck (Senior Partnership Specialist), Orla Fagan (Editor) and Teddy Ruge (Designer). The report benefitted greatly from the useful comments and inputs provided by peer-reviewers: Alioune Kane (Professor, University Cheikh Anta Diop of Dakar), Issa Sakho (Associate Professor, University of Thiès), Ramesh Ramachandran (Director, India National Centre for Sustainable Coastal Management), Regina Folorunsho (Director, Marine Meteorology and Climate Department at the Nigerian Institute for Oceanography and Marine Research), Adoté Blim Blivi (Professor, University of Lomé), Denis Aheto (Director, University of Cape Coast), Yoshimitsu Tajima (Professor, University of Tokyo) and Denis Jordy (Program Leader, World Bank). The report was funded under the World Bank’s West Africa Coastal Areas Management Program (WACA) with the financial support of the Global Facility for Disaster Reduction and Recovery (GFDRR), the Nordic Development Fund (NDF) and IRD. 8 FOREWORD Erosion and flooding are the most visible consequences of coastal zone degradation in West Africa. Man- made and natural processes, aggravated by the effects of climate change, cause erosion and flooding. These threatened densely populated coasts, the nerve center of the region’s demographic and economic growth. Every year, coastal degradation takes a heavy toll on human life and socio-economic prosperity. Moreover, the Intergovernmental Panel on Climate Change (IPCC) projections suggest that coastal erosion and flooding in West Africa is set to increase in the 21st century. Understanding the hazards and managing the coastline sustainably is a major challenge for the development of the region. The West Africa Coastal Areas Management Program (WACA) supports ongoing efforts led by countries and regional institutions to strengthen the resilience of communities and ecosystems. This is achieved by providing financing, facilitating access to knowledge and deepening dialogue around development challenges. The main objective of the Compendium: Coastal Management Practices in West Africa is to make knowledge on coastal management practices available to practitioners and decision-makers engaged in building coastal resilience in West Africa. At the same time, it informs any stakeholder concerned by risks related to coastal erosion and flooding. It complements technical catalogs on vulnerability to erosion, flood risks and flood protection infrastructure in West Africa. The Compendium: - a  ssesses measures to address coastal erosion, prevent flooding and mitigate their impacts on society; -  provides a critical review of options for managing risks, based on an analysis of available scientific literature on coastal erosion and flood risks in West Africa; and - presents the principles, basic concepts, and decision-points to consider when planning and implementing  coastal management and gives specific options, classified under three categories: hard-engineering solutions; soft-engineering solutions and coastal planning; and risk management techniques. Those responsible for developing and implementing public policies would benefit from the chapters on Integrated Coastal Zone Management (ICZM) and recommendations. For practitioners, the chapter on solutions will provide ideas for actionable measures. In summary, the Compendium provides: -  etails of the geomorphological, meteorological, oceanographic, and social drivers of West African coastal d zones’ vulnerability to erosion and flooding; -  description and analysis of the advantages and disadvantages of various options. Already implemented solutions are reflected, and yet-to-be implemented solutions are discussed. This set of options will help practitioners decide on best options based on local conditions; - overview of how to implement an Integrated Coastal Zone Management approach; and - five key recommendations for good practice in coastal risk management along with a summary table of  management measures. These are expected to be useful to decisionmakers responsible for developing and implementing public policies for coastal risk management. Managing coastal risk and resilience requires a dynamic and adaptive response to evolving hazards. It must be grounded on economics, governance, legislation, and planning while considering social dimensions. All are not addressed in detail in this Compendium, but the social dimensions should be implicit in any solution. Coastal risk management projects must be conducted in an inclusive manner by integrating all stakeholders, especially the most vulnerable. In addition to the solutions presented in this Compendium, managed relocation of people is a potential adaptation option that needs practical tools and guidelines. Resettlement can be a terrible experience for those who must leave their homes and move to a new area, even if that area is nearby. It disrupts their normal way of life, can have an impact on the social fabric of a community, and can negatively affect livelihoods. The complexity and direct risk to livelihoods of such option, makes it even more important to carefully plan and establish good practices. The Compendium reflects the authors’ experiences and view, and do not necessarily reflect those of the World Bank, its Board of Executive Directors, or the governments they represent. 9 EXECUTIVE SUMMARY Senegal. Photo: Vincent Tremeau/World Bank Major obstacles to regional development In 2019, the average coastline retreat was estimated at -1.40m/year, -1.60m/year and -2.40m/year in Côte d’Ivoire, Senegal and Togo respectively. The result is an increase in population displacement and increasing material and economic loss. At the same time, the toll from flooding in major coastal West African cities regularly amounts to tens or even hundreds of deaths and missing persons, illustrated by the ‘Freetown disaster’, when floods of an exceptional magnitude led to the death and disappearance of 1,000 inhabitants of Sierra Leone’s capital in 2017. The unusually heavy and violent rains that fell on the region in September 2020 is a reminder that such disasters could become increasingly frequent in the future, significantly slowing down West Africa’s social and economic development. Coastal erosion and flooding negatively affects human well-being, economic activities, existing infrastructure and ecosystem services associated with fragile environments. Coastal erosion causes coastline retreat, lowers beaches, threatens homes, roads and activities, has a particular strong impact on agriculture, tourism and fisheries sectors and also increases the risk of flooding. The most frequent consequences of floods include water point pollution, the outbreak of opportunistic water- borne disease epidemics, mosquito invasions, destruction of infrastructure and cessation of activities. While not all floods cause human damage, the destruction of property causes long-term vulnerability and also affects livelihoods. Scientific publications show that all West African countries, from Mauritania to Nigeria, are affected by coastal erosion and/or flooding, at varying levels of severity. Some areas experience a more rapid coastal retreat or suffer more frequent and violent flooding than other areas. However, on a regional scale it is the entire West African coastline that should be considered at risk, as coastal areas concentrate the challenges for regional development. The population growth rate of major coastal West African cities is over 4 per cent, and home to a third of the region’s population. The West African coast is also home to large port complexes, strategic places for trade and commerce, and concentrates high productivity activities where more than half of the regional Gross Domestic Product (GDP) is produced. With climate change, West African coastal aeras will be all the more exposed to erosion and flooding in the coming decades, while projections confirm the concentration of the region’s demographic and economic growth on the coastal strip, in the immediate vicinity of the ocean, increasing coastal risks 10 Coastal area pressures of drainage systems are recognized factors which aggravate flooding. In general, planning policies failure set to increase in the face of urban population growth increases Coastal erosion and flooding are phenomena that coastal populations’ vulnerability to flooding. can occur naturally, independent of human activity. Acceleration in rising average sea levels, rainfall As a result, erosion and flood risks are classified as pattern disruption and aggravation in extreme weather ‘natural risks’ and the associated damages belong to and marine events are all consequences of climate the ‘natural disasters’ category. These designations change that tend to increase already existing introduce an important bias in the collective mind, threats. where erosion and flooding are often associated with natural causes, impacting society, but without It is in this context that forecasting models predict presenting a causal link between them. However, if increasingly strong population growth in coastal the meteorological, geological and oceanographic areas, due in part to current population numbers but characteristics of an area are obviously important in also to inland population migrating towards the coast. the process of erosion and flooding, scientific literature Many migrants are fleeing insecurity in countries shows that human activities and infrastructures experiencing conflict, as well as the consequences have a strong influence on these phenomena. of the great drought in the 1970s and 1980s. The prospect of greater employment opportunities and The geomorphological nature of West African coasts the lure of an urban and more modern way of life in remains a primary vulnerability factor for the region’s large coastal conurbations, provide strong attractive coastal areas. Mainly composed of loose sediments factors for migration. According to projections, the and highly mobile geomorphological formations (sandy rise in average sea levels will strongly affect West beaches, dune belts, coastal spits and mangrove Africa by 2060 because the region is home to low- estuaries), the West African coastline is by nature lying coastal areas where the highest population unstable and rapidly changing. The coastal areas’ low growth rate in the world is expected. and flat topography accentuates the risk of flooding. And the monsoon, which generates particularly violent The magnitude of current erosion and flooding and dangerous torrential rains in coastal areas, can events combined with extreme concentrations of cause major floods especially when combined with settlements and activities along the West African tidal and pressure effects. coast, increase the risks to dangerous levels and threaten the entire region’s development in the The shortage of sediment caused by dam long term. Risk management actors in West Africa construction is one of the main causes of are provided with a myriad of options for action to erosion in West Africa. As rivers are a primary fight coastal erosion and prevent flooding. source of sediment supply for the coastlines, dam construction on the main rivers considerably depletes the sedimentary balance of West African coasts, Status of management practices trapping sediments carried by rivers upstream from deployed in West Africa the deltas. Conversely, wave dynamics, swells and currents cause sediments to move along the coastline Heavy engineering, soft and nature-based solutions, in a west-east direction. The construction of large coastal risk prevention and management measures port complexes destabilized this sedimentary Management measures applied so far in West drift, causing sediment accumulations upstream Africa mostly rely on ‘heavy engineering’ measures and a deficit downstream. Certain defense works (or grey infrastructure), which involves erecting protecting against waves can also have the same structures to artificially stabilize the coastline. The effect. benefits of these measures make it possible to break Coastal ecosystems degradation aggravates wave energy, retain sediments and prevent flooding in the extent and severity of erosion and flooding low-lying areas. Groynes are the most used coastal events. Deforestation and wetlands loss due to defense structure in West Africa and mostly consist urbanization development and other activities of piles of rocks arranged perpendicular to the coast particularly agriculture, trigger erosion and flooding. to retain sediment upstream of the wall. Breakwaters, Indeed, mangroves retain sediment and slow down jetties, revetments, and dykes can also be seen from erosion processes, and wetlands serve as ‘buffer Senegal to Nigeria. While cliff stabilization methods zones’ reducing energy and flood volumes. could be used in some instances, for example at the tip of the Cape Verde Peninsula in Dakar, there Poorly controlled urban growth resulted in soil sealing is insufficient discussion for this option in available and an extension of urbanization in flood-prone literature. Additionally, scientific literature does not areas. A shortage or failure of rainwater drainage provide any examples of storm surge barrier use in and sewerage systems and solid waste’s obstruction West Africa. 11 Breakwater construction can be remarkably effective entire chain of sediment transport from the basin to and appropriate in instances when the risks are high. the coast. Currently, dams capture almost all sediment For example, Benin, Côte d’Ivoire, and Togo whose carried by rivers, however, scientific studies show the coasts are highly vulnerable to erosion, set up major primordial importance of river inputs which allow a breakwater construction projects to protect strategic natural replenishment of beaches and play a major areas such as the Abidjan port. However, building role in fighting coastal erosion. Recent engineering such structures comes with high costs and not within solutions allow the passage of sediments through reach of all territories while maintenance costs and the dams, but these solutions are costly. Integrated river technical skills required to maintain these structures sediment management aims to maintain sediment are grossly underestimated. It was the addition of balance over the entire watershed and conduct construction and maintenance costs that led, for impact studies for each river development project. example, to the abandonment of a serial groyne However, this requires advanced scientific expertise construction project near Cotonou in the early 2000s. and cooperation between institutions. Despite the Because these massive structures are expensive obstacles, this type of management should be and particularly visible on the landscape, they are considered, especially in large estuaries such as the perceived as a solid long-term solution. However, Senegal River where human and economic challenges evidence proves different and poorly maintained are high. revetments can collapse within just 15 years of use, as was the case in Jamestown, Ghana. The revetment In addition to engineering solutions deployed in in Jamestown was replaced with less resource- the field, disaster prevention and management intensive and technologically advanced gabion-based measures are options aimed at developing revetment consisting of steel cages filled with rock, knowledge around risks while applying practices which proved successful. Thus, the best management to mitigate the impacts of hazards on populations. option is not necessarily the most expensive, or the Early warning systems (EWS) and risk mapping are most high-tech, but the option that best takes into fundamental preventative measures in large coastal account the specificities of each risk context. It is cities, such as Dakar or Cotonou; and while flood prudent to recall these structures’ undesirable effects risk mapping is a relatively popular exercise in West in artificially stabilizing the coastline, disrupting the Africa, the entire regional territory is not covered. By natural movement of sediments with waves and identifying high-risk areas, it is possible to plan land currents while most of this type of infrastructure, use and avoid increasing the risks in vulnerable areas causes accretion upstream and leads to coastal – the aim of public policies for zoning coastal activities erosion downstream. and urban planning. Plans can define a minimum distance of constructions from the sea, as applied in Less environmentally intrusive engineering the tourist locality of Grand Bassam in Côte d’Ivoire. measures are also used to combat coastal erosion In more exposed areas, the relocation of people and and flooding in West Africa. These measures are goods is necessary. Relocation operations were mainly based on natural coastal structure restoration, carried out in Grand-Lahou and near Abidjan, Côte allowing the dissipation of wave energy, and providing d’Ivoire, while others are underway, for example in the a natural barrier to combat flooding, providing beach Guet N’Dar district in Saint-Louis, Senegal. However, nourishment, dune replenishment and restoration measures to organize the retreat of populations of wetlands such as mangroves and salt marshes. from the shoreline or to prohibit construction in Apart from mangrove reforestation sites, which are exposed areas require good technical knowledge, numerous in West Africa and particularly in Senegal, strong institutional capacity on the part of the public these solutions are still poorly developed in the authorities to enforce plans and the establishment of region. The Nouakchott dunes in Mauritania have dialogue with local communities. been successfully rehabilitated, but at a fairly high cost. The Gambia (Kololi beaches) and Nigeria Partly because of the difficulties related to the (Victoria Island,Lagos) opted for beach nourishment, implementation of soft engineering techniques and which also requires maintenance, as erosion the multisectoral nature of coastal planning, Hard processes continue and carry away new sediment. Engineering Solutions (HES), widely favored This management option can be combined with the by communities, were privileged over other construction of groynes to limit coastal erosion more prevention and risk management measures in sustainably. West Africa. While protective infrastructure can be highly effective, the excessive importance given to Finally, there are no cases in West Africa of integrated grey infrastructure caused a rethink because of the river sediment management at a watershed scale. The unaffordable high cost and collateral effects. There is aim is for a global vision of all the processes affecting now a preference for an appropriate combination of beach sediment balance, taking into consideration the hard and soft solutions according to the characteristics 12 of each site, to achieve sustainable measures with Implementing integrated less impact on the environment. management plan against Nature-based solutions coastal risks Nature-based solutions (NbS) have emerged as In order to determine the measures best suited to an innovative approach for sustainable coastal each local risk context and to ensure appropriate zone management. Best described as actions functioning, it is necessary to draw up a management relying on well-functioning ecosystems to address plan to define objectives, schedule the plan’s social challenges through services provided by nature, deployment and monitor results. NbS protect biodiversity while ensuring communities’ It is recommended to develop an integrated security and prosperity. More than a specific category management plan and avoid a risk management of management measures, NbS is a general plan independent of other territorial public principle of thinking and action where ecosystem policies. ICZM considers the coastline as a system services are fully integrated into coastal zone whose elements are interdependent and cannot be management planning. This principle of action fits modified without a knock-on effect elsewhere. ICZM particularly well with that of Integrated Coastal promotes a cross-cutting approach to coastal Zone Management (ICZM), since the application zone management, taking into account the interests of NbS requires a specific environmental and cultural of a multiplicity of stakeholders and considering the context focus, stakeholder consultation and equitable social, economic, and environmental challenges of the redistribution of ecosystem services over the long territory on an equal footing. ICZM also emphasizes term. Mangrove restoration is the main NbS method the importance of the land-sea continuum, insofar as applied in West Africa. land-based activities can have grave consequences In comparison to more cumbersome infrastructure on the marine environment and ocean dynamics measures, the advantages of NbS are evident with influence the occupation of the coastline, particularly fewer collateral effects and lower implementation in the context of strong coastal risks. Finally, ICZM and maintenance costs. NbS is not suitable for all relies on the anticipation of risks and the sustainability situations and may not be sufficient to limit risks, of its management approach, recommending that however it can be combined with more traditional different geographical and time scales are considered risk management options, such as dykes. While NbS and that a concerted approach is established appear to be a sustainable, gentle, and inexpensive between stakeholders. ICZM corresponds in a way way of managing risks, planning options should not to the application of the principles of sustainable succumb to a Manichean view of risk management by development in coastal areas. banning actions that do not comply with this principle. The integrated approach promoted by ICZM The main goal of a risk management plan remains the emphasizes the specificity of each territory and effectiveness of protective measures to ensure the the complexity of the processes that take place. safety of communities and limit damage, in the short, Nevertheless, the following main organizing principles medium, and long term. can be identified to take into account coastal risks in an integrated management plan. 13 1. Establish a territory diagnosis and 2. Propose several the risks estimate  - D  efine and bring together scenarios stakeholders. - dentify a combination of measures I to achieve the defined objectives. -  efine the study’s boundary, D The objectives defined in Phase 1 keeping in mind interweaving can be achieved, depending on the of geographical scales and means available to the community administrative levels. and the preferred stakeholder - C  ollect data on existing methods where it is often 4. Evaluate hazards and the probability necessary to put in place actions, 3. Deploy the integrated of occurrence in the near and that allow for complementary management management plan distant future. efficient risk management. plan in the field effectiveness - E  stablish several scenarios based - Strengthen - C  ollect monitoring data on - C  ollect data on the on these combinations; identify institutional a regular basis. demographic, economic, technical, financial and human capacity, if socio-political, environmental -  valuate objective E resources required to implement necessary and the territory’s achievements through morphological characteristics. chosen measures, plan deployment - Build defense indicators. It is also important to measure schedule, pre-existing constraints, infrastructure and disaster risk and preparedness benefits for the community, develop tools and - A  djust the actions as and response capacity limits negative impacts on the territory, public policies for necessary. of local authorities and civil and indicators to monitor and risk prevention - M  ake a complete periodic society. evaluate the objectives. Scenarios and disaster review of progress and must consider several time scales management. the action’s effectiveness, - B  ased on data analysis, to integrate changes in risk factors prioritize the area and human, and adapt the plan such as population growth, climate if necessary. economic or natural stakes change, etc. according to a vulnerability estimate focused on erosion -  dopt a main scenario. Scenarios A and flood risks. The aim is can be discussed upstream by to prioritize the areas for experts and then submitted to all protection. stakeholders. Various technical tools can be used to present the - D  efine, in a participatory scenarios: mapping, modeling, manner, management plan’s SWOT analysis, etc. objectives. Recommendations for good plan. This involves sharing the conclusions’ preliminary studies including territory diagnosis, define coastal risk management the management plan objective in a collaborative Good coastal risk management is considered to be a set manner and decide on varying management options of effective measures for the protection and development that can be applied (choice of final scenario). This of human, economic and natural assets in coastal zones. participatory approach should be continued during The measures should be decided and implemented in a concerted way between the territory’s actors and in line with the implementation phase, particularly to ensure the the objectives of existing territorial public policies. The use communities’ support for plans. of communities’ local knowledge, interdisciplinary scientific studies and technicians’ operational know-how promotes 3. A  dopt a flexible management plan where the acceptability, efficiency and sustainability of management objectives can be re-evaluated, and activities solutions envisaged. Finally, a global, systemic approach to adjusted according to risk environment the coastline is preferable, considering that coastal zones evolution. Some options could include a combination are interfaces between activities and terrestrial and marine of short-term effectiveness, for example, protecting environments, and are therefore complex places to be infrastructures with a dyke, with long-term analyzed at different scales. effectiveness, by relocating this infrastructure. With Aware of the pragmatic difficulties that such a theoretical demographic and economic change taking place approach raises, the authors identified four key points, in West Africa, it is recommended to provide for decisive in initiating good management of coastal risks: alternative solutions adapted to different levels of risk 1. C  onsider at least two geographic scales to when developing the management plan. It is essential analyze risks and implement measures. Risks to rely on projections established by scientists for this often originate as a result of global or regional purpose. dynamics and local factors of vulnerability. When 4. R  ely on data from observatories and scientific considering risk in a management plan, it is necessary programs to evaluate activities’ effectiveness, identify to take into account interweaving geographical possible environmental or sociological obstacles, and measures in hazard formation and risk construction, more broadly, monitor the coastline’s evolution. On as well as administrative capacity in development and a regional scale, an observation network should be implementation of territorial public policies. activated where data centralization and open data 2. I dentify all actors involved in risk management sharing is available, and the existing educational and offer opportunities for stakeholders to system should be strengthened in Masters, PhDs and participate in development of the management thematic workshops. 14 1. INTRODUCTION Ghana. Photo: Hen Mpoano The West Africa coastal area covers about 6,000 Km and is home to 14 countries from Mauritania to Nigeria, including the archipelagos of Cape Verde and São-Tomé-and-Príncipe. The extensive coastline is significantly exposed to erosion and flooding, previously identified as disaster risks and a major cause of coastal zone degradation. West Africa’s coastal area is home to one-third of the region’s population and encompasses more than half the region’s GDP. As the area accounts for most of the region's potential demographic and economic growth, protecting coastlines from risks of erosion and flooding is a major challenge for the 14 countries and indeed presents challenges for the entire region’s development. Investment is required along the coastline to ensure vulnerable areas are protected from coastal hazards. Risk reduction using physical, nature-based, policy or regulatory solutions is essential to reduce vulnerability in exposed areas with high population centres. Investment will protect economic activities and natural resources from a multitude of prevailing hazards. While many types of solutions were already deployed at multiple sites and locations on West African coasts, further actions will be required for deployment in future. To learn from past and existing experiences and to better guide future actions and policies for coastal risk reduction, it is necessary to take stock of levels of success already achieved, just as it is important to present what can be achieved into the future. This assessment is reviewed critically, referring to the criteria of ‘good practices for coastal management’, assuming that ‘good practices’ are those that meet the following criteria: •  upported by clear objectives which can be presented to and discussed with decision-makers, stakeholders S and communities. • Offers estimates for implementation costs and maintenance compared to the expected long-term benefits.  •  Following the previous point - presents a favourable cost-benefit balance in the long term. •  otential harmful collateral effects, from a socio-economic and environmental viewpoint are clearly identified P and listed. • Create opportunities to monitor and mitigate harmful collateral effects (if any).  15 This Compendium aims to introduce and update territory ordinance and management activities. coastal management practices, or adaptation responses which currently exist – whether or not Coastal protection measures are usually divided into applied to the West Africa scenario. In this report, two categories (UNDRR, 2017) - structural and non- coastal risk management practices are presented structural. Structural measures refer to construction according to the following: and engineering techniques physically deployed and used in the field to reduce coastal hazards 1. Hard engineering solutions. exposure. These measures are also used to increase 2. Soft engineering solutions. infrastructure’s resistance and resilience in an entire 3. C  oastal planning and risk management territory. Non-structural measures do not require techniques. physical intervention in the field but the increased knowledge of risks and developing practices are used Hard engineering solutions (HES) are utilized as to mitigate impact, such as urban planning and land- coastal management techniques to protect against use planning while raising awareness of coastal risks, erosion and flooding, while also absorbing wave research and data gathering. energy. These techniques are used to artificially stabilize the coast, preventing sea-land interactions This report separates structural measures into HES and subsequent sediment exchange. As highly visible and SES, with emphasis on SES as a less intrusive man-made structures, the techniques stop or disrupt option for the environment while inclusive of nature- natural processes but can result in detrimental effects based solutions (NbS), a new paradigm which recently on distant coastal environments in the same region. emerged in coastal zone management. NbS are HES structures are expensive to construct and in the actions that rely on well-functioning ecosystems to years that follow, appropriate maintenance is required address social challenges through nature's ecosystem to extend the structures’ lifespan. In most cases, services, protecting biodiversity while ensuring human HES structures are not permanent and after years or well-being. Separating structural measures into HES decades of effectiveness, they weaken or become and SES make it possible to better highlight the type so damaged they require new investment. However, of measures in line with the principles of NbS. In short, in some cases, HES solutions are necessary given NbS is not considered a distinct additional type of social and economic constraints. solution, but rather a selection of solutions recognised in other options such as SES and CPT, which respect Soft engineering solutions (SES) are frequently the eight NbS principles (see Box 1). As a result, NbS proposed as an eco-friendly option to work with will not be specifically described but solution types nature, protecting the coast rather than hindering compatible with NbS are mentioned in the second or interfering with natural processes. Whereas HES column of the summary table provided in chapter 5. exclusively involves structural features such as Finally, non-structural measures correspond to coastal seawalls and breakwaters (Pontee et al., 2016), SES planning and risk management techniques. is considered a paradigm shift in coastal protection and risk reduction. The influence of SES on coastal The challenge of this work is to present an approach processes improves service levels provided by that combines all these options, which can be applied sea defence/coastal protection structures. Using to the West African coast, regardless of the country, ecological principles and practises, SES results in less coastal community ethnicity, subsistence activities, impact on the natural environment, is cost effective type of coast (whether sandy beaches, mangrove to implement and maintain, and creates greater forests, estuaries or coastal lagoons), meteo-ocean long-term sustainability when compared to hard conditions and coastal hazards. This approach is engineering projects. classified under an integrated coastal management approach, based on the coast’s characteristics, the Coastal planning and risk management people who live in the areas, and designed accordingly. techniques (CPT) refers to planning for physical layout and land use, and an essential component of Suggestions put forward to improve coastal a community’s long-term resilience. It encompasses management are largely based on a methodology the constructed and natural environment by shaping covering an extensive literature review of scientific areas where development occurs and identifies areas and academic articles, and available reports from for open space or preservation. Key components trustworthy institutions and organisations, which best include comprehensive planning, zoning regulations describe the realities of West Africa coastal areas. and building codes where CPT is viewed as a tool for 16 Box 1: Nature-based solutions NbS are defined as actions to protect, engineering solutions), NbS is based on the sustainably manage, and restore natural conservation or restoration of ecosystem or modified ecosystems which adapt and services or is complementary to other address social challenges effectively, while actions, such as a mix of seawalls and simultaneously providing human well-being mangroves protecting a coastline from and biodiversity benefits (Fischborn and Herr, ocean surge. This principle requires policy 2015). NbS are not a particular type of solution but coherence (Cohen-Shacham et al., 2019) and an overarching concept which can encompass is linked to Principle n° 8 described below. different types of solutions, such as those in the  etermined by site-specific natural and 3. D SES and CPT groups, so long as the design and cultural contexts including traditional, local its implementation comply with the following eight and scientific knowledge. principles:  roduce societal benefits in a fair and 4. P  mbrace nature conservation norms and 1. E equitable way, in a manner which promotes principles. While NbS remains an important transparency and broad participation. global priority in its own right (Cohen- Shacham et al., 2019), it should not be  aintain biological and cultural diversity and 5. M seen as an alternative to, or a substitute the ability of ecosystems to evolve over time. for nature conservation, but as an option Applied on a landscape scale. 6.  where solutions can complement and benefit  ecognise and address trade-offs between 7. R from nature conservation efforts across a immediate economic development benefits landscape. For example when a protected and a full range of ecosystems services in the area was established to conserve certain future. species, but later contributes to an NbS intervention (Cohen-Shacham et al., 2016).  onstitute an integral part of the overall policy 8. C design and measures or actions to address mplemented alone or in an integrated 2. I a specific challenge such as large-scale manner with other solutions to social interventions. challenges (for example technological and This report’s first methodological step entailed a The main body of this report is based on a thorough bibliometric analysis based on keywords and meta- analysis of scientific articles and reports, part of the information conducted in scientific articles published authors' large references library. References were also in academic journals (Web of Science), at global and researched during the bibliometric analysis and other regional levels. The aim of this first stage research relevant reports and works of interest were used in the was to investigate whether the scientific community compendium. in West Africa has embraced coastal management and defence against erosion, identify research actors, Chapter 2 looked at the Study Area and presented the prioritise research topics and ascertain which topics geomorphological and demographic characteristics are considered irrelevant for the research. of West African coastal areas, which provided analysis and examined the role of waves and drifts in erosion One of the key conclusions of this literature review is the and flooding processes. This chapter explores the 10-year gap that occurred between the development natural mobility of coastal formations, elements of of coastal erosion and flooding research on a global anthropic origin that disturb geomorphological and scale and at the West African regional scale. While biological systems, and their role in aggravating research was embraced worldwide in the 1990s, erosion and flooding processes. An assessment of studies specifically on coastal erosion and flood risk areas and communities highly exposed to erosion and management in West Africa began in earnest in 2005. flood risks helps in understanding the principal factors However, the number of scientific publications related of fragility in these territories. to coastal environment is now increasing relatively faster at a regional scale, evidence of the importance Chapter 3 examines Coastal management practices that is now given by the scientific community in West and solutions, critically presenting existing options Africa. The literature review is available in Appendix 1. for managing erosion and flood risks in line with 17 the typology developed through HES, SES and Based on ICZM methodological approaches CPT. Chapter 3 sets out each solution in a generic developed in the previous chapter the final chapter manner and then deliberates the pros and cons of this report addresses decision-makers by providing including cost, before highlighting the potential key element options to choose coastal management collateral consequences which need to be reflected practices best suited to each local issue. by decision-makers and managers. Examples of its application in West Africa are also outlined, along The information in this report should help decision with success and failure examples. Solutions used makers prioritise plans based on identified hazards elsewhere in the world are examined for comparison and choose management options for selected to ascertain whether specific solutions are unsuitable West African coastal areas, future interventions and to West Africa coasts’ physical conditions or solutions investment plans at national and regional level. This were not fully implemented due to insufficient financial compendium is organised to bridge research and resources. practices in an easy-to-read language, accessible to decision-makers and practitioners. A glossary of Solutions should be deployed ideally within a coastal vulnerability terms is presented in Box 2, providing a zone management plan complying with the principles common basis of definitions for this report. of Integrated Coastal Zone Management (ICZM) - a theoretical concept for coastal zone management, We recognise that this work provides baseline corresponding to the sustainable development information and analysis. Proposals for investment guideline in coastal areas. would require further studies, to develop, design and ensure efficiency based on local situations, for From this theoretical approach a number of practical example hotspots in the area of interest within West rules for sustainable coastal zone management are Africa coastal areas. derived, which are presented in Chapter 4, Integrated Coastal Management. This chapter highlights ecosystem-based management as a coastal management practice to complement ICZM and explores the restoration of ecosystems in a territorial development project. Figure 1 - West Africa, Gulf of Guinea and the countries covered by this study 18 Senegal. Photo: Vincent Tremeau/World Bank 19  heoretical framework Box 2: T of vulnerability 1. Vulnerability: general definition •  hort-term impulses and shocks, whether S natural or human-induced are individual Vulnerability was traditionally etymologically defined distinct actions or ‘events’ which cause a as the susceptibility of a system or object to be temporary or permanent change in the existing damaged when exposed to a hazard or threat, state of the ecological/human system by regardless of its origin (D'Ercole et al., 1994; Eakin disrupting its structure and functions. Natural and Luers, 2006; Meur-Férec et al., 2008; Turner et events include wildfires, hurricanes, floods, al., 2003). abnormal seasonal drought peaks etc. Man- The object or system considered can be an made events can include new infrastructure individual, a community, a society, an ecosystem construction (on a given place) or an oil spill or, more appropriately in this context, a ‘social- as a result of pipeline vandalism or an accident ecological system’. The system can be defined caused by a ship. (Berkes and Folke, 1998; Gallopin, 2006) as the In addition to variation between pressure and pulse, combination of a social (human) system and an the hazard analysis also attempts to identify root ecological (biophysical) system of a given territory. causes at the origin of an onset. The root causes are This takes into account interactions that links and generally referred to as ‘driving forces’ or ‘drivers’, places systems in a search for sustainability. Such which can be classed as natural (such as the natural system view is particularly relevant when addressing climate cycles) or those that directly involve human coastal vulnerability issues in a comprehensive and activities, which are referred as ‘anthropogenic’ inclusive manner. drivers. The latter can be local, for instance, the While there is general agreement on the basic population growth of a region; or at a more macro definition of vulnerability in the available literature, a level - international economic exchange fluctuations. wide variety of approaches on this concept emerged It should be noted that while global warming is a across disciplines. Some relevant contributions to driver that appears as a natural-looking climatic the practical analysis of vulnerability in the context phenomenon, it’s proven to be mostly the result of of coastal environment, are outlined below. human activities. Improving knowledge of hazards’ original causes 2. Coastal hazards can allow for greater anticipation and help reduce Investigating a system’s vulnerability necessarily the system’s vulnerability (Turner et al., 2003; involves looking at two objects, the hazard (or threat) Meur-Férec et al., 2008). In order to choose the likely to cause damage and, the system itself, which best risk management options, it is essential to is likely to suffer damage. The type of events which have a thorough understanding of coastal hazards’ generate hazards and threats, and may endanger dynamics and the system which can be damaged. coastal ecosystems or social-ecological systems Choosing the best options involves gathering data can be considered as (Turner et al., 2003; Collins and developing research on hazard drivers but also et al. 2011): on the exposed system’s characteristics whether social, economic, or ecological. •  ong-term pressures, such as rising sea levels, L eutrophication or rising average temperatures which are sustained and chronic. Some 3. The risk approach pressures are closely linked to human influence The notion of risk appears at the intersection of such as fuelwood harvesting, sand extraction, hazards and stakes (Meur-Férec et al., 2008). Risk coastal groundwater salinization and land-use is defined as the probability of a hazard occurrence change. In most cases, there is a growing weighted by the magnitude of its potential impacts pressure trend. (Turner et al., 2003). The likelihood of system 20 damage raises the question of what aspect of Vulnerability analysis according to these three key protection should be prioritized in the event of a concepts sets out a chronological mapping (a type hazard. This is a difficult exercise which can be a of sequencing) of events and processes affecting source of tension in coastal areas, as stakeholders the system. If the system is exposed, then its don’t necessarily have the same vision of priorities sensitivity is challenged by hazards. If its resistance in terms of protection, but where prioritization is and absorption capacity does not allow it to remain essential for effective risk management. in good functioning condition, then the system is significantly impacted. If the system is impacted, The concept of risk is therefore related to the then it must demonstrate its adaptive capacity semantic field of vulnerability but is not synonymous to recover functionality in a satisfactory manner. with it. A vulnerability analysis based on risk analysis However, it should be noted that this post-impact alone is therefore incomplete (Frazier et al., 2014). functionality may change to the period before the shock-event. Exposure, sensitivity and adaptive 4.  capacity 5. Resilience Research identified three other key concepts in Parallel to the vulnerability paradigm, a new vulnerability analysis (Frazier et al., 2014; Turner resilience paradigm emerged in the 1970’s and et al., 2003): exposure, sensitivity and adaptive quickly gained significance. This term, inherited capacity. from physical and then ecological science, initially •  xposure mainly takes a spatial dimension; E referred to the capacity of a system to regenerate however, the question is whether the hazardous after a violent shock capable of almost completely phenomenon has sufficient force to reach the destroying communities and infrastructure. system, and how often it may occur. Resilience is therefore defined as the capacity of • S ensitivity is the immediate impact degree the system to return to effective functioning after that the system will experience if the a disaster and as such, the notion of resilience is phenomenon occurs. It depends on two closely related to adaptive capacity. system characteristics - resistance and absorption capacity. Resistance is defined However, the word ‘resilience’ is also used in as the system’s ability to strictly maintain its a much broader sense to refer to all the ways in structure and functionality, allowing a system which a system manages to cope with danger, to be immutable during a crisis. The absorption encompassing resistance and adaptive capacity. capacity refers to the system’s ability to provide This can be defined as a system’s ‘defence’, which - ‘softness’ or flexibility. Absorption capacity is is exposed to a threat - a definition adopted by the degree of variation a system can undergo the Intergovernmental Panel on Climate Change. while continuing to operate normally and its The term resilience then almost mirrors the ability to quicky return to its original state. The term vulnerability, the former seen as a positive system’s resistance and absorption capacity characteristic of the system and the latter as its enables it to cope with the threat, and together negative antonym. Thus, resistance, absorption (in combination) determine its (in-)sensitivity. capacity, robustness, flexibility, responsiveness and •  daptive capacity refers to the system’s ability A adaptive capacity are related to resilience, while to change deeply and substantially to adapt sensitivity, fragility or rigidity belong to the field of to the impacts of a disaster, which allows the vulnerability. It should be noted, however, that system to return to a satisfying operating state vulnerability analysis covers a slightly broader field, despite the considerable damage caused by a as it also includes the examination of the systems’ shock or high magnitude change. exposure to hazards. 21 22 Hazards and vulnerability in coastal social-ecological systems  ising sea level and storms 1. R cause overtopping  each and dune overtopping 2. B by the highest waves 3. Flooding of residential areas  ong-standing large dam, 4. L managed in such a way that it cannot reduce river flooding at the end of the rainy season  looding of estuarine 5. F agricultural areas by a combination of river flooding and high sea level  rosion of cliffs endangers 6. E buildings 3 2 4 1 5 6 Illustration by Laurent Corsini Senegal. Photo: Vincent Tremeau/World Bank 23 Senegal. Photo: Vincent Tremeau/World Bank 24 GEOGRAPHICAL AREA 2.  OF THE STUDY Ghana. Photo: Hen Mpoano The West African and Gulf of Guinea coasts described here are categorised into three regions with mostly common geo-environmental properties and meteo-ocean forcings: -  he Northwest - Mauritania, Senegal, and Gambia. T -  The West coast - Guinea-Bissau, Guinea-Conakry, and Sierra Leone. - The Gulf of Guinea - Liberia to Côte d’Ivoire, Ghana, Togo, Benin, and Nigeria.  In addition to the 12 countries listed, it is also relevant to consider the presence of two archipelagos lying off the coast; Cape Verde, consisting of 10 islands located 650 km off the coast of Senegal, and the São Tomé and Príncipe archipelago, consisting of two islands located in the trough of the Gulf of Guinea, some 230 km off the coasts of Gabon and Equatorial Guinea respectively. Thus, the scope of this study includes 14 West African coastal countries, which are part of the West Africa Coastal Areas Management Program (WACA). The next sections highlight geomorphological characterisation, meteo-oceanographic drivers’ characterisation, socio-economic context characterisation and the influence of human-induced pressures on coastal territories. 2.1. GEO-ENVIRONMENTAL CHARACTERISATION The 14 countries cover about 6,000 km of a dynamic and mostly soft coast, composed of mangrove forests, mud, sandy beaches, sandy spits, rocky beaches and estuaries (Anthony 2006; Dada et al. 2020). West Africa presents a rich coastal geomorphic variability from the narrow continental shelf, sandy dune-bound coasts of Mauritania, Senegal and Gambia, with common narrow spits bounding estuaries. There is one exception, namely the large Gambia River ria and its southern adjacent cliff- bound coast. The transitional muddy Guinea/ Guinea Bissau/northern Sierra Leone sector is known for cliff-bound coasts and open estuaries rich in seafront mangroves. This is as a result of strong wave dampening and tidal range amplification generated by the considerable increases in continental shelf width related to the shelf’s geological offsetting by the Guinea 25 and Sierra Leone fracture zones. From southern small but numerous estuaries, guarantee a sediment Sierra Leone to the Niger Delta there is a narrow shelf, load, which increases water turbidity leading to bounded by massive rectilinear sandy beach- ridge shoreline accretion in certain areas (Anthony 1995, complexes with diverted river systems and back- 2006) and contrasts with the sandy beaches of West barrier lagoons. Africa. The Liberian coast is low lying with a number of deposition and erosion characteristics, such as sandy  he Northwest - from 2.1.1. T beaches, lagoons, estuaries, mangroves and rocky bottoms (Ssentongo 1987). Mauritania to south of Senegal (Casamance) The Gulf of Guinea - from 2.1.3.  The coast of Mauritania, mostly flat in the north, is Liberia to Nigeria an enormous, dry plain broken by sporadic ridges The Côte d’Ivoire coastline presents two different and cliff-like outcrops. The coastal area varies typologies, from Cape Palmas to Fresco, the coastal between high energy beaches in the north and the strip is rocky, while from Fresco to the Ghanaian mangrove environment at the mouth of the Senegal border, the coast associated with a sinking area is low River. Nouakchott, a port constructed in 1986 is the lying with respect to the 100-m contour, sandy, and most exposed to coastal hazards. The protective surrounded by lagoons. Côte d’Ivoire’s continental structure, including a dam constructed in 1987 in shelf is narrow, about 20-25 km with a submarine Nouakchott, and a groyne built in 1991 to protect canyon off Canal de Vridi, also known as Trou Sans the coast, have begun to break down with erosion Fond (Allersma and Tilmans 1993; Giardino et al. rates of about 25 m/year observed in the area. 2018). Côte d’Ivoire’s coastline is also characterised Senegal and Gambia’s coastal areas encompass by a steep coast, rocky outcrops and pocket beaches. a wide variety of ecosystems, including long sandy beaches, volcanic rocky areas (Cape Verde Peninsula) Ghana’s coastline is 540 km (Boateng 2012) and using and particularly large estuaries at the mouths of the the coast’s morphological features, is subdivided Senegal, Saloum, Gambia and Casamance Rivers. into main sectors - the eastern, central and western In the Senegal and Saloum Estuaries there are large coastal areas. Nearly 149 km of the east coast covers spits and barrier beaches. Due to oceanographic and the area between Aflao at the border of Togo and climatic conditions or to anthropogenic actions, these Prampram, which is predominantly sandy with barrier geomorphological sand structures are mobile and lagoons and spits (Angnuureng et al. 2013), where capable of endangering inhabited areas (Kane et al. sediment particle size range from medium to coarse. 2013). For example, the Ndiago community around Saint-Louis, Senegal, is at risk (UNESCO-IOC 2012) The central coast is categorised by moderate energy, due to erosion and there are also several wetlands, a pocket coast of rocky headlands, sandbars and mangroves and sandy islands in the estuaries where spits enclosing coastal lagoons (Angnuureng et salinisation affects agriculture in some areas (Faye et al. 2020). This coast consists of rocky headlands, al. 2019). Coastal erosion is a general phenomenon sandbars and spits, bordered by sporadic coastal that strongly affects the low coasts of Senegal and lagoons. The central coast is more developed than Gambia, and from 1968 to 1986, these coastal areas other areas, extending from Prampram to Cape Three were characterised by accretion. The opposite was Points with a coastline of approximately 296 km. The observed between 1986 and 2004, when records sandy shorelines along the coast lie mostly among show a greater recession. The recession remained rocky headlands and other promontories. as a decisive element of the coast between 2004 through 2017, though at a slower retreat scale From the estuary of the Ankobra River to the border (Thior et al. 2019). For many years now this region is with Côte D’Ivoire, the west coast is 95 km long facing a decline in the coastline, the consequences and comprises of flat but wide beaches bordered of which remain significant both environmentally and by lagoons and characterised by low energy events. socioeconomically. Coastal erosion occurs to a varying extent along the entire Ghanaian coastline (Blivi et al. 2002). The coastlines of Togo and Benin lie at the centre of a  he West coast - from 2.1.2. T continuous and uniform system of dune ridges and Guinea-Bissau to Sierra lagoons in the Bight of Benin which extends west to east from the Volta River Delta in Ghana to the Leone western side of the Niger River Delta in Nigeria (Blivi The coast from Guinea-Bissau to central Sierra Leone 1993). The Bight of Benin coast represents one of is an example of a mud-dominated coast supporting the longest global systems of beach-ridge barrier- large areas of mangroves, and with rice fields where lagoons and expands mostly uninterrupted across mangroves were cleared to make way for agriculture several estuarine re-entrants over nearly 300 km (Anthony 2006). Although this area lacks major rivers, along eastern Ghana to western Nigeria (Boateng 26 2012). Until recently, the sandy beaches of Togo and with two main islands of the same name. The coastal Benin were mainly fed by sedimentary inputs from the zone includes the slopes of extinct volcanoes within Volta and Mono Rivers, which were then redistributed which the environment is under pressure from soil through a powerful west-east coastal drift (Rossi degradation and coastal erosion. 1989). From the 1960s on, the balance of this coastal geological system was totally disrupted as a result of anthropic actions (Ozer et al. 2017). Sediment budget METEO- 2.2.  considerably changed due to the reduction of fluvial OCEANOGRAPHIC sediment inputs following the construction of dams on the two main rivers feeding the coast (Mono and Volta DRIVERS Rivers) and the development of ports and harbours in Cotonou and Lomé which changed coastal sediment 2.2.1. The Northwest transport (Ozer et al. 2017). Only 34 per cent of the The northwest swell is oblique to the Senegalese Togo and Benin coastlines are stable with accretion coast and drifts from north to south throughout the observed updrift of harbour infrastructures. Other year on southern coasts (Faye 2010; Sadio et al. 2017; stretches of coastline undergo erosive processes Thior et al. 2019), where the formation of coastal spits (52 per cent) and from time to time exceed annual and sandy ridges extend towards the south. Within average retreats of 10 m/year. In such conditions the northwest coast, particularly in Senegal, hindcast over the past decade villages disappeared and a wave data retrieved from Wave Atmospheric Model large number of people displaced (Ozer et al. 2017). and the European Re-Analysis between 1984 and Benin consists of low-slope sandy beaches with 2015 reveal that the wave regime is a mixture of swell marshes and shallow lagoons. The areas to the west and wind waves (Sadio et al. 2017; Ndour et al. 2017). include the Grand Popo lagoon, separated by only The Era-Interim, a global atmospheric re-analysis a few dozen meters from the ocean and a hot spot available from 1 January 1979 to 31 August 2019 and of erosion (Boateng 2012). The coastal area around a product of the European Centre for Medium-Range Cotonou reflects the predominant sand movement Weather Forecasts, was used to calculate average from west to east, visibly creating sand accumulation periods between 1984 and 2015. This method records west of the port and erosion to the east (Almar et al. significant annual swells and wind wave heights (Hs) 2015). The city of Cotonou itself is prone to flooding of 1.5 m and 0.5 m respectively, with maximum peak due to poor drainage and land subsidence. The swell and wind wave periods of 9.2 s and 3.0 s where loss of natural habitat on the coast leads to a loss the main wave direction from WNW to N (Ndour et al. of biodiversity and natural services such as wetlands 2017; Almar et al. 2019) and the range of wind wave for flood control, recreation and tourism areas or, in direction is larger. Its influence is especially noticeable the case of mangroves, protection against coastal throughout the north direction of sand dunes on the erosion. The littoral area of Nigeria comprises four Casamance and Gambian coasts. The wave direction different geomorphological components with about shows momentary oscillation in August dominated 853 km coastline - the barrier-lagoon complex, the by the south swells (Almar et al. 2019) where wind mud coast, the arcuate Niger Delta and the Strand waves show a much wider directional window. There Coast (Ibe 1988; Dada et al. 2020). The Niger Delta is a clear seasonal modulation with maximum wave (approximately 284 km) is one of the largest arcuate activity during winter in the northern hemisphere, with fan-shaped river deltas in the world, situated south of strong storm activity in high and mid-latitudes. Wind Nigeria along the Gulf of Guinea coast from the west waves also show greater daily and monthly variability. Ramos River entrance to the east Sombreiro River Unlike swell waves, wind waves are carried by local entrance. Since 1956 there has been an increase in oil tropical winds and show peaks in spring and autumn exploitation in the area, especially in the villages along which correspond to the passages of the Inter- the Niger River Delta. This coastal area is low-lying, Tropical Convergence Zone over Senegal. The distant with elevations limited to 3.0 m above sea level and is high latitude oblique energy waves cause one of the largely covered with freshwater swamps, mangroves, highest coastal drifts in the world (~800,000 m3/year lagoons, tidal channels, beach ridges and sand bars. in Saint-Louis, Sadio et al. 2017). The tidal regime is mostly semi-diurnal, and tide amplitude varies between 0.5 m at neap tides to 1.6 m at spring tide. 2.1.4. Archipelago component From a geological perspective, the Cape Verde archipelago is mainly composed of igneous rocks, 2.2.2. The West coast with volcanic structures. On the coastlines of Cape The muddy coast from Guinea-Bissau to Sierra Leone Verde, though erosion probably affects a number of is oriented SE-NW (Anthony 1989, 2004, 2006) which islands, there is no information on the intensity of is a major junction coast in terms of wave climate erosion rates (UNESCO-IOC 2012). in the region (Anthony 2006) and exposed to swell waves from the North and South Atlantic. This coast São Tomé and Príncipe consists of an archipelago 27 Guinea. Photo: Vincent Tremeau/World Bank experiences northwest waves of low to moderate short waves in the tropical band (6°N - 15°S). The energy, with offshore water heights less than 1.2 m for swell waves are more conspicuous during the rainy about 70 per cent of the time and southwest waves season (June to September), with extensive sediment between 1 and 3 m. The wave climate comprises dispersal towards the coast. The mid- to high latitude annual dominant long period swells (T = 8-16 s) mixed wind is characterised by strong westerly winds, while with seas (T = 7-5 s) from the northwest, and mixed the subtropical zone (30°S - 35°S) is dominated by swells and trade-wind waves (T = 8-12 s) from the south easterly trade winds blowing off the coast of southwest, which are periodically dominant between Namibia (Almar et al. 2015). South-westerly swells are June and October (Anthony 2006). Maximum Hs slightly oblique at angles of 10°-15° on the Bight of during the higher-energy season of south westerly Benin coast where the tidal regime is microtidal, with waves do not exceed 1 m. The tides in the area are 0.3 m and 1.8 m for the neap and spring tide ranges semi-diurnal with meso-macrotidal range (with mean respectively. tidal range of 3-5 m) which shows a south-north increase hinged on the shelf’s width and geometry. Generally, the entire West African coastal area of concern is cyclone and storm free, even though swells from distant tropical cyclones can hit the coast (Almar 2.2.3. The Gulf of Guinea et al. 2019). The Gulf of Guinea coast includes Liberia, Côte d'Ivoire, Nigeria, Ghana, Benin, Togo to São Tomé and Príncipe, which stretches over 2,000 km between 7˚30  OCIOECONOMIC 2.3. S W and 9˚ E and includes the Bight of Benin between CHARACTERISATION Ghana and Nigeria (Laïbi et al. 2014; Almar et al. 2014, On the coast of West Africa and the Gulf of Guinea, 2015). The Gulf of Guinea coastal wave climate is the human footprint is strong in relation to the characterised by two contrasting components - locally concentration of population and economic interests. generated wind waves and a dominant component of The 14 coastal countries population of West Africa long, medium- to high- latitude swells. The Bight of and the Gulf of Guinea (from Mauritania to Nigeria, Benin is an open environment exposed to long swell including the islands of Cape Verde and São Tomé) waves travelling from the mid- to high latitudes (45° - was 320.3 million in 2018 (https://data.worldbank. 60°) in the South Atlantic, as well as locally generated org/indicator) and is growing at an average annual 28 Figure 2. West Africa population evolution. Data extracted from UN - Division of the Department of Economic and Social Affairs (2018) comprising the following West African countries: Benin, Burkina Faso, Cabo Verde, Côte d'Ivoire, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra Leone and Togo. rate of 2.58 per cent. About half of this population is Lagos, a coastal metropolis and the largest city in (159.5 million) is considered urban, and more than Africa, which is also one of the fastest growing cities a quarter (84.5 million) live in a large city of more in the world. The population of Lagos grew from 3.3 than 1 million. There are 28 large cities in this area, million in 1975 to over 13 million in 2001 and 22.9 of which 14 are located on the coast accounting for million in 2017 and now represents about 12 per cent 49.2 million inhabitants. The West African Economic of the national total, (UN Population Division, 2018). In and Monetary Union commissioned an assessment general, rapidly growing coastal cities such as Lagos in 2016 of West Africa Coastal Areas indicating that (Nigeria), Accra (Ghana), Abidjan (Côte d'Ivoire) and coastal areas (here considered on a 25 km fringe Dakar (Senegal) all have annual growth rates of 4 per depth) gather 31 per cent of the total population and cent or more. 51 per cent of the urban coastal states’ population. Senegal, Gambia and Guinea-Bissau are continental Communities living below 5 metres are considered West African countries where 80 to 100 per cent of a proxy when looking at vulnerability of populations the population live within 100 km of the coast, and closely associated with the coast and vulnerable to this characteristic is also true for the two archipelagic change in sea levels. In the 14 countries studied the countries - Cape Verde and SãoTomé and Príncipe. population living at very low altitude represents 4.2 More generally, when considering the total population per cent of the total population (2010 estimate), so of West Africa, more than a quarter of the population using the estimates for growth rates would mean the live within 100 km of the coast (UN-Habitat, 2014). equivalent in 2018 is 13.3 million. The corresponding low altitude areas represent only 1.02 per cent of the This concentration of population on the coast is due to surface area of these countries. It follows that in the natural demographic dynamics ‘on location’ but also low areas (alt < 5 m, generally close to the sea), the the result of a migration event in rural West Africa from average human density reaches 387 inhabitants/km2, the hinterlands towards the coastal regions. In part, while the average density is just 95.2 inhabitants/km2 this movement can be seen as a flight of populations if the whole region is considered (all figures estimated in the face of the Sahel crisis, notably the great drought from https://data.worldbank.org/indicator). between 1973 and 1993 and more recently since 2012 with the rise in insecurity in rural areas of Mali, Niger However, the population’s distribution along the coasts and Burkina Faso. This phenomenon is continuously are marked by strong contrasts (UEMOA, MOLOA, fuelled by the strong natural demographic growth of UICN, 2017) where there are still large stretches of the inland Sahelian region and accentuated by the coastline that remain natural and ‘wild’, occupied by economic lure of capital and large coastal cities, which mangroves or sandy beaches where small farming are characterized by the presence of employment and fishing villages settled. Conversely there are opportunities (industrial, port and service activities) relatively few but large urban centres characterized by and by a ‘modern’ consumption model. high population growth and rapid spatial expansion, increasingly encroaching on adjacent natural coasts. It follows that the demographic growth of large coastal From the Gambia to the west of Côte d’Ivoire, the cities is much higher than the maximum potential coast is predominantly wild with a few large cities natural growth rate (births minus deaths), as it reaches spread out. On such tracks of coastlines, human 4.6 per cent per year on occasion. A good example density is normally low with 10 inhabitants/km2. 29 Population Annual Surface area Population Land area Population living in areas Population (in millions - population (sq. km, density elevation below 5 meters with elevation below 5 meters density in 2018) growth rate thousands) (people per area below % (2010 - km sq, in % of land Sq km unit % of total In millions 5 meters 2018) 2018) area population (updated (people (estimated in 2018) per km sq, 2010) updated 2018) Mauritania 4,4 2,9 1030,7 4 1,1 11337,7 19,1 0,84 74,1 Cabo Verde 0,5 1,3 4,0 135 3,6 144,0 5,6 0,03 194,4 Senegal 15,9 2,7 196,7 82 3,5 6884,5 10,1 1,61 233,3 Gambia, The 2,3 3,0 11,3 225 16,8 1898,4 23,5 0,54 284,7 Guinea- 1,9 2,5 36,1 67 6,5 2346,5 15,3 0,29 123,9 Bissau Guinea 12,4 2,3 245.9 51 0.9 2213,1 6,0 0,74 336,2 Sierra Leone 7,7 2,8 72,3 106 2,9 2096,7 3,8 0,29 139,6 Liberia 4,8 2,9 111,4 50 0,3 334,2 6,4 0,31 919,2 Cote d'Ivoire 25,1 2,3 322,5 79 0,3 645,0 3,8 0,95 1478,8 Ghana 29,8 2,4 238,5 131 0,6 1431,0 2,6 0,77 541,4 Togo 7,9 2,6 56,8 145 0,4 227,2 3,6 0,28 1251,8 Benin 11,5 2,9 114,8 102 1,0 1148,0 11,9 1,37 1192,1 Nigeria 195,9 2,6 923,8 215 0,4 3695,2 2,7 5,29 1431,4 São Tomé 0,2 2,2 1,0 220 0,9 9,0 1,3 0,00 288,9 and Principe Overall 320,0 2,58 3365,8 95,2 1,02% 34410,5 4,2% 13,3 387,2  opulation characteristics and areas of West Africa for 14 coastal countries, with emphasis on the figures for land below 5 meters. Data from World Table 1 : P Bank website https://data.worldbank.org/indicator (accessed March, 2020, 30th) However, from Abidjan in eastern Côte d’Ivoire to on coastal and marine resources (Celliers and Port Harcourt in eastern Nigeria, there is a series of Ntombela, 2015). According to the UN Environmental large cities which reduce the space in natural intervals Programme/Nairobi Convention Secretariat and the (Glasser and Farvacque-Vitkovic 2008). The latter Western Indian Ocean Marine Science Association is likely to become a continuous urban megalopolis (2009b), some specific links between urbanisation (Post and Lundin 1996) with average densities already and coastal environmental quality include: reaching up to 1,000 inhabitants/km2 along the Togo •  ater quality degradation is caused by alteration W and Benin coasts (UEMOA, MOLOA, UICN, ibid). of natural river flow, changes in fresh-water input and sediment load; the degradation of HUMAN-INDUCED 2.4.  ground and surface water quality; microbiological contamination from land-based sources mainly PRESSURES domestic, industrial, agriculture and livestock Urbanisation along the West African coastline as well as marine including aquaculture and increased pressures in coastal and marine ecosystems shipping sources; and solid waste/marine debris, to alarming levels. This is particularly the case in Côte for example plastics deposited from shipping and d’Ivoire, Ghana, and Nigeria, where coastal areas host land-based-sources. an array of industrial activities ranging from textiles, •  abitat and community modification caused H leather, food and beverage processing industries, to by shoreline change due to modification, land extraction and processing of petroleum, natural gas, reclamation and coastal erosion; disturbance, phosphates, and other minerals (World Bank, 1996). damage and loss of upland/watershed habitats Major watersheds encompassing river systems in (>10 m elevation); disturbance, damage and loss Gambia, Niger, and Senegal are seriously threatened of coastal vegetation and floodplain habitats (to by ecosystem degradation, and globally significant 10 m elevation); disturbance, damage and loss biodiversity is at risk. of mangrove habitats, coral reef habitats and seagrass habitats; and the introduction of exotic The use and conversion of coastal land, urbanisation, non-native, invasive and nuisance species. population growth, demographic shifts, poverty and a lack of alternative livelihoods, increased wealth, • A  decline in living marine resources including urbanisation and consumption rates (for example, populations of prawn, shrimp and reef and building material, fish) intensifies the demand demersal fish. 30 Senegal. Photo: Liliane Assogba Sessou/IUCN COASTAL MANAGEMENT 3.  PRACTICES AND SOLUTIONS The complex and interconnected challenges facing the world’s coastal zones require solutions that bridge science and practices and integrate a range of stakeholder perspectives (Vinhateiro et al., 2012). The next generation of coastal practitioners will therefore need a wide-ranging set of problem-solving skills and the ability to collaborate across disciplines. As part of the objectives of the WACA Program including participants from multidisciplinary backgrounds, the complex issues of coastal ecosystem management are key. This report discusses aspects of coastal management practices that exist in West Africa or could be applied as coastal management solutions. Fundamentally, this section of the compendium focuses on methods implemented to maintain beaches, prevent hazards, and address socio-economic aspects and governance challenges of coastal environments. The opportunity to utilise multidisciplinary knowledge while working with a broad network of researchers under this project brought quality information to enable assess to best practice. In the following chapter, the main technical options for managing erosion and flooding risks are presented according to the classification developed in this report’s introduction. Each option is described generically, before weighing the pros and cons and giving examples of applications in West Africa (if relevant). 31 HARD ENGINEERING 3.1.  and the distant Akosombo Dam in Ghana had a dramatic role in perturbation of the longshore SOLUTIONS sediment dynamics along the western Bight of Benin (Anthony and Blivi, 1999). Togo faced a number of 3.1.1. Breakwaters coastal issues including shoreline change, flooding, pollution, and the potential effects of a rise in sea General presentation levels where the beach was eroding at an average Offshore breakwaters are shore-parallel hard rate of about 7 m/year (Blivi, 1993) while 12 km of the engineering protection structures situated coast between Kpeme Gumukope and Aneho was just offshore of the surf zone and designed to protected by breakwaters (Blivi, 1993). As part of the intercept and reduce incoming wave energy at the Benin sea defence project a 300 m-long breakwater shoreline, thus reducing erosion (Finkl and Walker, was constructed by Baird construction to protect 4.5 2005). This ensures accumulation of sediment in the miles of coastline which eroded up to 762 m over a structure’s lee, which leads to beach widening while 40 year period. the construction of shorter breakwaters in series allows for some wave action at the coast which can Other sites where breakwater projects were be beneficial for recreation. The protective function installed include the Abidjan Port Expansion Project of breakwater infrastructure can be maintained for - Breakwater Project in the Côte d’Ivoire coast. The many years, requiring only basic monitoring and project contractors, China Harbour Engineering maintenance if properly planned, designed and Company Ltd. and CCCC First Harbour Engineering constructed. In West Africa, breakwaters are mostly Co., Ltd used construction methods which included implemented in harbours for the purpose of reducing demolition and reconstruction of the east and west wave actions for ships. breakwaters at the entrance of the fairway. The project aimed to further enhance the status of Abidjan Port as West African case studies a hub port on the Atlantic coast of Africa and promote economic and social development in Côte d'Ivoire The deep-water port of Lomé, inaugurated in 1967, and throughout West Africa. Solution n°1: Breakwaters Category Hard engineering solutions [ X ] Soft engineering solutions [ ] Coastal planning & risk management techniques [ ] Compliance with nature-based solution criteria: Yes [ ] Maybe, under certain conditions [ ] No [ X ] Substance and Purpose Offshore breakwaters are shore-parallel hard engineering protection structures situated just offshore of the surf zone and designed to intercept Breakwaters in Saly, Senegal. Photo: Senegal World Bank funded and reduce incoming wave energy at the shoreline, Tourism Project (PDTE) thus reducing erosion. This ensures accumulation of sediment in the lee of the structure, leading to Assets, advantages and strengths particular to widening of the beach. the West Africa coastal area Main environmental requirements The shorter breakwater construction in series & institutional context allows some wave action at the coast, beneficial for Breakwaters are expensive, requiring a high level recreation. The breakwater protective function can of technical knowhow. Appropriate only in certain be maintained for many years, requiring only basic current and wave conditions. monitoring and maintenance if appropriately planned, designed and constructed. Combining with other solutions Breakwaters aim to be sufficient as a stand- Constraints, weaknesses and difficulties alone method to protect a stretch of coastline. particular to the West Africa coastal area Nevertheless, may be combined with other type of A preliminary survey to understand the area's wave defense structures such as jetties. dissipation is required. 32 3.1.2. Groynes Potential collateral effects and General presentation other disadvantages The primary disadvantage of groynes is that the Groynes are narrow, shore-perpendicular, hard interruption of longshore drift to promote beach structures designed to interrupt longshore widening on one section of coastline is likely to cause sediment transport through trapping a portion of sediment starvation and erosion further downstream. the sediment, otherwise transported alongshore As groynes do not add sediment to the shoreface but (Appelquist et al., 2016). These are solid, durable rather distribute available materials differently, groyne structures and considered a hard- engineering construction then is perhaps most effective when protection measure to address coastal erosion. complemented by beach nourishment. Groyne fields are commonly located on drift-aligned By promoting sediment build-up on the updrift side coasts where erosion difficulties are generated by of the groyne there is a consequent sediment deficit gradients in longshore transport (in contrast to erosion on the downdrift side, requiring the construction of issues caused by cross-shore transport) (Kristensen further groynes to maintain beach width. At the most et al., 2016; Scott et al., 2016). An ideally designed downdrift extent of a groyne field, a symptom known groyne field allows sediment to accumulate and as ‘terminal groyne syndrome’ often exists, where eventually bypass the buried groyne, without causing sediment starvation causes accelerated erosion of significant downdrift erosion. However, an ideal design the unprotected coastline with obvious negative is rarely achieved due to lack of detailed data on wave implications. climate and longshore sediment transport rates (Davis Jr and Fitzgerald, 2004). West African case studies The dimensions between groynes’ length and spacing Groynes to control coastal erosion is the most generally varies from 1:4 on sandy beaches to 1:2 on popular method practised in the subregion from gravel beaches. Groynes’ length are ideally 40-60 per Senegal to Nigeria. cent of the average surf zone width in order to trap some, but not all, of the littoral drift (Masselink and Erosion in the Keta area began between 1870 and Hughes, 2003). Groynes can help stabilise beaches 1880 after the sea removed 200 to 300 m of land near but if constructed too close together then sediment central Keta, located on the eastern part of the Volta can be washed offshore (Charlier and Meyer, 1998) River estuary. The recession at the mouth of the Volta increased from 4 m/year to 8–10 m/year following Sediment characteristics play a part in groyne the construction of the Akosombo Dam across the design with longer groynes typically employed where Akosombo River, preventing 99.5 per cent of the sediments are smaller. As smaller sediments are river's sediment from reaching the sea (Ly, 1980). typically mobile at greater water depths, consequently Since then, various protective measures taken to groynes are less effective at retaining finer material stabilize the coast did not yield the desired results. (Brampton, 2002). A steel wall made of sheet piles was built between 1955 and 1956 but collapsed in the 1960s. From While groyne field construction requires a good 1976 to 1978, temporary measures including the use degree of expertise, its use has been widely applied of rocks in revetments to protect the Fort of Keta, for decades across the globe. Consequently, there produced negative results when rocks sank into the is broad global experience with groyne design and sandy material due to the absence of appropriate construction. filter material under the lining. After several years of studies on coastal erosion in Keta, the Government Key benefits of Ghana finally accepted the American Great Lakes One of the main advantages of groynes is the Construction Company’s proposal to design and build ability to trap sediment, resulting in beach widening seven riprap groynes to stabilise a coastal stretch of with reduced erosion and greater wave energy approximately 7.5 km. Since the completion of the dissipation as a consequential benefit. Groynes also project, the coastal stretch was stabilized on the updrift complement other management practices, such as and secured, enabling construction of structures, seawalls, revetments, beach nourishment and dune including creating social amenities for communities construction by reducing wave energy through these previously highly vulnerable to severe wave surges. structures. By fostering beach widening, groynes However, the result of using a combination of groynes maintain an attractive beach environment, which can and revetments in the Keta sea defence construction be valuable for recreation and tourism. led to increased coastal erosion on the down-drift coast towards the Ghana–Togo border. Additionally, the Government of Ghana is carrying out several major sea defence projects at sites considered 33 highly vulnerable. These include the Ada Sea Defence edge of the port, the coast receded by approximately Project, Sakumono Sea Defence Project, the New 500m over the same period. The high cost of the Takoradi Sea Defence Project, the Elmina Sea Defence project prevented its completion in accordance with Project, which are all spread along the coastline but specifications. Materials used consisted of gabions, these site-specific interventions have knock-on effects rock of various size and geotextile filter. As a pilot in most of the adjacent beaches. project, it was necessary to monitor the site in order to adjust design parameters, however, the necessary The project for erosion control in Cotonou was readjustments were not carried out, and the project designed as a prototype, in the hope of replicating in was eventually abandoned due to serious defects and other parts of West and Central Africa and involving the lack of routine maintenance of partially completed the construction of five short and low height groynes in structures. These examples illustrate the need to Cotonou, Benin's capital. The objective was to stabilize gather all the relevant data and carry out specific the shoreline in front of a new residential area which on-stie investigations to determine the validity of the suffered a marked coastline decline at a rate of 2 - 3 m/ chosen technical solution. year. In 1988, the shoreline advanced approximately 650 m on the western edge of the port, which is the current site of the Sheraton Hotel, while on the eastern Solution n°2: Groynes Category Hard engineering solutions [ X ] Soft engineering solutions [ ] Coastal planning & risk management techniques [ ] Compliance with nature-based solution criteria Yes [ ] Maybe, under certain conditions [ ] No [ X ] Substance and Purpose Groynes are narrow, shore-perpendicular, hard structures designed to interrupt longshore sediment transport by trapping a portion of the sediment which is otherwise transported along shore. Groynes are generally solid, durable structures and considered a protection measure to address coastal erosion. Main environmental requirements & institutional context Groynes in Saly, Senegal. Photo: Senegal World Bank funded Appropriate for drift-aligned coasts where erosion Tourism Project (PDTE) difficulties are generated by gradients in the longshore transport. Groyne field construction Constraints, weaknesses and difficulties requires a good degree of expertise. particular to the West African coastal area Combining with other solutions The primary disadvantage of groynes is the Groynes complement other solutions such as interruption of longshore drift to promote beach seawalls, revetments, beach nourishment and dune widening on one section of coastline, which is likely construction by reducing wave energy at these to cause sediment starvation and erosion further structures. downstream. Groynes don’t add sediment to the Assets, advantages and strengths particular shoreface but rather distribute available materials differently. As such, groyne construction is perhaps to the West Africa coastal area most effective when complemented with beach The advantages of groynes are mainly related to nourishment. their ability to trap sediment, thereby leading to beach widening with consequent benefits of reduced erosion. 34 3.1.3. Jetties accumulation in an inlet or river mouth. Consequently, sediment accumulation typically occurs on the updrift General presentation side and sediment starvation on the down-drift Jetties are typically larger, extend greater distances (Masselink and Hughes, 2003). offshore than groynes and constructed from a wide Jetties can be very long, frequently leaving large variety of materials including rock armour, concrete, quantities of sediment trapped on the updrift side, dolos, tetrapods and steel piling. which can lead to major coastline setbacks on the Jetties are hard structures constructed at the down-drift side (Davis Jr and Fitzgerald, 2004). As with banks of tidal inlets and river mouths to trap a groynes, the formation of rip currents in the adjacent portion of longshore sediment transport. This area should be expected. With jetties typically longer results in stabilising inlets and prevents channel than groynes there is an expectation that this would siltation, thus ensuring navigation (Appelquist et al., lead to greater sediment loss to deep water during 2016). By stabilising natural features, jetties contribute storm events (Masselink and Hughes, 2003). to the development of stable environments suitable When planning jetty construction, long-shore sediment for social development. transport is a critical design parameter. It may be necessary to combine construction with a sediment Key benefits bypassing scheme, where sediment trapped by the Jetties are long term solutions to coastal protection and jetty is dredged from its updrift side and deposited beneficial when coastlines are already developed with on the downdrift side of the tidal inlet/river mouth. infrastructure and property. The principal advantage This would maintain a degree of longshore sediment is to ensure the continuous passage of ships through supply and could be implemented alongside channel a tidal inlet or river mouth - a significant benefit for dredging, often required for maintenance of a development and commerce. The installation of jetties navigable channel. is often associated with harbours. West Africa case studies Potential collateral effects and Jetties are found at eroding tidal inlets of the Elmina other disadvantages Benya lagoon entrance into the sea (Ghana), at the Like groynes, jetties are designed to interrupt long- Takoradi harbour, at Cotonou Port and other areas shore sediment transport, preventing sediment along the Bight of Benin. Solution n°3 : Jetties Main environmental requirements Category & institutional context Hard engineering Costly to construct, hence limited to developed solutions [ X ] coastlines with infrastructure (harbours). Soft engineering Combining with other solutions solutions [ ] Coastal planning & It may be practical to combine jetty construction risk management with a sediment bypassing scheme, where sediment techniques [ ] trapped by the jetty is dredged from its updrift side and deposited on the downdrift side of the tidal inlet/river mouth. This would maintain a degree of Jetty of Takoradi harbour, Ghana. longshore sediment supply. Photo: Google Earth Compliance with nature-based Assets, advantages and strengths particular to solution criteria the West Africa coastal area Yes [ ] Jetties are long term solutions to coastal protection Maybe, under certain conditions [ ] and can be very beneficial in areas where the No [ X ] coastline is developed with infrastructure and property. The principal advantage is to ensure the Substance and Purpose continuous passage of ships through a tidal inlet or Jetties are larger, extend to greater offshore distances river mouth where there are significant benefits for than groynes and constructed from a wide variety development and commerce of materials including rock armour, concrete, dolos, Constraints, weaknesses and difficulties tetrapods and steel piling. They are constructed at the particular to the West African coastal area banks of tidal inlets and river mouths to trap a portion of the longshore sediment transport, stabilising As jetties can be long structures, considerable the inlet and preventing channel siltation, ensuring amounts of sediment can be trapped on the updrift navigation. side, which can lead to major coastline setbacks on the downdrift side. 35 Benin. Photo: ABE 3.1.4. Revetments safe for leisure project development. The section of the beach underwent an average erosion rate of 7.5 General presentation m/year, which led to a suspension of development Revetments are shore-parallel, sloping structures, projects in the area. The construction which began constructed landwards toward the beach to dissipate in 1982, was made of rock-filled gabions and the and reduce wave action on the boundary between first time that gabion technology was used to solve the sea and land (Appelquist et al., 2016). These coastal erosion in Ghana. The Labadi shoreline structures typically protect soft landforms such as protection project, which involved 1,600 m of beach, dune areas or coastal slope or provide supplementary was organised around three steps which gradually protection to existing defences such as a dyke or led to mastering the technique. After completion of seawall. Revetments are generally solid, durable the gabion revetment structure, the beach is now structures and considered as hard engineering, protected from wave swells where the bathymetry typically employed on the seaward edge of coastal of the submarine beach has flattened, providing a sections vulnerable to erosion, such as dunes, soft greater sense of safety. cliffs or other defence measures. Saint-Louis’s coastal community, on the northern edge of Senegal’s Atlantic coast, is losing ground to West Africa case studies the ocean each year. Families are losing possessions, A revetment of 100 m long was built between 1959 food and homes to coastal erosion, flooding and and 1960 at Jamestown, Accra, Ghana as part of frequently breaking waves. At a rate increasingly measures to counteract coastal erosion during the worrying to residents and officials, waves overtop construction of the Korle Lagoon spillway, in Accra. buildings on the shoreline, pulling sand away and After 15 years, the revetment was severely assailed by eroding foundations so that walls and floors collapse. overtopping sea waves. The run-up and overtopping The impact is particularly severe on the Langue de affected the road located east of the revetment, with Barbarie, a thin, sandy peninsula which extends over damage to the road between Korle lagoon and central a dozen miles further south and acts as a natural Accra at high tide. To address this, a low cost, low ocean buffer. technology gabion revetment was proposed and constructed between 1983 and 1984, achieving For those on the Langue de Barbarie, the Senegalese remarkable results in the first year to 18 months. The government and the French Development Agency swells, which overtopped the road ceased; substantial contracted Eiffage, a construction company, to build accretion occurred, and it became evident that a revetment to shield houses from the ocean swell. beach profiles were flatter than before the revetment The revetment will consist of giant five-ton bags installation. The main factors responsible for this high of sand topped with rock-filled cages and will run rate of accretion was the flat slope of the revetment for approximately two miles down the coast until it and the effective dissipation properties of the rock- reaches parts of an old colonial-era sea wall, which filled gabion structure. remains standing. Officials stress that the revetment is an emergency buffer to protect houses from Labadi beach, in Greater Accra is an interesting immediate destruction and not a permanent solution revetment paradigm, where the shoreline recession to counter erosion. Some longer-term solutions rate was 3 to 5 m per year between 1955 and 1985. proposed include building breakwaters or a new sea Between 1965 and 1978 the highest recession rate wall, supplying sand to beaches or clearing beaches occurred on 100 m of beach, previously considered to create a buffer zone. 36 Solution n°4 : Revetments Category Main requirements (regarding the Hard engineering solutions environmental or institutional context) [X] Very expensive. Soft engineering solutions [ ] Coastal planning & risk Combining with other solutions management techniques [ ] Other defence solutions including groynes, breakwaters for reinforcement. Compliance with nature- based solution criteria Assets, advantages and strengths particular to Yes [ ] the West African coastal area Maybe, under certain Depending on the local conditions, it may result in conditions [ ] increased accretion and a flatter beach profile, thus a No [ X ] stabilised shoreline. Constraints, weaknesses and difficulties Substance and Purpose particular to the West African coastal area Revetment in Benin. Photo: IUCN Revetments are shore- Takes up space and may impede access to the sea parallel, sloping structures, (for some activities). Even solid, it is not a lifelong constructed landwards of the beach to dissipate and project. reduce wave action. These structures typically protect a soft landform such as a dune area or coastal slope and often solid structures. Revetments are employed on the seaward edge of coastal sections vulnerable to erosion, such as dunes, soft cliffs or other defence measures. 3.1.5. Seawalls in the coastal cell, down-drift erosion for example, flanking erosion, basal scour and beach down-draw General presentation (French 2001; Hansom and McGlashan 2000; French Seawalls are HES with a primary function to 1997; Bird 1996; Kraus and MacDougal 1996; Tait prevent further shoreline erosion (Appelquist et al., and Griggs 1990; Kraus and Pilkey 1988). However, 2016), built parallel to the shore and aim to hold these impacts were known for more than a century as or prevent soil sliding, while providing protection illustrated in Owens and Case (1908), and Mathews from wave action. Although the primary function is (1934). Philpot (1984) notes that there was professional erosion reduction, seawalls have a secondary function awareness of the impact on coastal structures for the as coastal flood defences and usually used in areas last 50 years. Despite this, some experts still hold an where further shoreline erosion will result in extreme opinion that building seawalls is a viable option. This damage, for example where roads and buildings are may be due to a lack of awareness of alternatives or about to fall into the sea (Appelquist et al., 2016). a belief that it is a single effective option, coupled with the demand for coastal land. Various examples below Key benefits show that seawalls pose durability challenges. The advantage of a perfect and efficient seawall is its West Africa case studies ability to provide a greater level of protection against coastal flooding and erosion. A well-maintained and Seawalls are used in several parts of West Africa appropriately designed seawall will also fix the boundary including Rufisque, a coastal community in Senegal between the sea and land to ensure no further erosion where two types of walls were constructed in Keuri occurs – this is beneficial if the shoreline is home to Kad and Keuri Souf. The walls were built between important infrastructure or other buildings. Seawalls 1983 and 1990 and stretch for 3.5 km, however a do not take up a great deal of space especially when recent assessment revealed that some sections vertical seawall designs are employed, and the result of the walls were so fragile they had collapsed and is a reduction in construction costs. could not prevent high waves from breaking. Another example is the concrete walls built on gabions in Potential collateral effects and Diokoul, Senegal between 1990 and 1992 (UNESCO/ IOC 2012) and were in a state of failure or collapse. other disadvantages However, rather than seeking alternative solutions, a The general impact of seawalls and other erosion new seawall was constructed before the collapse of management techniques are well documented and the first wall (UNESCO/IOC 2012). can include a general reduction of available sediment 37 Solution n°5 : Seawalls well as preventing Category overtopping waves. Hard engineering solutions [ X ] Assets, advantages Soft engineering solutions [ ] and strengths Coastal planning & risk management techniques [ ] particular to the Compliance with nature-based West African solution criteria coastal area Yes [ ] A perfect seawall can Maybe, under certain conditions [ ] provide a high level No [ X ] of protection against coastal flooding Substance and Purpose and erosion. When Seawalls are built parallel to the shore and aim to well-maintained hold or prevent soil sliding, while providing protection and appropriately from wave action. Their primary function is to prevent designed, seawalls The old seawall of Saint-Louis, Senegal, further shoreline erosion. The secondary function is do not use a large Photo: Bruna Alves/IRD defence against coastal floods. Seawalls are usually amount of space and used in areas where further shoreline erosion will will fix the boundary result in extreme damage, for instance, when roads between the sea and land to ensure no further and buildings are about to fall into the sea. erosion occurs. Constraints, weaknesses and difficulties Main environmental requirements particular to the West African coastal area & institutional context Seawalls may lead to a general reduction of available Very expensive. Requires a solid foundation (rocky) for sediment in the coastal cell, downdrift erosion for durability over the long term. example flanking erosion, basal scour (due to wave- energy focusing on the base of the wall), and beach down-draw. Combining with other solutions Currently, the use of seawalls for coastal erosion prevention are constructed in tandem with groynes. This has resulted in the stability of the seawalls as This approach was also used in Ghana along the Gulf Key benefits of Guinea coast, when a steel sheet piling seawall was constructed in Keta between 1955 and 1956 The sloped seaward edge of dykes leads to greater but stopped in 1960 because of persistent coastal wave energy dissipation and reduced wave loadings erosion. The seawall collapsed rapidly thereafter. on the structure compared to vertical structures. This Currently seawalls to combat coastal erosion are is achieved as the seaward slope forces waves to constructed in combination with groynes and gabions break as the water becomes shallower. Wave breaking preventing waves overtopping and resulting in greater results in energy dissipation, causing waves to lose a stability. significant portion of energy. When waves lose energy, they are less capable of causing harmful effects such as shoreline erosion. By reducing wave loadings, the 3.1.6. Dykes probability of catastrophic failure or damage during extreme events also reduces. General presentation Dykes are hard-engineered structures designed Potential collateral effects and in such a way to allow geotechnic stability under normal and extreme conditions (TAW, 2002). The other disadvantages structures have a high volume which help to The use of dykes as a protection measure prevents resist water pressure, sloping sides to reduce an area from flooding, enabling a continuation of wave loadings, and crest heights sufficient to economic and sociological activities at high water prevent overtopping by flood waters. Their use is levels. Nevertheless, it is important to consider that not intended to preserve beaches, or any adjoining dykes require high volumes in order to resist high water unprotected beaches. Dyke usage is common pressure on the seaward face (Barends, 2003). As a practice in low-lying coastal areas of Bangladesh, result, construction uses large volumes of building Vietnam, Thailand and the Netherlands and are often materials, including sand, clay and asphalt, which can the cheapest hard defence practice when coastal be costly. Another disadvantage is the large footprint land is less valuable (Brampton, 2002). caused by the shallow slopes applied to facilitate 38 wave energy dissipation where construction requires is perhaps most relevant to developing countries. In significant land space. Vietnam, dyke construction costs were shown to vary from US$0.9 million to US$1.6 million per metre rise It must be noted that dykes can be breached if in height, per km length. The variability in these costs overtopped by high tides and waves. The construction can be explained with the high level of maintenance of high dykes can increase the possibility of severe carried out in the Netherlands where dyke maintenance damage and collapse caused by extreme events such is prioritised and well organized, while in many other as storm surge. locations, maintenance programmes are less rigorous. Maintenance costs should be set aside, to ensure that sea-dykes continue to provide the designed levels West Africa context of protection. Information on maintenance costs is Dykes are applied in low-lying areas prone to sea limited, although annual dyke maintenance costs per inundation under extreme conditions, but their linear km of dyke is reported to range from US$0.03 application is not yet applied in West Africa. There are million in Vietnam (Hillen, 2008) to US$0.14 million several low-lying areas along the West Africa coastline in the Netherlands (AFPM 2006). In 2009 raising the where the construction of dykes could contribute height of dykes is reported to cost from between greatly to protect the hinterland and population. US$0.9 million to US$29.2 million per metre rise, per However, it is mandatory to analyse the economic km length (Hillen et al., 2010). The Vietnamese cost feasibility to construct and also cost the maintenance of dyke construction, highlighted in the Hillen reports of such an expensive coastal engineering practice. Solution n°6 : Dykes water pressure, sloping sides to reduce wave loadings and crest heights sufficient to prevent overtopping by flood waters. They are not intended to preserve beaches. Main environmental requirements & institutional context Dykes are common practices in low-lying coastal areas and are often the cheapest hard defence practice when coastal land is less valuable. Combining with other solutions Dykes aim to be sufficient and stand-alone to protect a stretch of coastline. Assets, advantages and strengths particular to the West African coastal area The sloped seaward edge of a dyke leads to greater wave energy dissipation and reduced wave loadings on the structure compared to vertical structures. This is achieved as the seaward slope forces waves to break as the water becomes shallower. Dyke on Elmina Coast, Ghana. Photo: Hen Mpoano Constraints, weaknesses and difficulties particular to the West African coastal area Category Dykes require high volumes in order to resist Hard engineering solutions [ X ] high water pressures on the seaward face. As a Soft engineering solutions [ ] result, construction uses large volumes of building Coastal planning & risk management techniques [ ] materials, including sand, clay and asphalt, which Compliance with nature-based can be costly. Applying dykes in the shallow slopes requires significant land area and facilitating wave solution criteria energy dissipation results in a large footprint during Yes [ ] construction – all of which are further disadvantages. Maybe, under certain conditions [ ] No [ X ] Substance and Purpose Dykes are designed in such a way that they provide stability under normal and extreme conditions. Structures have a high volume, which helps to resist 39  torm surge barrier/ 3.1.7. S Land claim 3.1.8.  closure dam (or reclamation) General presentation General presentation Storm surge barriers and closure dams are large- Land claim or reclamation is a more aggressive scale coastal defence projects, capable of protecting form of coastal protection, which could be termed tidal inlets, rivers and estuaries from occasional storm as an ‘assault’ or ‘advance the line’ under shoreline surge events (Appelquist et al., 2016) while also management typology. The main objective of land providing a physical barrier, which prevents storm claim is neither erosion nor flood reduction. The aim is surges travelling upstream. Surge barriers help to rather, to create new land from areas previously below keep upstream water levels low, minimising coastal high tide for agricultural or development purposes flooding and can be easily integrated into larger, (Appelquist et al., 2016). However, if land claim is overall flood prevention systems. Such structures designed taking into consideration the potential can be mobile - fixed barriers or gates, which can impact of climate change, measures can be taken to be closed in order to prevent flooding when extreme reduce exposure of these areas to coastal flooding. water levels are forecast (Appelquist et al., 2016). Closure dams are fixed structures that permanently To enclose areas for land claim, hard coastal close off a river mouth or estuary and for these defences must be constructed seaward from the and fixed barriers, water is discharged through, or existing shoreline. Dykes and seawalls are typically pumped over the barrier (IOC, 2009). For appropriate constructed to protect claimed land from sea flooding operation and maintenance, sufficient capacity and (Burgess et al., 2007), and is likely to be accomplished funding resources are required. by enclosing or filling shores or nearshore areas (Bird, 2005). Several terms can also be used when referring Key benefits to land claim including land reclamation, reclamation The two technologies effectively reduce the height of fill and advance the line. This is particularly common extreme water levels behind the barrier when closed, around large coastal cities such as Singapore and and doing so allows for a reduction in the strength Hong Kong, where land values are expensive, thus of existing defences behind the barrier (Hillen et justifying the high costs. In recent years, large-scale al., 2010). Employing these technologies reduces land claims were conducted in Dubai, for residential, construction and maintenance costs for defence on leisure and entertainment purposes including the Isle the landward side of the structures. By reducing the of Palms and the World. height of extreme water levels inside the barrier, the length of a coastal flood defence system may also be Key benefits shortened (Hillen et al. 2010). This would also reduce In future, the main benefit of land reclamation remains maintenance and construction costs for defences on – availability and use of additional land. In terms of the landward side of the barrier. development, coastal land is valued with easy access to land and sea, essential for port development, and Potential collateral effects and highly desirable for housing and leisure facilities. other disadvantages However, with the prospect of rising sea levels, coastal A key disadvantage of storm surge barriers is the defence benefits need to be considered to protect life significant investment required for construction and and infrastructure. maintenance. In addition, mobile barriers also require simultaneous investment in flood warning systems by Potential collateral effects and providing critical data on when barriers need to close. other disadvantages This expenditure can be avoided through the use of The process of land reclamation requires either a closure dam, which allows for lower capital and maintenance costs. Another possible disadvantage enclosure of intertidal habitats by hard defences or of surge barriers and closure dams is the possibility raising the elevation above that of sea level to prevent of flooding on the landward side when river levels are inundation. However, this will lead to a direct loss high and, in the case of mobile barriers, if the defence of intertidal habitats such as saltmarshes, intertidal remains closed for an extended period. flats and sand dunes (French, 1997), affecting many bird and plant species in these zones. Furthermore, West Africa situation coastal squeeze and human development means these areas are largely in decline. Storm surge barrier/closure dams have yet to be considered to protect West Africa coasts. However, Land reclamation can impede littoral sediment flow it is not considered appropriate for the West African and cause erosion in downdrift beaches. The use environment, unless for very specific zones such as of hard defences to reclaim low-lying land can be estuaries bordering large towns. detrimental as these structures cause erosion and 40 shoreline scour. Hard defences also prevent habitat Key benefits adjustment in response to changing factors such as rising sea levels (French, 1997). Cliff stabilization is particularly relevant on exposed and moderately exposed slopes of soft rock (Appelquist et Any type of land reclamation will cause water al., 2016). In most instances, cliff stabilization requires displacement during a natural tidal cycle resulting in a the use of hard structures such as revetments and can smaller area for incoming tides to inundate. The result be categorized as a HES. Nevertheless, the preference is an increase in water depths with intertidal areas for cliff stabilization is to seek the least expensive and submerged for longer causing negative biological most durable method, based on natural processes. In consequences and an increase in the tidal range this sense, it can be seen as a mixed method, making upstream (French 1997). the transition to SES. Land reclamation can also introduce contamination to Collateral effects and other the coastal zone and acidification of coastal waters. This can be problematic if reclaimed land is to be disadvantages used for agriculture or if coastal waters are used for Cliff stabilisation is beneficial for improved public fishing. Contaminants may be introduced through safety, particularly when cliffs are in danger of collapse dredged sediments for elevating land – caused by or landslip. Stabilisation contributes to maintaining the hazardous chemicals from industries located along amenity value, important for recreation and tourism. the coast, from ships or upstream river sources. However, in many cases cliff stabilisation involves Acidification on the other hand, is linked to bacteria hard structures as revetments interferes with natural in estuarine sediments, which creates sulphuric acid coastline dynamics. Cliffs are part of the natural coastal when exposed to air (Anderson, 1991). landscape, a source of sediment for coastal systems and where possible should be untouched, to maintain Work by Linham et al. (2010) on coastal defence unit a carefully balanced sediment budget. Protecting and costs, found that in 2009 the cost of land reclamation stabilising cliffs means sediment input is reduced, by raising elevation in South-East Asia varied from however this can lead to negative effects downdrift, US$3-5 per cubic metre of material used. Land and not feasible in densely populated areas. reclamation in Hong Kong Harbour in 2009, (Yim, 1995) put the cost per square metre of reclaimed land The cost of cliff stabilisation depends on local at US$3.9 when utilising marine fill and US$6.4 when conditions and individual situations, and likely to using land-based fill material. be associated with revetment construction, while channelling runoff into covered or paved drains While these costs may be representative of South- also involves costs. Alternative and low technology East Asia, global unit costs for land reclamation are approaches such as dumping tree branches etc. over not widely available. the cliff edge is seen as a poor solution. Dumping does not prevent the risk of sliding and is more likely West Africa situation to destroy vegetation cover while increasing erosion Land reclamation is not well developed in West as a result. Africa, partly due to its high costs of implementation. Smoothing and regrading slopes leads to land loss, However, this approach was applied in the Keta for example if a cliff toe is moved seaward and the project in Ghana and in the Eko Atlantic City project in cliff top landward in an attempt to reduce unstable Nigeria where a new planned city is being constructed slopes, this can result in a loss of valuable beach front on land reclaimed from the Atlantic Ocean. and cliff top areas. The loss of land may be opposed by local stakeholders if the benefits of stabilisation are 3.1.9. Cliff stabilisation not made clear by early and thorough consultation. General presentation West Africa situation Cliff stabilisation relates to measures carried out West Africa’ coastline is diverse and extensive because to minimise the erosion of sloping soft rock coasts of its broad sandy beaches, dense mangrove forests where landforms are susceptible to erosion. With and rocky cliffs. Considering costs and the inadequate an ultimate goal to stabilise coastlines’ vulnerable to less expensive alternatives mentioned above, cliff erosive forces such as waves, winds, tides, nearshore stabilisation along the West African coastline should currents, storms and rising sea levels due to relatively be considered as a prudent coastal management non-compacted sediment. practice in specific areas of the coast, such as the Cap Blanc (Nouadhibou), the tip of the Cap Vert peninsula (Dakar) or rocky promontories in Ghana. 41 42 Hard-engineering solutions 1. Breakwater 2. Groynes  eawall preventing flooding 3. S event  hrinking beaches due to lack 4. S of sediment supply 5. Accretion 6. River embankment  etty to prevent silting of the 7. J estuary 8. Water-controlled irrigated agriculture replaces flood agriculture and mangroves Cliff stabilisation 9.  6 3 1 2 8 4 5 7 9 Illustration by Laurent Corsini Ghana. Photo: Hen Mpoano 43 Solution n°7 : Cliff stabilisation Category Hard engineering solutions [ X ] Soft engineering solutions [ ] Coastal planning & risk management techniques [ ] Compliance with nature-based solution criteria Yes [ ] Maybe, under certain conditions [ X ] No [ ] Substance and Purpose Cliff stabilisation relates to measures carried out to minimise erosion of sloping soft rocky coasts. These Cliff stabilisation in Gorée Island, Senegal. landforms are susceptible to erosion due to relatively Photo: Madjiguene Seck/ World Bank non-compacted sediments which are particularly Combining with other solutions vulnerable to erosive forces such as waves, winds, tides, nearshore currents, storms and rising sea Revetments may be used to protect certain fragile levels. The ultimate goal is to stabilise the coastline. parts of the cliff and to channel runoff water into covered or paved drains. Main environmental requirements & institutional context Assets, advantages and difficulties particular to the West African coastal area The cost of cliff stabilisation depends on local conditions, individual situations and likely to be A stabilised shoreline with the landscape preserved associated with revetment construction. The almost in its original form. preference for cliff stabilisation is to seek the least Constraints, weaknesses and issues particular expensive and most durable method, based on to the West African coastal area natural processes. Stabilisation interferes with natural coastal dynamics where smoothing and slope re-grading causes land loss and may cause erosion in the long run. SOFT ENGINEERING 3.2.  shape of a beach affects its potency to attenuate wave energy. For example, a wide and shallow beach SOLUTIONS dissipates a considerable amount of wave energy, while a steep and narrow beach reflects incoming 3.2.1. Beach nourishment wave energy seawards. General presentation While beach nourishment was used in many hundreds Beaches occur where there is sufficient sediment for of locations under a wide variety of environmental wave deposition above water level along lakes, open conditions (e.g., Psuty and Moreira, 1990; Silvester ocean coasts, embankments and estuaries (Finkl and and Hsu, 1993), and frequently integrated with HES Walker, 2005). Beach nourishment is a SES approach as part of strategic shore protection efforts, there is to coastal protection which involves the artificial much debate about whether the procedure is the best addition of suitable quality sediment for a beach area solution to tackle the challenges of coastline retreat. with a sediment deficit (Finkl and Walker, 2005; Linham Although there are many arguments against beach and Nicholls, 2010). In other words, nourishment nourishment, artificial supply of beach-sand remains involves beach recharge, beach fill, replenishment, re- the most practical method of protection against nourishment and beach feeding. coastal flooding from storm surges, advancing the shoreline seaward, and widening recreational beaches Key benefits (Finkl and Walker, 2005). Beach nourishment is employed to rebuild and West Africa case studies maintain a sandy beach at a width which provides storm protection and is of great importance because Beach nourishment is practiced along few coastlines of its ability to accentuate wave energy dissipation. in West Africa, for example, on the bar beach of The interaction of waves differs with respect to beach Victoria Island in Lagos, Nigeria, the beaches of profile shapes and gradient where the cross-sectional Kololi in Gambia, and the touristic beaches of Saly in 44 Senegal. Victoria Island’s bar beach is located east rapidly eroding beach. Other nourishment projects of the eastern pier, downdrift of the natural mouth of were conducted in Gambia on the Banjul and Kololi Lagos Port (Awosika et al., 1993; Folorunsho, 2004; beaches (UNESCO-IOC, 2012). Despite efforts, the UNESCO-IOC, 2012). To avoid the impending collapse Banjul beach eroded 68 m in 7 years and 134 m of commercial and residential buildings, federal at Kololi bar sea-view point where the government and state offices and disruption of socio-economic invested US$20 million to artificially nourish a stretch activities on Victoria Island, artificial nourishment of beach 100 m wide in Kololi (Bromfield, 2006; formula was used until a more permanent solution UNESCO-IOC, 2012). Gambia opted for this soft was found. The beach was scheduled to be artificially technique to preserve the aesthetic integrity of the replenished at 2 - 3-year intervals, making it a costly beach. It was observed that this option resulted in option in the long term but it ultimately failed because a loss of half of the imported sand over two years it required continuous nourishment to stabilise the (Bromfield, 2006; UNESCO-IOC, 2012). Solution n°8 : Beach nourishment Beach nourishment in Saly, Senegal. Photo: Senegal World Bank Combining with other solutions funded Tourism Project (PDTE) Can be used as a solution stand-alone or integrated Category with hard structures as part of strategic shore Hard engineering solutions [ ] protection efforts. More specifically, it can be used Soft engineering solutions [ X ] to compensate the drawback effects of groynes Coastal planning & risk management techniques [ ] including sediment starvation and downdrift erosion. Compliance with nature-based Assets, advantages and strengths particular to solution criteria the West African coastal area Yes [ ] The result of beach nourishment is to keep the Maybe, under certain conditions [ X ] sandy beach at a width that provides protection from No [ ] storms. Beach nourishment enhances the dissipation of wave energy through its ability to maintain or Substance and Purpose reshape the beach profile. A wide, flat beach Beach nourishment is a coastal protection approach dissipates a considerable amount of wave energy which involves the artificial addition of sediment while a narrow, steep beach reflects incoming wave of suitable quality for beaches with sediment energy, resulting in increased erosion. deficit. Nourishment involves beach recharge, fill, Constraints, weaknesses and difficulties replenishment, re- nourishment and feeding. particular to the West African coastal area The beneficial effect of beach feeding is temporary, Main environmental requirements so it should be repeated every two or three years, & institutional context making this solution a costly option in the long Availability of mined gravel or sand; availability term. The mining of gravel or sand may cause some of a specially equipped boat or powerful trucks environmental damages. with spears; availability of funds over a long period of time. 45  une construction/ 3.2.2. D West Africa case study rehabilitation The only sample cases of dune rehabilitation in West Africa come from Nouakchott and Diawling in General presentation Mauritania and Saint Louis in Senegal. In Nouakchott Dune rehabilitation is the restoration of natural or a project for Rehabilitation and Extension of the Green artificially impaired dunes, to gain the greatest coastal Belt at Nouakchott began in 2000 and was completed protection benefits. Naturally occurring sand dunes in 2007. Previously between 1987 and 1992, 800 are wind-formed sand deposits produced through a hundred ha of stabilised and fixed continental dunes store of sediment in a zone landward of normal high were completed to enhance reforestation. The project tides, while artificial dunes are engineered structures in Mauritania led to the successful stabilisation of 50 created to mimic functioning natural dunes. Artificial ha of dune ridge in Nouakchott (the area between the dune construction and rehabilitation technologies aim wharf and the fish market), with sand trapping and to reduce coastal erosion and flooding in adjacent reforestation (UNESCO-IOC, 2012). Fixed costs to coastal lowlands. A simple artificial dune construction mechanically stabilise and biologically remedy about involves placing sediment from dredged sources on 600 linear metres of dunes amounted to US$4,184. the beach and reshaped into dunes using bulldozers With one linear meter of mechanical stabilisation or other possible means. estimated at US$6.97. Solution n°9 : Dune construction/rehabilitation Category Hard engineering solutions [ ] Soft engineering solutions [ X ] Coastal planning & risk management techniques [ ] Compliance with nature-based solution criteria Yes [ X ] Maybe, under certain conditions [ ] No [ ] Substance and Purpose Dune rehabilitation is the restoration of natural or artificial impaired dunes, to gain the greatest coastal protection benefits. Naturally occurring sand dunes are wind-formed sand deposits produced through a sediment store in the zone just landward of normal high tides. Artificial dunes are engineered structures created to mimic the functioning of natural dunes whose construction and rehabilitation are aimed at reducing coastal erosion and flooding in adjacent coastal lowlands. Main environmental requirements Dune Rehabilitation in Mauritania. Photo: Modestine Victoire Bessan/IUCN & institutional context One linear meter of mechanical dune stabilisation is Assets, advantages and strengths particular to up to US$6.97 (estimate from Nouakchott project, the West African coastal area 2000 to 2007). The beauty of the landscape is preserved or Combining with other solutions enhanced. Dune rehabilitation is often accompanied by a planting and reforestation, for longer lasting dunes. Constraints, weaknesses and difficulties particular to the West African coastal area Dunes occupy a lot of land and generally unsuitable for frequent human or herd visits. 46 Senegal. Photo: AMP de Saint Louis  etlands and mangroves 3.2.3. W US$82 billion (Summary report, May 2018, The Nature Conservancy, IH Cantabria and Bundnis Entwicklung restoration Hilft). Estimated costs in 2012, based on examples in West Africa, including logistics for collecting General presentation propagules and catering to villagers reveals that a Wetlands refers to a diverse range of shallow day of reforestation mobilising and catering for 100 water and intertidal habitats that occur in various people is estimated between US$333 and US$450 locations around the world. Wetland restoration is the (UNESCO-IOC, 2012). rehabilitation of impaired wetlands. West Africa case studies Key benefits In West Africa, mangrove forests cover large areas, for Mangrove forests are the best-known variety of instance Ghana’s 550 km of coastline includes more coastal wetland and contribute to wave attenuation than 100 estuaries and lagoons (coastal wetlands), via sediment trapping (Koch et al. 2009) along with but these valuable natural resources are under threat other coastal biotic structures, such as coral reefs due to human and natural impacts. The West African and seagrass beds. Plants attenuate currents and mangrove forest includes six species of trees, the waves, depositing sediment particles and as a result, most common of which are the Rhizophora (the red vegetated areas become shallower over time, further mangrove) and the Avicennia (the white mangrove). contributing to wave attenuation. In very dense mangrove forests, full attenuation of wind-induced Mangrove forests have been the subject of waves may occur within 30 m of the edge, while in rehabilitation projects in West Africa for some time. low-density mangroves, much wider vegetated areas In 2008, an area of 1.5 ha was replanted with are required to obtain the same results. Rhizophora (UNESCO-IOC, 2012) on the Island of Djirnda in Saloum, Senegal. Reforestation was also A recent study on the global value of mangroves for conducted in Senegal in Gagué Sharif, Sine Saloum, risk reduction and climate adaptation revealed that and Casamance. However, mortality was high, and mangroves reduce annual flooding for more than 18 growth slowed due to high soil salinity. The inexpensive million people. Without mangroves, flood damages cost of restoration can be instrumental in motivating would increase by more than 16 per cent at a cost of 47 people to pursue restoration projects, however areas re-established by maintaining the existing coastline to be replanted must be chosen carefully so as not position with vegetative transplants from healthy to prejudice customary land tenure and traditional marshes. Wetlands restoration and recreation can activities (Cormier-Salem and Panfili, 2016). also reduce or even reverse wetland loss as a result of coastal development. Coastal wetlands provide a Further options for wetlands number of important ecosystem services including restoration water quality and climate regulation, considered valuable accumulation sites for sediment, carbon and Salt marshes are another useful variety of coastal nutrients, also providing vital breeding and nursery wetlands that require careful consideration and often grounds for a variety of birds, fish and mammals. used in rehabilitation projects through managed realignment schemes by moving back the existing line of defence. Additionally, salt marshes can be Solution n°10 : Wetlands and mangroves restoration Category Hard engineering solutions [ ] Soft engineering solutions [ X ] Coastal planning & risk management techniques [ ] Compliance with nature-based solution criteria Yes [ X ] Maybe, under certain conditions [ ] No [ ] Substance and Purpose Wetland restoration is the rehabilitation of previously existing impaired wetland. The term wetland refers to a diverse range of shallow water and intertidal habitats. One well- known type of coastal wetland is the mangrove forest. Mangroves contribute to wave attenuation via sediment trapping. As currents and waves are attenuated by plants, sediment particles may be deposited. Main environmental requirements & institutional context Requires modest funds but importantly requires community approval and participation to avoid wood harvesting. Mangrove restoration in Benin. Photo: Corde ONG Combining with other solutions Wetlands and mangrove restauration systems aim to be sufficient and stand-alone to protect a stretch Assets, advantages and strengths particular to of coastline, more specifically in estuarine areas and muddy coasts. the West African coastal area The landscape’s beauty and the biodiversity are preserved. Ecosystem functions are maintained with soil stability, climate regulation, and improved water quality. Constraints, weaknesses and difficulties particular to the West African coastal area The choice of areas to be replanted must be carefully chosen to ensure usual land tenure and traditional activities are unaffected. 48  luvial sediment 3.2.4. F and downstream coastline. Construction should be encouraged for modern dams with sluicing designs management to improve sediment through-flow, allowing continued sediment deposits in delta areas to minimise General presentation subsidence (Appelquist et al., 2016). Fluvial sediment management is a holistic method to move sediment supply from rivers to coast, taking into Key benefits account the full range of human activities at river basin Appelquist et al. (2016) signifies the advantages level (Appelquist et al., 2016). of implementing a fluvial sediment management Human activities can increase and reduce the fluvial scheme including minimising coastal erosion and sediment supply to the coast. The key drivers of land subsidence. As fluvial sediment is vital for increased sediment load include land clearance sediment balance, it is important at sedimentary for agriculture and other land surface disturbances coastlines to maintain stability and essential for delta such as forest clearance, logging and mining. These areas. In many areas, fluvial sediment supply is also activities can damage sensitive coastal habitats very important for maintaining ground elevations unable to cope with high levels of sedimentation, to combat compacted relatively young, and weak for example coral reefs. The key drivers of reduced sediments. The significance of fluvial sediment supply sediment supply include soil conservation and, most becomes evident when considering its importance in importantly, where dams and reservoirs trap sediment maintaining fertile land, often located in delta areas, (Walling 2006). In many large river basins, several for agricultural purposes. By addressing sediment drivers are present and prove a complex exercise to entrapment behind dams, it becomes possible to determine the impact of human activities. However, a increase longevity of such structures in the face of reduction in fluvial sediment supply is a greater and upstream sedimentation. If sediment through-flow more pressing matter for coastal inundation, erosion measures can be incorporated in such structures, and flooding. it clearly offers a win-win scenario for people who develop dams and coastal communities. Over the past decades a large number of the world’s rivers experienced a dramatic decrease in sediment Potential collateral effects and supply to the coast due to human activities (Ly 1980; Walling 2006). Since 1950 the number of dams other disadvantages increased more than sevenfold globally, and over The main disadvantage of fluvial sediment 40 per cent of global river discharge is currently management relates to resources required to intercepted by large reservoirs. In many rivers, sand determine the sediment flows at basin level and extraction for construction and civil engineering balance differing social interests. River damming can purposes is a significant cause in the decrease of provide great benefits to society through hydropower sediment transport to sea (Padmalal et al. 2008), production, agricultural irrigation, flood and drought consequently downstream coastal areas often suffer control, but at the same time pose major impacts major sediment deficits. on coastal areas downstream and can be used as a political issue to prioritise different goals. Moreover, it Advanced modelling systems offer possibilities for requires highly specialised expertise and collaboration calculating reliable estimates of coastal sediment between a range of different institutions at river basin supply (DHI, 2015). While there is no standard level. In some cases, this can involve cross-border approach for fluvial sediment management, a clear coordination and can be a complex and sensitive understanding of the factors affecting coastal exercise. In some locations, institutions are already sediment supply for a river basin is a key requirement established to deal with river basin management and (Appelquist et al., 2016). In some larger coastal areas in these cases coastal managers frequently work land subsidence is due to decreasing fluvial sediment directly with institutions. and excessive underground water extraction. Geological sediment compaction can have much The complexity of fluvial sediment management greater impact than the global rise in sea levels and denotes that it requires significant scientific and awareness of this coastal management component administrative resources and, in many cases, is vitally important (Milliman and Mei-e 1995). Often coordination at political level. Coastal managers may coastal areas suffer from earlier river management need to find an appropriate balance between engaging decisions which are difficult to reverse and require in activities at river basin level and implementing various damage control measures such as HES local management actions. As river basins are large or beach nourishment to rectify. However, fluvial geographical features, effective fluvial sediment sediment management should be taken into account management is likely to require the cooperation of in all new management decisions at river basin level, neighbouring cities, states, provinces or countries with encompassing a holistic view of the whole river basin different objectives and priorities. Without cooperation 49 between users, effective management of the resource sands originating from the north (Mauritania) and is likely to be challenging. transported by a strong littoral drift (Barusseau, 1980). The interaction between fluvial and marine induced The costs and financial requirements of fluvial sediment sedimentary regimes is of primary importance for management is highly dependent on the scope the spit’s evolution and natural changes in coastal and scale of the activity and the human resources dynamics revealed the sensitive nature of the mouth and equipment requirements for its implementation and nearby coastal region to any change in the (Appelquist et al., 2016). sedimentological and hydrological regime of the Senegal River (Barusseau et al., 1998). Therefore, West Africa case study the construction of hydraulic infrastructures such as For these reasons, the management of sedimentary the Manantali and Diama Dams greatly modified the flows has yet to become operational in West Africa. hydrological conditions in the middle delta and estuary The two cases presented below, in Ghana and (Dumas et al., 2010). Senegal respectively, show that sedimentary issues are of major importance in certain areas. The case of The Senegal River contributes a terrigenous input, Saint-Louis, at the mouth of the Senegal River, shows mainly as a suspension load during floods, but this the magnitude of the challenges to be overcome to suspended matter has no influence on the littoral implement sedimentary management. sedimentary budget of the Senegal Delta wave- dominated coast (Barusseau et al., 1998). Although In Ghana, the construction of the Akosombo Dam sand input played a significant role in the delta’s resulted in a reduction of sediment supply to the coast construction by feeding successive Holocene beach by about 90 per cent. It then became necessary to barriers (Monteillet, 1986), later observations show undertake a US$83 million coastal protection project that the current sediment transport is less dependent to stabilise the coastline of Keta (Ly 1980; Boateng et on the fluvial contribution. The sediments’ textural al., 2011) in the early 2000s. compositions on both sides of the beach barrier indicate that the marine sand input, through littoral Since the late 1980s, the Senegal River valley, drift moving north to south, is the main contribution located in Mali, Senegal and Mauritania has become to the Langue de Barbarie spit construction. In this more artificially engineered with the building of respect, there is no strong modification in a post- embankments, free-flow canals, irrigation ditches and dam context (Barusseau et al., 1998).However, the sluice gates (Dumas et al., 2010). These hydraulic outer estuary region’s hydrodynamic system greatly structures were developed alongside the construction changed, which was demonstrated by the banks’ of two larger structures, the Manantali Dam, located morphological reworking. Major transformations upriver in Mali, and the Diama Dam, the first to be resulted from dominating marine factors, greatly completed in 1986, near the mouth of the river at diminishing fluvial influence. Saint-Louis (Figure 3). Figure 3 - The Senegal river basin and its new mouth. (Dumas et al., 2010) The Senegalese coast north along the river mouth is prone to erosion to the north and the shoreface’s The lower stretch of the Senegal River is diverted deeper areas, while accumulation is prominent southward by a sand spit 30 km long (The Langue towards the south. As a result, forcing induced by de Barbarie or Barbary Spit), where the town of estuarine behaviour in the lower stretch of the Senegal Saint-Louis is located. The spit was mainly built by River, down current from the Diama Dam, caused 50 considerable disruption of the river mouth topography expected along major streams where people and and coastline equilibrium. The marine factors were property are not threatened. They may also be reinforced, denoting lengthening of the Langue de issued as an update to previous warnings and Barbarie beach barrier, narrowing the river mouth watch alerts. and the accumulation of mouth bars (Barusseau et An effective flood warning system requires local al., 1998). rainfall, stream level, and streamflow regular data Coastal erosion in Saint-Louis and actions to tackle collection, which requires routine monitoring, at the dams’ effects on coastal sediment supply, are yet stream gauges and precipitation measuring sites. A to be implemented. real-time monitoring system with telemetry facilities enables easier data collection and in many cases is more cost-effective while also allowing for a most rapid COASTAL PLANNING 3.3.  response to a flood event. Developing a flood warning AND RISK MANAGEMENT system requires three basic factors - data collection via gauging, data processing, the appropriate TECHNIQUES hardware and software, and flood warning information Coastal planning and risk management techniques dissemination. are terms used to encompass a wide range of miscellaneous methods, sharing a common objective The most effective flood warning methods extend to mitigate coastal hazards. These methods involve beyond the installation of gauges and telemetry reinforcement of monitoring capacity, creating new equipment and should include the recruitment of rules and policies, the production and dissemination qualified staff and carefully designed procedures to of information, and the promotion of safer and provide early warning. appropriate behaviour. While these methods are light In communities with no flood warning program, further in terms of building concrete structures, they are guidance and technical support, as well as outreach intensive in terms of monitoring systems, studies, and education, and community leadership should communication, development of new response be provided to interested communities. Setting up strategies, institution strengthening and improvement appropriate flood warning systems can provide critical in the protection and management of infrastructures. information to protect property and save lives, even for communities less prone to flooding.  lood early warning 3.3.1. F Early warning technologies are relatively low-cost and systems successfully employed in a diverse range of territories General presentation from a developed country such as the USA, to a developing country such as Bangladesh (IOC, 2009). An early warning system is a way of detecting threatening events in advance, enabling simultaneous This guide offers instruction for individuals, public warning so that actions can be taken to reduce communities, and organizations interested in the event’s adverse effects (Appelquist et al., 2016). establishing and operating flood warning systems. In West African coastal areas, flood events should be considered a priority where a flood warning system West African case study can reduce exposure to coastal flooding through Planning for flood warning is straightforward and promoting effective temporary evacuation. feasible and can be implemented in West Africa to minimise loss of life and injury when coastal Benefits and attention points disasters occur. In West African coastal cities, early Flood alert warnings are issued on a community warning schemes are yet to be effective as flood basis, or for particular coastal areas. More severe damage reduction measures. There are plans to put flood warnings are issued if widespread flooding in schemes in Cotonou and Dakar but schemes in is expected across a large region, or if flooding is place in Accra and Lagos did not meet expectations imminent or actively taking place. These alerts include when 200 people lost their lives after the June 2015 several basic categories: flood in Accra (IFRC, 2015) and the 2012 flood •  flood watch is issued when conditions suggest A in Lagos (IFRC, 2012). Many of the early warning the possibility of flooding, or if flooding is systems developed in West African countries were anticipated within 12 - 48 hours. implemented under projects funded by bilateral agencies such as the United Nations Development •  flash flood watch and warnings follow the same A Program, the World Meteorological Office etc., but protocol, but indicates potential for especially when poor maintenance is practiced, unfortunately, rapid flooding, usually from heavy rain or dam many systems fail. failure. • Flood statements are issued when flooding is  51 Solution n°11 : Flood early warning systems Category Combining with other solutions Hard engineering solutions [ ] Flood early warning systems can be combined Soft engineering solutions [ ] with any other coastal defence solution, effective in Coastal planning and risk management complementing flood risk mapping. techniques [ X ] Assets, advantages and strengths particular to Compliance with nature-based solution criteria the West African coastal area Yes [ X ] This planning approach is straightforward and Maybe, under certain conditions [ ] feasible and its implementation in West Africa will No [ ] minimize fatalities. Substance and Purpose Constraints, weaknesses and difficulties particular to the West African coastal area An early warning system is a way of detecting threatening events in advance. This enables public For effective rollout of early warning systems, warnings to be issued at the same time so actions can communities require training as well as permanent and be taken to reduce the adverse effects of an event. rigorous monitoring of meteo-oceanic phenomena by This type of hazard needs to be considered as a dedicated services. priority in West African coastal areas where the primary objective is to reduce exposure to coastal flooding through promoting effective temporary evacuation. Main environmental requirements & institutional context Early warning technologies are relatively low-cost, requiring regular collection of local rainfall, stream level, and streamflow data, achieved through routine monitoring.  lood regulation through 3.3.2. F The Manantali Dam controls just part of the river basin, so when Saint-Louis was flooded in September hydraulic structures 2003, the dams couldn’t prevent or control flooding. operations The effects of the first flood were amplified when a second flood wave was observed at the same time General presentation up-river at Bakel and was expected to reach the In estuarines areas where flooding risk is mainly city 20 days later. Measures to protect Saint-Louis, dependent on river flow, regulation infrastructures located approximately 30 km from the river mouth and (dams) should be integrated in the hydrological separated from the ocean by the Langue de Barbarie management model for flooding risk reduction. Dams coastal spit, were put in place. As an emergency and sluice gates enable regulation of river water flow response an artificial opening in the Barbary Spit was and water management depends extensively on dug, 7 km down-river from Saint-Louis to enable river human decisions. water to drain and shorten the distance between the town and river mouth. The result was an immediate West Africa case study reduction in flood water, but this subsequently resulted in unforeseen and adverse environmental impacts Management of the Senegal River caused issues in including widening of the breach, increased erosion, the Saint-Louis city area (Dumas et al., 2010) where and villagers who lost their homes became displaced. priorities for the two dams were predominantly geared towards developing irrigated crops in the former flood This tragic and unexpected event illustrates that dams plains and electricity production in the Manantali Dam. set up and operated along West African rivers were River authorities tended to maintain high water levels not designed for flood regulation. in the Manantali Reservoir for as long as possible, but this was incompatible with a management scheme aimed at controlling floods down river from Diama. 52 3.3.3. Groundwater management Despite these worrying concerns, groundwater management is yet to be applied in West Africa. General presentation Groundwater management refers to a range of Risk mapping, flood risk 3.3.4.  measures to ensure sustainable groundwater availability, limit saltwater intrusion and land mapping subsidence. Related activities include appropriate General presentation surface water management, flood management and Risk mapping is an exercise to define coastal areas alternative water supplies (Appelquist et al., 2016). A at risk under extreme conditions or accident. Coastal primary issue in coastal areas is saltwater intrusion into zones are home to human habitats, industrial, tourist, fresh groundwater reserves, which has the potential to agricultural and/or ecological environments. The decrease freshwater storage in coastal aquifers and value of these environments, combined with a high in extreme cases, results in abandonment of supply exposure to marine hazards such as flooding, oil spill wells. events etc, leave coastal zones high-risk areas, hence the mapping objective is to reduce the human and Benefits and attention points economic impact of such coastal events. Groundwater management encompasses monitoring and assessment of groundwater conditions and Flood risk identification and mapping requires focus direct management interventions where proactive to plan a more effective emergency response to this management produces a wealth of benefits. Primarily, type of hazard (Appelquist et al., 2016), considered this approach helps to ensure sustainable groundwater frequent and widespread on West African coasts. supply for essential human needs. Persuading Flood mapping is designed to increase awareness of planning authorities to consider long term supply flooding among the public, local authorities and other issues will help maintain supply consistency over a organisations. wide range of climate scenarios. Careful monitoring of Geographic information systems (GIS) are frequently groundwater supplies helps ensure consistency and used to produce flood maps and provide an effective supply quality, while taking hydrological changes into way of assembling information from different maps account in due course. and digital elevation models (Sanyal and Lu 2003). Groundwater management is generally viewed as Using GIS, the extent of flooding can be calculated by a positive and proactive measure with few direct comparing local elevations with extreme water levels. disadvantages. However, fully implementing and More advanced and accurate flood maps are likely to enforcing such strategies requires an allocation of be based on complex numerical models because of the significant dedicated human and financial resources. lack of data for extreme events where implementation Plans should encompass all national plans and requires a degree of expertise. It should be noted that integrated into water resources management to the collection of topographic and bathymetric data to identify actions for an effective framework. supplement information for water levels and extreme wave heights would be more costly. West Africa context By combining layers of data on flood probabilities (flood Preliminary samples of groundwater from coastal wells mapping) with layers of data on human, economic along the Dzita coastline in Ghana indicate significant and natural issues, GIS enables the production of saltwater intrusion, contaminating water for human flood risk maps. For example, maps can guide new consumption and agriculture. Samples indicates that investments outside high-risk areas, will reduce future saltwater is pushing inland, mixing and progressively flood risks and promote sustainable development, replacing fresh groundwater. The result is due to a where integration should be considered in coastal reduction in nearshore groundwater levels and likely planning procedures. as an outcome of over-pumping fresh groundwater for irrigation purposes within the coastal community. Benefits and attention points The same phenomenon has been observed for In itself, flood risk mapping does not cause a several years on the Petite Côte of Senegal, in the reduction in flood risk. It must be integrated into other tourist region south of Dakar. procedures, such as town planning and emergency response planning, before full benefits can be realised. 53 54 Soft-engineering, coastal planning and risk management solutions  ourishment of the beach to 1. N give it back its natural shape  une restoration through the 2. D plantation of trees  he beach regains its width 3. T through the normal supply of sediment  atural flooding in estuarine 4. N areas allows the traditional rice-crop system and the rehabilitation of the wetlands and mangroves  flood early warning system 5. A using satellites allows people to leave the agricultural camp in time in case of flooding  etback and relocation to 6. S prevent the danger of building damage and collapses 5 1 2 4 3 6 Illustration by Laurent Corsini Benin. Photo: Corde ONG 55 West African case study 3.3.5. Coastal setbacks In West Africa, most countries are extremely General presentation vulnerable to the impact of flood hazards as a result of limited investment in infrastructure (Ntajal et al., 2017), Coastal setbacks are a prescribed distance to a coastal tall building vulnerability, settlements in flood zones, feature such as the line of permanent vegetation, economic dependence on agriculture and poorly within which all or certain types of development are resourced institutions. Flood mapping is an important prohibited (Cambers, 1998). A setback may dictate a process for sub-Saharan countries with suitable minimum distance from the shoreline for infrastructure variations for each country. Every year the Government or new buildings or may require a minimum elevation of Togo, employ the services of institutions such as above sea level for development. Two types of setback the Ministry of Environment, the Ministry of Territorial are identified - elevation setbacks to deal with flooding Administration, the Ministry of Civil Protection, the Red and lateral setbacks to deal with erosion (Appelquist Cross and others (Ntajal et al., 2017), in flood mapping et al., 2016) where a setback area provides a buffer to save lives and properties at the downstream end between a hazard area and coastal development of the Mono River. Assessing and mapping of social (Fenster, 2005). The idea is that properties under flood risk in the Lower Mono River Basin, revealed consideration should be located sufficiently set back that all communities were exposed to flood risk and in from the average high-water mark to be unaffected particular Agbanakin, Azime Dossou and Togbavi with by the sea despite a foreseeable increase in the high- high flood risk levels. water mark (assuming a given rising sea-level rate scenario). The actions of international organisations and civil society leaders to initiate programmes that prevent Setback distances are determined either as (1) a or mitigate flooding are not seen by communities in fixed setback which prohibits development of a fixed West Africa. Flood-prone regions in other areas of reference feature for a fixed distance landward; or West Africa need to be surveyed and mapped more (2) a floating setback which uses dynamic, natural adequately and systematically for a more effective phenomenon to determine setback lines and can disaster risk reduction and climate change adaptation. change according to an area’s topography or shoreline movement measurements (Fenster, 2005). Ideally, setbacks are established based on historic erosion rates or extreme water levels rather than adopting arbitrary distances which do not truly represent the threat from erosion or coastal flooding (Appelquist et al., 2016). Solution n°12 : Risk mapping, flood risk mapping Category Main environmental requirements Hard engineering solutions [ ] & institutional context Soft engineering solutions [ ] Advanced and accurate flood maps are based Coastal planning and risk management on complex numerical models. However a lack of techniques [ X ] observed/field data on extreme events requires the use of numerical modelling to forecast possible outcomes, Compliance with nature-based solution criteria with inputs from qualified experts for implementation. Yes [ X ] Maybe, under certain conditions [ ] Combining with other solutions No [ ] Flood risk mapping can be combined with any coastal defence solution. It is particularly useful for Substance and Purpose flood early warning systems and plays a central role in Flood mapping is designed to increase awareness all planning activities. of the likelihood of flooding among the public, local authorities and other organisations. By combining Assets, advantages, and strengths particular to data on flood probabilities (flood mapping) with data the West African coastal area on human, economic and natural issues, GIS enables Risk and flood mapping is an essential tool for effective the production of flood risk maps, which should be integrated coastal zone management. integrated into coastal planning procedures. Constraints, weaknesses and difficulties particular to the West African coastal area This exercise is costly in terms of data requirement and expert time. 56 Setbacks provide protection to properties against It is important to emphasise that establishing coastal flooding and erosion, ensuring that buildings setbacks does not guarantee the coast in question are not located in an area susceptible to hazards. The will be shielded from strong storms and associated approach allows erosion to continue along strategic coastal flooding and erosion (Healy and Dean, 2000). sections of the coast while further development As with all coastal adaptation measures, residual risk is restricted. This allows eroded sediment to be will remain, meaning that the protected areas are still transported to areas along the shore, thus enhancing subject to some risk in the case of an event. Setback the level of protection afforded by helping to maintain policies only serve to prolong the lifetime of structures wide, natural beaches. By managing the coast in built on the shoreline. With continued shoreline this natural state, adjustments by the coastline to erosion or rising sea levels, another shoreline policy changing conditions such as rising sea levels can be will eventually be required if these structures are to be made without property loss (Kay, 1990). preserved. More cautious measures can be taken to reduce residual risk, which may include the adaptation Benefits and attention points of other management approaches. Setbacks provide a highly effective method of minimising property damage from coastal flooding West Africa context and erosion, by removing structures from the hazard On densely populated stretches of coastline with zone. They provide a low-cost alternative to shoreline tourist settlements, there are already regulations to erosion or flood protection works such as seawalls prohibit building close to the sea within a limit defined or dykes, which have their own disadvantages. Unlike by the highest waves at the highest tides (the case of hard structures, setbacks help to maintain the natural Grand Bassam in Côte d'Ivoire). appearance of the coastline and preserve natural shoreline dynamics. Setbacks also help to maintain Regretfully the coastal setback approach is not yet shoreline access by preventing development on the sufficiently used as a management option for the West immediate seafront, as well as providing open space African sub-region, mostly likely because it does not fit for communities to enjoy the natural shoreline. with the spontaneous colonisation pattern of coastal regions. Colonisation and new habitat construction Over time, rising sea levels will reduce the size of the on the coast often take place outside any legal buffer zone between structures and the sea. As a framework, but this de facto situation should change result, setbacks will need to be periodically reviewed in future, in the interest of the communities who live to ensure that buffer zones continue to provide and earn a living along the coast. sufficient protection. Solution n°13 : Coastal setbacks Main environmental requirements Category & institutional context Hard engineering solutions [ ] The communities’ understanding and compliance to Soft engineering solutions [ ] agree not to build inside the prohibited zone. Coastal planning and risk management Combining with other solutions techniques [ X ] Coastal setback can be combined with any coastal Compliance with nature-based solution criteria defence solution. Good complementarity with flood risk Yes [ X ] mapping and coastal zoning. Maybe, under certain conditions [ ] Assets, advantages and strengths particular to No [ ] the West African coastal area Substance and Purpose Setbacks provide a highly effective method of Coastal setbacks are a prescribed distance to minimising property damage due to coastal flooding a coastal feature such as the line of permanent and erosion, by removing structures from the hazard vegetation, within which all or certain types of zone. They help to maintain the natural appearance of development are prohibited. A setback may dictate a the coastline and preserve natural shoreline dynamics. minimum distance from the shoreline for new buildings Setbacks also help to maintain shoreline access by or infrastructure facilities or may state a minimum preventing development immediately on the seafront. elevation above sea level for development. The setback area provides a buffer between a hazard area and Constraints, weaknesses and difficulties coastal development. particular to the West African coastal area Does not fit with the spontaneous colonisation pattern of coastal regions. 57 3.3.6. Managed realignment Flood proofing and 3.3.7.  General presentation sheltering Managed realignment commonly includes setting General presentation back the line of an actively maintained coastal defence The objective of flood proofing is to minimise flood to a new line, landward of the original or preferably, impacts on coastal structures (Appelquist et al. 2016). to elevated ground. This will augment the creation of This includes raising structures above floodplains, an intertidal habitat between old and new defences. using plans and construction materials more resistant Managed realignment is therefore the deliberate to flood damage, which can prevent flood waters from process of changing flood defences to allow flooding entering structures on potential flood zones. of an already defended area (Leggett et al. 2004). A number of terms may be used as an alternative to Flood shelters are elevated and robust structures managed realignment. can provide shelter to local residents during extreme weather events. Such structures are complemented Benefits and attention points by flood forecasting and warning systems to enable a Coasts where this approach can be employed timely response (Appelquist et al. 2016). include areas with coastal defences, low-lying land, communities with a desire to improve flood or coastal West Africa context defence systems, communities with a sustainable- At community level, the cost of flood proofing for oriented coastal management attitude, coastlines properties at risk and shelters for at risk communities which require intertidal habitats, and where society is would normally depend on the number of properties aware of the benefits of managed realignment. The in the flood risk area and related costs, such as flood approach can adequately protect a coastal area or mapping and modelling exercises. However, in West infrastructure from erosion and flood risks (Mcglashan Africa, flood proofing is not an option that presents 2003). Nonetheless, it can be expensive, generate the best costs/benefits ratio. As coastal communities high political and social controversy particularly in West Africa represent a large percentage of the total when it involves relocating residents and subsequent population, flood proofing would require extensive confrontation with landowners. implementation, and prove costly. West Africa would also need to heavily invest in coastal surveillance and numerical modelling so that data and model results could predict extreme events and flood proofing, Solution n°14 : Managed realignment defences, low-lying land, desire to improve flood or coastal defence systems, sustainability-oriented Category coastal management attitude, need to create intertidal Hard engineering solutions [ ] habitats, and where the society is aware of the benefits Soft engineering solutions [ ] of managed realignment. Coastal planning and risk management Combining with other solutions techniques [ X ] Usually managed realignment requires a combination Compliance with nature-based solution criteria of hard and/or soft solutions (such as seawalls, dykes, Yes [ ] tidal marsh or dune rehabilitation) with coastal planning Maybe, under certain conditions [ X ] and risk management techniques (flood risk mapping, No [ ] coastal zoning, relocation). Substance and Purpose Assets, advantages and strengths particular to Managed realignment commonly includes setting back the West African coastal area the line of an actively maintained coastal defence to The approach can adequately protect a coastal area or a new line, landward of the original or preferably, to infrastructure from erosion and flood risks. elevated ground. This will increase the creation of intertidal habitat between the old and new defences. Constraints, weaknesses and difficulties particular to the West African coastal area Management realignment is therefore the deliberate It can be expensive and has to the potential to process of changing flood defences to allow flooding of generate high political and social controversy a defended area. particularly when it involves relocating residents and Main environmental requirements subsequent confrontation with landowners. & institutional context Appropriate in coastal areas with established coastal 58 relied on for coastal management practice. nursing grounds for marine fisheries while at the same time allowing some level of economic and recreational In the same way, flood shelters in West Africa as a activities (Appelquist et al., 2016). Additionally, coastal management practice to assist coastal communities zoning schemes can help maintain coastal livelihoods would not be the most beneficial because of high and biodiversity as well as broader economic activities density populations living on the coast. For example, in for the benefit of all communities and stakeholders Senegal, Gambia and Guinea-Bissau 80-100 per cent (Goussard and Ducrocq, 2017). of the population live less than 100 km from the coast (Hewawasam 2002). In addition, a comprehensive Barriers to implement coastal zoning systems relate to EWS would have to be fully operational to warn the the institutional capacity, available data and knowledge population to evacuate risk areas. in a given region. Before zoning is implemented, it is important to have a well-developed strategy for the 3.3.8. Coastal zoning overall scheme based on an ICZM approach. This includes obtaining broader support from affected General presentation communities through stakeholder involvement and consultations, to prevent systematic and repeated Coastal zoning is a land use system for regulating violations. development activities by dividing coastal areas into designated zones with different purposes and The cost of implementing a zoning system largely restrictions. Zoning requires a high level of coordination depends on the complexity of the system, the different and public participation and is regulated at different governance setups and the size of the coastal area in administrative levels. National guidelines can provide question (Appelquist et al., 2016). the broader framework for zoning while regional plans can be binding for local development and local West Africa context plans can handle the management of specific project Coastal zoning involves community participation and activities (Appelquist et al., 2016). is suitable in regions where conflict arises among Benefits and attention points communities with different ethnicities, classes and backgrounds. Great effort would be required to gain The advantage of coastal zoning is the ability to consensus among diverse communities. Additionally, manage multiple applications of the same coastal area West Africa has yet to invest in institutional capacity, to benefit all users with the potential to allow multiple data surveillance and knowledge for coastal areas to users benefit from services provided by coastal areas. adapt coastal zoning as an option. Zoning can be used to protect natural coastal areas and Solution n° 15 : Coastal zoning knowledge of the coastal area. Category Combining with other solutions Hard engineering solutions [ ] Just as flood and risk mapping was the cornerstone Soft engineering solutions [ ] of the diagnostic stage of ICZM, coastal zoning is the Coastal planning and risk management key tool for implementation of an ICZM plan. Coastal techniques [ X ] zoning is by nature intended to organise the use of different types of solutions. Compliance with nature-based solution criteria Assets, advantages and strengths particular to Yes [ X ] the West African coastal area Maybe, under certain conditions [ ] No [ ] Coastal zoning schemes can help maintain local coastal livelihoods, biodiversity and broader economic Substance and Purpose activities for the benefit of all communities and Coastal zoning is a land use system for regulating stakeholders development activities, dividing coastal areas into Constraints, weaknesses and difficulties designated zones with different purposes and restrictions. Coastal zoning has the ability to manage particular to the West African coastal area multiple uses of the same coastal area to benefit all The cost of implementing a zoning system largely users with the potential to allow multiple users to depends on the complexity of the system, the different benefit from services provided by coastal areas. governance regulations and the size of the coastal area Main environmental requirements in question. & institutional context Coastal zoning is a nature/community-based management practice that requires institutional capacity development, data surveillance and 59 60 Senegal. Photo: Vincent Tremeau/World Bank 61 MAP OF EXAMPLES OF SOLUTIONS IMPLEMENTED IN WEST AFRICA COASTAL AREA Zoom on the two regions with a high density of implemented solutions (the list of 29 location references applies to both the local maps below and the general map above) 62 N° LOCATION TYPE OF SOLUTION 1. . . . . . . . . . . . . . . . . . Lomé . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Offshore Breakwater 2. . . . . . . . . . . . . . . . . . Abidjan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Offshore Breakwater 3. . . . . . . . . . . . . . . . . . Petite côte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Offshore Breakwater 4. . . . . . . . . . . . . . . . . . Cotonou. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Offshore Breakwater 5. . . . . . . . . . . . . . . . . . Cotonou. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Groynes 6. . . . . . . . . . . . . . . . . . Keta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Groynes 7. . . . . . . . . . . . . . . . . . Sakumono . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Groynes 8. . . . . . . . . . . . . . . . . . Elmina . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Groynes 9. . . . . . . . . . . . . . . . . . Ada. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Groynes 10. . . . . . . . . . . . . . . . . New Takoradi. . . . . . . . . . . . . . . . . . . . . . . . . . . . Groynes 11. . . . . . . . . . . . . . . . . Petite côte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Groynes 12. . . . . . . . . . . . . . . . . Lagos. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Groynes 13. . . . . . . . . . . . . . . . . Elmina . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Jetties 14. . . . . . . . . . . . . . . . . Cotonou. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Jetties 15. . . . . . . . . . . . . . . . . Lagos. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Jetties 16. . . . . . . . . . . . . . . . . Accra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Revetments 17. . . . . . . . . . . . . . . . . Saint-Louis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Revetments 18. . . . . . . . . . . . . . . . . Rufisque. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Seawall 19. . . . . . . . . . . . . . . . . Serekunda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Seawall 20. . . . . . . . . . . . . . . . . Lagos. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Beach nourishment 21. . . . . . . . . . . . . . . . . Banjul. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Beach nourishment 22. . . . . . . . . . . . . . . . . Kololi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Beach nourishment 23. . . . . . . . . . . . . . . . . Nouakchott . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dune rehabilitation 24. . . . . . . . . . . . . . . . . Djimda (Fatick). . . . . . . . . . . . . . . . . . . . . . . . . . . Wetland restoration 25. . . . . . . . . . . . . . . . . Guagué Sherif . . . . . . . . . . . . . . . . . . . . . . . . . . . Wetland restoration 26. . . . . . . . . . . . . . . . . Accra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Early flood warning system 27. . . . . . . . . . . . . . . . . Lagos. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Early flood warning system 28. . . . . . . . . . . . . . . . . Grand-Lahou. . . . . . . . . . . . . . . . . . . . . . . . . . . . Relocation 29. . . . . . . . . . . . . . . . . Abidjan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Relocation 63  loating agricultural 3.3.9. F Benefits and attention points management While this is obviously the cheapest and most environmentally friendly option for many parts of developing regions such G eneral presentation as West Africa, the costs for people, tourism, industry, Floating agriculture is a way of utilising waterlogged areas infrastructure must be weighed against the benefits of for long periods in food production. This technology is allowing an area return to its natural state. If the costs greatly aimed at adapting areas that experience more regular or outweigh the benefits, for example by having to relocate prolonged flooding. The approach employs beds of rotting people or losing valuable facilities, then other options must vegetation, which act as compost for crop growth. The be considered. beds are able to float on the water’s surface, thus creating It is also necessary to take into account the process of areas of land suitable for agriculture within waterlogged settlement littoralisation and activities. A ‘do nothing’ policy regions. Scientifically, floating agriculture is referred to as would be difficult to implement in an attractive coastal area. hydroponics. As an inexpensive management option, it requires either a Benefits strong policing power on the part of institutions or strong dialogue with local communities, and probably both. This Floating agriculture helps mitigate land loss through flooding option is not suitable as a solution in all coastal areas. by allowing cultivation to continue. In this way, the total area for cultivation can increase, allowing communities to West Africa context become more self-sufficient. Additionally, the area under In areas with little at stake, either human, economic, or floating cultivation is up to 10 times more productive than ecological, ‘doing nothing’ is the obvious solution and traditionally farmed land (Haq et al., 2004) with no additional usually spontaneously applied, although not usually chemical fertilisers or manure required. After the crops are the result of real political reflection. harvested and floating rafts are no longer required, they can be used as organic fertilisers or incorporated into the following years’ floating beds as a fertiliser (AEPIS and CONCLUSIONS FOR 3.4.  RIPSO, 2004; Saha, 2010). COASTAL MANAGEMENT While the system is labour intensive, it also has the capacity PRACTICES IN WEST to provide employment opportunities within communities (Haq et al., 2004). As both men and women can carry AFRICA out floating agriculture practices, it can also lead to Coastal solutions applied until this point in West Africa improvements in gender equity. While this technology works are in the main HES, consisting of building structures to well in some areas, it is unclear how it may be affected by artificially stabilize the coastline. However the unaffordable rising sea levels and increasing salinity, which are likely to cost and collateral effects raise questions today about occur with climate change events. the systematic use of this type of environmentally invasive management. Faced with this observation, SES and coastal West Africa context planning emerge as an option for sustainable coastal zone management. SES are frequently used to combat The system appears to be suitable for low lying areas coastal erosion and flooding in West Africa but remain of West Africa prone to waterlogging for long periods. underdeveloped in the region. According to the literature, Adopting the system would help empower communities to coastal planning and risk management techniques, essential produce products, while engaging men and women in work for the protection of populations, indicate that these tools that enables self-sufficiency. could be better exploited. The two maps on page 62 represent about thirty examples  on-intervention/do 3.3.10. N of solutions implemented in West Africa, divided into nothing the three categories mentioned - HES, SES and coastal planning. The preponderance of recourse to HES is clearly General presentation visible. The map highlights areas where the coast appears particularly vulnerable to erosion and flooding, the northwest Doing nothing to combat the effects of flooding and Atlantic coast and the northern Gulf of Benin. In comparison, erosion means simply ignoring events as they occur. the muddy coast seems less sensitive to coastal risk This is normal in areas where there are no people, so nothing vulnerabilities. There are two factors to be considered of economic or institutional value requires protection. The here: (1) The coastal area shows a long continental shelf ‘do nothing’ approach aims to deal with natural events, with low to moderate energy waves, permanently supplied for example loose land falling into the sea, but without with sediments from small but numerous coastal rivers and loss of infrastructure or lives. The ‘do noting’ management is not vulnerable to erosion. (2) Political instability in some option consists, in a deliberate and thoughtful way, of not countries in the region over the last few decades hampered field studies and led to a lack of scientific literature on the intervening against risks. topic. 64 INTEGRATED COASTAL 4.  MANAGEMENT Ghana. Photo: Hen Mpoano Integrated coastal management (ICM) is not a solution but rather its purpose is to provide principles to guide the design and implementation of a solution or, a set of solutions to manage or protect a given portion of the coast and shoreline in the most effective and possible manner. This takes into account all relevant dimensions and constraints, human, environmental and economic. The issues to be addressed in ICM when carrying out a coastal management intervention (Olsen, 2003) are listed below: 1. Identify stakeholders and identify and assess the ICM goal definition.  repare an ICM plan, including gathering of best scientific data related to issues, the precise definition of 2. P boundaries, the search for solutions and the best combination of solutions, and the definition of an action plan for applying solutions, which may be expressed as a management scenario.  onsult with stakeholders and decision-makers, completion of an environmental and social 3. C impact assessment, plan implementation and establish the institutional capacity to support the plan’s deployment.  lan implementation, including investment and infrastructure building according to planned 4. P time-schedule.  nsure ‘ex-post’ real-time monitoring followed by a global evaluation sometime between five and 5. E 10 years. While the above points are not specific to coastal management, many points raise the need for special attention to address coastal management intervention or any public action dealing with coastal environment. Since the 1980’s, ICZM is used to as an approach to guide coastal environmental issues in a coherent manner. It is from an ICZM approach that the authors raise the key elements presented below. Before going further in presenting an ICZM design and implementation process plan, it is important to recall prior needs in terms of an institutional framework. To increase the chance of success it is necessary to have clear legislation, political legitimacy for the decision-making framework, and the adoption of a national public policy document favourable to coastal management - all conditions which will allow the launch of an ICZM plan. 65 4.1. THE ICZM APPROACH Threats can affect the physical, ecological, economic or social settings of the environment and it is A broad and commonly accepted definition of ICZM necessary to define hazards for further analysis and is that it consists of an adaptive, multi-sectoral characterisation. governance and technical approach which aims to take into account in a balanced way, the objectives, Following hazard identification, a vulnerability development and protection of the environment in the assessment is required to identify features susceptible coastal zone (UNEP, 2009). to damage, including ecosystems and artificial structures. Social variables, including demographic profiles and sites such as hospitals and schools,  iagnostic survey and 4.1.1. D which are potential human mortality hotspots, need objectives identification to be defined. One of the main challenges implementing an Within the defined area it is important to identify and ICZM plan is the diagnostic quality of the hazard or characterise damage and impact of prior disasters processes to be managed. ICZM stresses the need as well as potential future impacts such as coastal for a broad diagnostic, covering in-depth scientific flooding, riverine flooding, landslides, cyclones and knowledge about the issue, the cause chain and tsunamis. the potential impact on environmental, social and economic aspects that these issues pose now or Risk assessment is a source for diagnosis and in the future. This should include a whole range of calculated by correlating information derived from a economic activities including agriculture, fishing, hazard assessment and a vulnerability assessment, industry, transport, housing, tourism, etc. with a formula of - hazard + vulnerability = risk. Estimating the probability of occurrence is used A recent approach recommends that diagnostics to analyse hazards along with magnitude and should be carried out by experts, stakeholders and loss incidence, which can be calculated in both public decision-makers for a participative approach, quantitative or qualitative terms. Event frequency is an documenting opinions, perceptions and expectations. important indicator of past and future loss patterns. A definition of the project’s area/management unit As cumulative implications are important, the analysis boundaries on land and sea should be delineated must consider not only a large event such as a cyclone before implementing integrated management activities or tsunami, but also multiple and less severe events or policies. The management units’ role is to specify a such as storms. Yearly losses over a 10 or 20-year coastal territory area on which an integrated, relevant time frame from smaller events may equal or even and effective management plan can be executed. The exceed the losses from a large event. role of the unit is to respond to issue(s) raised by the The probability of occurrence is based on frequency, community related to the targeted geographical area. which is documented by historical records and However, it is important to take into account not only scientific evidence. The time period for re-occurrence the spatial extent of the issue whether a shoreline is based on criteria selected for a specific plan, for retreat or different issue, but the extent of the natural example over a 30-year period where the frequency processes at the issue’s origin, and the level at which can be classed as high, medium or low probability. public action needs to be mobilised to take action, by controlling the cause or mitigating its impacts (Balaguer et al., 2008). Very often, several activities Building scenario and 4.1.2.  need to be combined for the effective management of designing ICZM plan a given stretch of coastline. Because the complete diagnostic survey of the Identifying the objectives of an ICZM plan is an coastal section leads to a multidimensional body of important step only achieved by employing a knowledge, and because, on the other hand, it is participatory approach, which allows for a sense of likely that there are several possible solutions and ownership and also allows for stakeholders to prioritise means to achieve the management objectives, the activities and key areas that need to be addressed. It construction of the integrated coastal management also allows for decisions on whether selected areas plan will take a complex form. For instance, the choice will or will not benefit from the same protection effort of appropriate defence solutions or mitigation tools or whether these areas need to naturally evolve in use such as coastal management practices researched in and function. this compendium, including SES and HES and coastal planning, should lead to in-depth discussion Identifying hazards threatening key areas is an among expert groups. This can be followed by debate important next step. Threats vary within comparatively between experts on one side and stakeholders and short geographic distances and not all hazards communities on the other side. constitute important threats to each community. 66 For this reason, it is recommended to employ a Implementation, 4.1.3.  method capable of representing a synthesis of scientific knowledge processes, a range of possible monitoring and evaluation management solutions and the different ways that data Once an ICZM plan is decided, it is important to ensure was combined into the formulation of an integrated that national and local institutions take ownership and management plan. This will indicate the possible develop the capacity to implement the plan efficiently. impacts, whether positive or negative, in the plan In some cases, institutions need support to reach the where building scenarios, which can be supported by required level of management capacity. ICZM places modelling and computer tools, allows such syntheses great importance on these institutional aspects, to be made (Carrero et al., 2013). which are considered vital for the longevity of any management plan. As ICZM recommends a participatory approach to achieve transparency and social support for the Routine monitoring including data collection and decision-making process in the planning phase, identifying indicators will be used to measure initial developing and discussing possible scenarios objectives and report on achievements over the contributes to a realistic application of ICZM principles following years. Appropriate institutional arrangements (Cicin-Sain et al., 1998), such as periodic meeting and procedures should accompany the ICZM’s implementation plan and phase. Monitoring and evaluation over the lifetime of the project should influence decisions to adapt the plan as necessary and to correct negative social and environmental trends. A final independent programme evaluation should take place between five and 10 years after the project’s completion. Diagnostic survey and identification of objectives Participative definition of objectives Participative Diagnostic Scientific assessment of the hazards Data, knowledge, and objectives Building scenarios and designing ICZM plan Creating scenarios Feeding scenarios with participative insights Computer tools (GIS, modeling) Presentation of scenarios to stakeholders and communities Participative debating of scenarios Designing the ICZM plan (based on the best scenarios) by decision makers Implementation monitoring and evaluation Implementation of the concrete solutions Implementation of the concrete solutions [ either HeS or SeS ] [ either HeS or SeS ] Setting up the new policies and/or the coastal planning techniques Monitoring the impacts, taking decisions for adaptive management Evaluation after several years with regards to the initial objectives Figure 4: Framework of ICZM implementation process on a given coastal territory. 67 ECOSYSTEM-BASED 4.2.   nderstanding of the cumulative impact of 4. U different activities affecting an ecosystem. MANAGEMENT: NEW  anage and balance multiple and often 5. M PRINCIPLES FOR conflicting objectives related to different benefits and ecosystem services. COASTAL ZONE  mbrace change, learning from experience, 6. E MANAGEMENT and adapt policies throughout the management Ecosystem-based management (EBM) is a general process framework not dedicated to a coastal domain but can be successfully applied in coastal zone Although application of EBM can and should vary management. When applied to the coastal zone, according to the local context, some basic steps or EBM does not appear to be an alternative to ICZM, components may include (derived from Tallis et al., but a complementary approach (Nobre, 2011). EBM 2010).: integrates some of the principles and concerns of  coping, including acquisition of data and 1. S ICZM, such as adaptability, its ability to be multi- knowledge from various sources to provide a sectoral and a willingness to improve decision- rigorous understanding of critical ecosystem making processes. Additionally, EBM deepens and components. clarifies certain issues, particularly recognising the  efining ecological, social and economic 2. D preservation of ecosystem functions, as it considers objectives. humans live within ecosystems, not outside. As such EBM can be seen as an environmentally responsive  efine indicators and set target values which 3. D policy option for the development of an ICZM, which would represent a desired level of ecosystem involves systematically prioritising ecosystems’ health as an expression of the ecological conservation when making choices to balance objectives. economic and ecological objectives. EBM is based  isk analysis of threats and disturbances, both 4. R on the implementation of NbS or SES, over HES. In natural and human, and effects on the indicators. this sense, EBM could be considered an eco-friendly mplementation of the EBM plan by employing 5. I version of ICZM and is believed be scientifically more measures and solutions mainly based on nature advanced. The understanding of the ecological (NbS), at times by involving SES. Monitoring and processes such as trophic chain and biodiversity will evaluating EBM strategies effectiveness. need to be more fully covered in EBM at the time of the diagnostic study and as part of monitoring. EBM is well suited to balancing the diversity of competing interests and functions placed on One widely accepted definition is that marine EBM coastal areas, due to its holistic approach to the is an integrated management approach which uses use of, threats to, and services provided by coastal the full array of interactions within an ecosystem, ecosystems. It is also well suited to collaborative including humans, rather than considering single planning and decision making, when stakeholders issues, species, or ecosystem services in isolation are actively involved. Finally, EBM can effectively (Appelquist et al., 2016). The goal of EBM is to consider ecosystem health and incorporate options maintain an ecosystem in a healthy, productive and for sustaining the services ecosystems provide to resilient condition so that it can provide the services human well-being into coastal management plans communities want and need. and activities. Key principles behind the application of EBM in Different ecosystems vary greatly and experience coastal areas include (Appelquist et al., 2016): varying degrees of vulnerability and so present  lear and concise goals that move beyond 1. C challenges in applying a functional framework, which exclusively science-based or science-defined can be universally applied to all ecosystems. The objectives to include social and cultural steps or components of EBM outlined above can importance. be applied to different ecological contexts and are 2. C  onnections among marine, coastal and suggestions for improving or guiding the challenges terrestrial ecosystems, as well as between involved with managing complex issues. As a result ecosystems and societies. of copious influences, impacts, and interactions to account for within EBM, a number of challenges to  cosystem service provision to generate basic 3. E implement the plan exist. goods, for instance food and raw materials, as well as crucial services, including protection As ecosystems differ greatly and express varying from extreme weather, fishing spawning areas, degrees of vulnerability, it is difficult to apply a carbon sequestration, etc. universally functional framework. The outlined components of EBM can, for the most part, be 68 applied to multiple situations and are suggestions management rules were established such as for improving or guiding the challenges involved with laws, policies, protocols and agreements. The first managing complex issues. Because of the myriad documented law on the Volta River Basin in Ghana influences, impacts, and interactions that need to was the 1903 River Ordinance (Opoku-Agyemang be taken into consideration - issues, obstacles and 2001) to manage several of the country's rivers, criticism often arise within EBM. including the Volta, and the powers of control over the river conferred by colonial governments. Located Despite the suitability of EBM, its approach is subject in the south-eastern part of Ghana between 0° 40’ E to limitations such as the definition of geographic areas and 1° 10′ E and 5° 25’ N and 6° 20’ N, the Ghana’s for management and difficulty in applying a universally Volta Delta covers an area approximately 4,562 accepted functional framework. Nonetheless, current km2 (Appeaning Addo et al. 2018) (Fig. 5) and lies and future environmental challenges facing ocean and within the Keta Basin, one of several fault-controlled coastal areas in West Africa stand to benefit from EBM sedimentary basins in West Africa (Appeaning Addo as it allows for resource trade-offs to help protect and et al. 2018). sustain diverse and productive ecosystems and the services they provide. Examples of EBM and case The Volta River is a main source of sediment supply studies are outlined for specific places managing to the Gulf of Guinea, but its activities have been coastal habitats including mangroves, sand dunes, and interfered with by anthropogenic pressure. The river's salt marshes to shield communities and infrastructure discharge varied from 1,000 m3/s in the dry season against storm surges, or to ensure forest systems to over 6,000 m3/s in the wet season before the remain healthy and continue to provide clean drinking Akosombo Dam was completed in 1965 (Anthony et water despite changing conditions (Cohen-Shacham, al. 2015). Runoff before the dam was built amounted 2016). In Kampong Bay Basin, Cambodia, a climate to 87.5 mm/year and decreased to 73.5 mm/year vulnerability study allowed planners to analyse varying after the dam was built (Oguntunde et al. 2006). The climate change projections and relevant management natural flooding patterns in the area changed due to responses; in turn, this allowed managers to evaluate the controlled flow of water. In addition, the annual trade-offs among specific management measures transport of sediments was drastically reduced by (UNEP, 2011). EBM is therefore a broad management the construction of the dam to only a fraction of the approach, and if considered could result in improved original amount, without peaks in the flow discharge coastal management in West Africa. (Bollen et al. 2011). The delta comprises extensive wetlands, interspersed with areas of short-grass, The authors believe that EBM is well suited to, and what mainly, red mangroves, and savannah forests (Manson is close to, an ideal coastal management approach for et al. 2013) and composed of fragile biophysical the West Africa coastline. EBM balances diversity of characteristics affected by the construction of dams competing interests and functions placed on coastal on the Volta River and sand extraction, among other areas, due to its holistic approach of threats to, and anthropogenic activities. The altered ecosystem services provided by coastal ecosystems. It is also well adversely affects livelihoods, although efforts were suited to collaborative planning and decision making, made to reduce these impacts, both in terms of due to the active involvement of various stakeholders. infrastructure and policy. Climate change-related events such as rainfall variability, marine and river As ecosystems differ greatly and express varying flooding, drought, rising sea levels, storm surges and degrees of vulnerability, it is difficult to apply a universal temperature increases are some of the natural factors functional framework. The outlined components of changing biophysical conditions in the delta system EBM can, for the most part, be applied to multiple (Appeaning Addo et al. 2018). Erosion in the Volta situations and are simply suggestions for improving Delta was first reported in 1929, but it is assumed that or guiding the challenges involved with managing it existed as far back as the 1860s, particularly in Keta complex issues. (Nairn et al. 1999). THE VOLTA DELTA AS A 4.3.  The construction of Tema harbour in 1955 caused the diffraction of sea waves on land along the eastern HOTSPOT: A POTENTIAL coast of Ghana, causing massive erosion (Ly 1980; SUITABLE CASE FOR Tsidzi and Kumapley 2001). Erosion rates of about 4 m per year before dam construction increased to about EBM APPLICATION IN 8 m per year post-construction (Ly 1980). To address WEST AFRICA erosion impacts, the central government launched Keta and Ada sea defence projects in 2001 and 2013 There is no explicit national policy devoted exclusively respectively. These were preceded by community to the Volta Delta. However, various policies applied to attempts to protect the coast in and around Keta, certain areas ensure conservation and preservation. led by traditional leaders and local government, since During colonial and post-colonial periods, formal 1923. Early defence structures from the colonial era 69 flooding (Anim et al. 2013); oil and gas exploration which is expected to increase the rate of subsidence (Setordzi and Nyavor 2015) and the extraction of coastal sand with the potential to reduce sediment balance and increase erosion (Appeaning Addo 2015; Appeaning Addo et al. 2018). There is transition in the Volta Delta from the Holocene to the Anthropocene. It is evident that human activities have greatly altered the physical characteristics of the delta area where buildings and infrastructure further reshape the nature of human settlement, livelihoods and movements. The Figure 11 - Volta Delta coverage in Ghana construction of the Akosombo and Kpong Dams had a huge impact on socio-economic were built with weak local materials unable to withstand adjustments to people's livelihoods, affecting the strong sea waves (Akyeampong 2002; van der Linden sedimentation process which repositioned the river et al. 2013). After Ghana's independence in 1957, the mouth along the Gulf of Guinea and reduced the government launched a coastal protection project quantity of freshwater flowing into the sea. Additionally, in 1960 using steel sheets to protect approximately the numbers of fish flowing from upstream decreased 1,600 m of Keta Municipality, but the sheets corroded considerably resulting in a migration from the delta to rapidly (van der Linden et al. 2013). In the early 2000s a upstream areas for freshwater fishing. US$83 million coastal protection project was required to stabilise Keta's coastline (Ly 1980; Boateng et al. Similarly, the construction of a fishing harbour in 2011). Tema, west of the delta, impacted on erosion rates and livelihoods in the delta region. The harbour and By 1996, the rate of erosion and flooding increased associated industrial city adversely affected the fishing (Fig. 6), with more than half of Keta and the surrounding livelihoods of migrants from the delta when the dams cities under water (Ile et al. 2014), displacing more were constructed. The construction of groynes along than 10,000 people in communities within Keta and the coasts of Keta and Ada resulted in significant resulting in the loss of millions of dollars (Oteng- rates of accretion, reshaping the morphology Ababio et al. 2011; Danquah et al. 2014). The central along the coast. The Keta Sea Defence Project government subsequently undertook a sea defence and accompanying resettlement plan continue to project to build a roadway across the Keta lagoon to impact on the delta’s physical nature, and on human link to the coastal highway, reclaimed land, and built mobility. The revetment construction at Atokor in Keta houses to resettle displaced people (Danquah et al. Municipality enabled the reconstruction of a previously 2014). Between 2001 and 2004, six groynes were destroyed road and opened the area to commercial built in the Keta area to prevent erosion and control activities. Human settlements, land use and economic flooding of buildings between the Keta lagoon and the activities continue to reshape the land cover and sea (Boateng, 2009). The groynes were approximately biosphere of the delta area. 190 m long and 750 m apart (Nairn and Dibajnia 2004). In 2011, the Government of Ghana began The Volta Delta example clearly argues for a multi- construction of a 30-km marine defence wall in Ada spatial scale design to take into account integration to protect communities from wave action (Anim et al. issues and mitigation strategies, from river discharge, 2013). The effects of the defence structures resulted to the re-distribution of sediment at regional and local in accretion on the upstream side and increased scale, with lands at different levels of urbanization erosion on the downstream side of the coast (Wiafe et implying different need/effort for a sustainable solution al. 2013; Appeaning Addo 2015). (Alves et al., 2020). River flow management for hydropower and agriculture management for example In recent times, groundwater extraction for irrigated the Nile, Mekong, Mississippi etc. requires regional agricultural practices, which has the potential to agreement between states, necessitating a strong increase the scale of sinking in the delta at a rate of collaboration between all coastal management actors approximately 1 mm per year, is similar to other deltas along the sediment cell for efficient and effective around the world (Kortatsi et al. 2005; Appeaning Addo coastal management. et al, 2018). Wide practices are taking place including mangrove harvesting which can lead to erosion and 70 SUMMARY AND 5.  RECOMMENDATIONS Ghana. Photo: Andrea Borgarello/World Bank Coastal areas are home to natural marine processes and habitats, and also locations for human activity, which occur inshore, offshore and inland. Inland activities can impact on coasts through changes in catchment areas linked to the coast where assessments reveal that actions in one location impact in other locations. The development of any ICZM must take all components into account as the basis for holistic planning to ensure a more sustainable approach to coastal management that link users/processes together, rather than focusing on a single particular issue. 5.1. KEY PRINCIPLES 5.1.1. Consider at least two spatial scales From Mauritania across the Gulf of Guinea to the tip of the Gulf of Benin, coastal management should be envisaged through a system dividing the coastline into areas. This division into zones must refer to at least two nested scales: • A large scale zone to study the cause and dynamics of meteo-oceanic and hydro-sedimentary events. •  local scale zone to study local geomorphological conditions, erosion, societal and ecological issues and A collaboration with institutions managing the jurisdiction. Large scale studies create a greater understanding and knowledge of a zone and requires a corresponding level of international management. Work on the Langue de Barbarie situated in Saint- Louis, northern Senegal would also affect the construction of ports and jetties on the Mauritanian coastline and slow down sediment transport through coastal drift. This would also affect management of the Senegal River basin, originating from dams located in Mali and would require a regional international organisation to manage work on the Langue de Barbarie. Local scale studies typically implement HES and SES defensive solutions, risk management systems or measures including warning systems and zoning policy. It is important that activities are coordinated to avoid communities making local decisions when those decisions can lead to cancelled plans for other communities living downdrift. Local institutions are in the best position to ensure coordination, provided the institutions have legitimacy and base local decisions on a national legal framework. Support from national or international donors will also be necessary in cases where serious issued need to be addressed. 71 A local scale may correspond well to sectors (n=179) the possibility of flooding certain agricultural areas defined and monitored by the West African Coastal from time to time (while implementing measures to Area Master Plan surveys (UEMOA, MOLOA, IUCN, limit damage to crops). 2010), either considered one by one or in small clusters of two or three units. To facilitate decision- The choices and compromises that govern making, it is preferable that the precise boundaries management objectives must result from a of these coastal management zones correspond to participatory process, seeking the greatest possible local administrative borders, which does not exclude consensus. The choice of technical solutions and how several contiguous zones working in a concerted to implement proposed solutions can be left to the manner if the same environmental conditions and next stage. issues are in place. Build scenario for future 5.1.3.   efine clear objectives in a 5.1.2. D by using single or several participative way solutions Once an area of interest is defined, any planned In most coastal areas, achieving management management action must be based on a shared objectives requires a combination of solutions, diagnosis and a clear definition of objectives, based on regardless of whether HES, SES or CPT are a participatory approach. Such an approach requires employed. A significant design exercise is required already established stakeholders, those who live in over time to decide on how to arrange and implement the area and are directly interested in the area’s future, solutions. Drawing up different scenarios will allow and those who manage activities in the larger region for a comparison of advantages and disadvantages and who could favour or compromise management in terms of cost and performance, and ensure efforts. Stakeholders should include economic the objectives are achieved to complete the task. actors and people who use the coastal territory - Decisions should be based on the best available hotel managers, resource users, waste emitters etc. scientific data, much of which will documented Agreement and adoption of key objectives will require before the diagnostic phase. However, additional field a certain level of compromise. studies may be required to ensure there is sufficient data to develop modelling scenarios with accuracy, The area of interest will be defined as a local zone, or for example to simulate new current patterns or new a few contiguous zones sharing the same issues on sediment flows. In addition, scenario building should a coastal stretch extending over a distance ranging use a multi-spatial scale approach as some issues may from five to 50 kms. be local, but many causes originate at regional level Diagnosing issues in an area of interest requires a where regional measures or solutions are frequently shared recognition by the different Actors, where the required. The scenario comparisons will offer a choice diagnosis is based on the best available knowledge of two to three preferred options, which will then be and data. This must cover a wider area beyond the presented and explained to stakeholders to choose area of interest to allow a complete analysis of the the best option. Where possible, preference should physical mechanisms and causes, whether natural or be given to solutions moderate in cost, long term and man-made. with minimal collateral environmental damage. At the end of this double diagnosis, the next phase is Once a best-compromise scenario is identified and to define the relevant management objectives to be adopted, the project team will draft an implementation addressed. It is expected at this point that the overall schedule for the plan. The plan should illustrate long-term vision(s) for the area – agriculture, fishing, each solution, explaining the technical, budgetary industry, tourism, residential, nature conservation and administrative constraints, the timeframe for were discussed and endorsed, by stakeholders, implementation, and the potential company chosen local communities and national government. Once an to implement the plans. If the plan requires large scale agreement is established, the next step is to define tasks for example on a river basin scale, interested the objectives’ broad plans, in line with the general governments and bodies with the capacity to take vision for the area. Examples can include where one the appropriate measures on a large scale need to be objective may be to save as many houses as possible approached. and relocating those that cannot be saved (by financing reconstruction elsewhere); or to save a beach in Implement the plan 5.1.4.  an area important for tourism, while accepting loss elsewhere. Other examples would require a decision sustainably and adaptively to maintain communication infrastructure or to accept A crucial factor enabling national and local institutions the possibility that certain aspects will be destroyed to take ownership of the project at the outset requires by the sea; to defend all agricultural areas or accept each actor to be aware of his/her role according to the 72 Senegal. Photo: Vincent Tremeau/World Bank implementation schedule. In some cases, institutions Long-term monitoring requires setting up observation may require support to reach the necessary level of stations, suitable equipment, and efficient maintenance management capacity - a key point for the plan’s and data collection. sustainability. It is important to promote an observation network, Once this checklist is complete, the implementation data centralization and open data sharing according phase can begin. This can involve time consuming to the FAIR principles (find, access, inter-operate, infrastructure construction, launching of an early reuse) to allow for monitoring in the area, on a regional warning and shelter procedure, or setting-up a new scale and also throughout West Africa. Monitoring land-use planning policy for the targeted coastal area. should not be limited to environmental and social data It is important to establish a monitoring and control collection but should also bring together management framework, which allows operations to be monitored experience results carried out in the beneficiary areas, and adapted as necessary. The methods and schedule to capitalize on lessons learned. Close collaboration for monitoring and evaluation, and procedures for between managers and academic institutions can revising the plan should be clearly defined. enable documentation of acquired knowledge. This allows development of, and contributes to, new It should be noted that a plan based on a flexible management guidelines which will strengthen existing scenario using various solutions and working in education curricula for master degrees, doctorates combination with different time frames, can help to and thematic workshops, providing a valuable anticipate change. A rigid plan, even one well suited complementary policy. to the current pressure or context for example sea levels or population density, may fail with changing demographics or climate change. TABLE SUMMARIZING 5.2.  SOLUTIONS  ollect data and maintain 5.1.5. C The remainder of this chapter provides a table strong links with the summarising the name, main characteristics, degree of compliance with NbS principles, advantages and scientific and disadvantages, and implementation examples in West educational networks Africa for each solution. 73 “NbS” if Coastal Where applied Ref. in compliant management Characteristics Advantages Disadvantages in West Africa text with NbS practice and (examples) principles definition 3.1.1 Offshore breakwater: i. intercept and i. reduces coastal i. expensive  ogo – between i. T shore-parallel hard reduce incoming erosion Kpeme Gumukope equires high level of ii. r engineering protection wave energy at the and Aneho equires basic ii. r technical knowhow structures situated just shoreline monitoring and  bidjan ii. A offshore of the surf  nderstanding of iii. u maintenance (Ivory Coast) zone the area’s wave iii. construction of transmission is iii. Benin shorter breakwaters required iv. Saly, Senegal in series allows some wave action at the coast, which can be beneficial for recreation 3.1.2 Groynes: narrow, i. commonly located i. material selection he ideal design is i. t i. Keta, Sakomono, shore-perpendicular on drift-aligned can be tailored to rarely achieved, with Ada, New Takoradi, generally solid and coasts where local availability a resulting negative Elmina – Ghana durable hard structures erosion problems impact on downdrift ii. ideally designed ii. Togo designed to interrupt are generated by coastlines through groyne field allows longshore sediment gradients in the sediment starvation Cotonou – Benin iii.  sediment to transport thereby longshore transport and erosion further accumulate and iv. Senegal (Petite trapping a portion of downstream ii. dimensions eventually bypass Côte) the sediment which is between groynes the buried groyne, elatively expensive, ii. r otherwise transported v. Nigeria length and spacing without causing depending on alongshore. generally varies significant downdrift material used for from 1:4 on sandy erosion construction beaches to 1:2 on trap sediment to iii.  gravel beaches widen beach width length should be iii.  for recreation and approximately 40- tourism 60% of average surf iv. reduced erosion zone width and greater wave energy dissipation. 3.1.3 Jetties: hard i. typically larger  nsure robust and i. e  ay not allow i. m i. Takoradi harbour, structures constructed and also extend reliable stabilisation beach formation Elmina — Ghana at the banks of to greater offshore of tidal inlets or river ii. aesthetically ii. Port of Lomé – Togo tidal inlets and river distances than mouths displeasing mouths designed to groynes Cotonou – Benin iii.  ii. control the trap a portion of the ii. constructed from development of Bight of Benin iv.  longshore sediment a wide variety of unwanted features transport, thereby materials including which can obstruct stabilising the inlet rock armour, open channel to and preventing the concrete, dolos, the sea channel’s siltation tetrapods and steel piling 3.1.4 Revetments: i. generally solid, i. reduces shoreline i. aesthetically i. Jamestown, Labadi Designed to dissipate durable, shore- erosion displeasing – Accra (Ghana) and reduce wave parallel, sloping  hoice of materials ii. c ii. Saint-Louis, action at the boundary structures, affects durability Senegal between sea and land constructed landwards of the iii. Grande Corniche beach (Dakar, en projet) ypically protect a ii. t soft landform (dune area, coastal slope, dyke or seawall) iii. materials used include logs, wood planks, fence rails, fascines, gabions, hurdles, sods, or stones. 3.1.5 Seawalls: designed i. b  uilt parallel to the i. prevent further i. n  ot a permanent  ufisque, Diokoul – i. R to prevent soil sliding, shore shoreline erosion solution to coastal Senegal while providing erosion  sually used in ii. u  ct as coastal flood ii. a ii. Keta, Ghana protection from wave areas where further defences  eneral reduction of ii. g action shoreline erosion available sediment vertical seawalls use iii.  will result in extreme in the coastal cell less space hence, damage reduce construction iii. down-drift erosion cost iv. basal scour v. beach down-draw affects accessibility vi.  to the sea 74 “NbS” if Coastal Where applied Ref. in compliant management Characteristics Advantages Disadvantages in West Africa text with NbS practice and (examples) principles definition 3.1.6 Dykes: Designed to i. sloped seaward i. greater wave i. requires large have a high volume, edge and crest energy dissipation volumes of which helps to resist heights and reduced building materials – water pressure, sloping wave loadings on expensive ii. geotechnically sides to reduce wave structure stable under normal ii. construction loadings and crest and extreme ii. enable economic requires significant heights sufficient to conditions and socio- areas of land prevent overtopping by economical flood waters activities at high water levels 3.1.7 Storm surge barrier/  an be movable i. c  ffectively reduce i. e  igh capital and i. h closure dam: or fixed barriers or the height of maintenance costs Capable of protecting gates extreme water levels ii. movable barriers tidal inlets, rivers in the area behind  urge barriers are ii. S also require and estuaries from the barrier movable or fixed simultaneous occasional storm surge barriers or gates ii. reduce both investment in flood events which are closed construction and warning systems when an extreme maintenance costs can cause flooding iii.  water level is for defenses on the on the landward forecast landward side of side of the barrier these structures iii. Closure dams when river levels are fixed and are high or remain permanently close closed for extended off a river mouth or period estuary 3.1.8 Land claim i. more aggressive i. gain additional  auses the direct i. c i. Keta project (Ghana) (or reclamation): form of coastal coastal land for loss of intertidal  ko Atlantic City, ii. E to create new land protection agriculture or habitats such Nigeria from areas that were development as saltmarshes, previously below high purposes intertidal flats and tide for agricultural or sand dunes development purposes ii. increase the tidal range upstream iii. can introduce contamination to the coastal zone and acidification of coastal waters. 3.1.9 NbS Cliff stabilisation:  atural processes to i. n i. more sustainable i. it interferes with i. Senegal smoothing and protect the shoreline and sometimes the natural coastal (in some regrading of sloping against flooding and cheaper dynamics cases) soft rock coasts to erosion ii. improved public ii. smoothing and stabilise the coastline  ay involve the ii. m safety regrading of slopes addition of extra causes land loss iii. maintains the sediment from other amenity value of may cause erosion iii.  sources these areas in the long run 3.2.1 NbS Beach nourishment: i. r ebuild and maintain i. accentuates wave i. d  oes not provide a he bar beach of i. t involves beach the sandy beach energy dissipation long-term solution Victoria Island in recharge, beach for wave energy Lagos (Nigeria) ii. preserves the epetitive nature of ii. r fill, replenishment, dissipation aesthetic integrity of this method makes he beaches of ii. t re-nourishment and the beach it expensive Banjul and Kololi in beach feeding Gambi iii. Saly, Senegal 3.2.2 NbS Dune construction/ i. r estore natural or i. reduces both  ot appropriate for ii. n i. Nouakchott, rehabilitation: artificial dunes from coastal erosion and places with high Diawling — creating structures to a more impaired flooding in adjacent wave energy Mauritania mimic the functioning to a less impaired coastal lowlands. ii. Saint Louis, Sénégal of natural dunes state of overall function 3.2.3 NbS Wetland and i. w  ater quality and  an be re- i. c  igh soil salinity can i. h sland of Djirnda in i. I mangrove climate regulation established while make the approach Saloum Senegal restoration: maintaining the disappointing ii. accumulation sites  agué Sharif in Sine ii. G rehabilitation of present coastline for sediment carbon  limate change ii. c (Senegal) previously existing position through and nutrients may affect the wetland functions from vegetative iii. Benin approach a more impaired to a iii. provide vital transplants from less impaired state of breeding and healthy marshes overall function nursery ground for a  an reduce or ii. c variety of birds, fish even reverse and mammals wetland loss as a result of coastal development iii. relatively cheap 75 “NbS” if Coastal Where applied Ref. in compliant management Characteristics Advantages Disadvantages in West Africa text with NbS practice and (examples) principles definition 3.2.4 NbS Fluvial sediment i. encompasses a i. minimises coastal i. requires highly management: holistic holistic view of a erosion and land specialised management of whole river basin subsidence expertise and sediment supply from and downstream collaboration ii. maintain fertile rivers to the coast, coastline to find between range of lands, often in delta taking the full range of best means to different institutions areas for agricultural human activities at river manage fluvial purposes basin level into account sediment 3.3.1 NbS Early warning  ublic to be warned i. p i. easy and feasible i. in periods i. Accra, Ghana systems and flood at the same time of sounding  an provide critical ii. c ii. Lagos, Nigeria warning system: so that actions can alert, good information to to alert or inform be taken to reduce communicators are iii. Saly, Senegal protect property communities or adverse effects of needed to prevent and save lives particular coastal areas the event panic relatively low-cost of impending flood or ii. requires regular expected flood collection of local rainfall, stream level, and streamflow data  arnings are more iii. w severe, and issued if widespread flooding is expected across a large region, or flooding is imminent equires attention iv. r to three basic factors: data collection via gauging, data processing, and hardware and software 3.3.2 Flood regulation i. c  ombines existing ii. control and i. d  ams are expensive  eta … Elmina - i. K through operation of infrastructures reduction of to construct Ghana hydraulic structures: (generally built for extreme flood  ams are not ii. d ii. Togo Assuming that dams other purposes), dams can be iii.  designed for this and gates were in meteo-hydro used to generate purpose but for place upstream, it information system hydroelectric power generating hydro- appears that good and early decision power and for management of these capacity iv. reservoirs behind insuring minimum existing infrastructure dams may be water levels in can help to control source of water dry season. It is flood peak over time in for drinking and difficult to prevent the downstream area irrigation supplementary flood towards the estuary occurring at the end of the rainy season, transportation of sediments which can change landforms (e.g. deltas), and habitats failure in the system iii.  may result in serious flooding leading to death and damage to properties downstream 3.3.3 NbS Groundwater i. monitoring and  ffective surface i. e i. high data i. Elmina, Ghana management: assessment of water management requirement ii. Port of Lomé, Togo range of measures groundwater flood management ii.  to ensure sustainable conditions and groundwater direct management  lternative water iii. a availability, limit interventions supplies saltwater intrusion and limit land subsidence  ustainable iv. s groundwater supply v. ensure consistency and quality of supply whilst taking hydrological changes into account in due course 76 “NbS” if Coastal Where applied Ref. in compliant management Characteristics Advantages Disadvantages in West Africa text with NbS practice and (examples) principles definition 3.3.4 NbS Risk mapping/ flood i. e  xercise to define  elps in planning i. h  ata collection may i. d  ower Mono River i. L risk mapping: to coastal areas at risk of a more effective be expensive Basin, Togo reduce the impact of of flooding under emergency  eeds to be ii. n coastal flooding extreme conditions response integrated into such as the number ii. support planning other procedures to of houses or and development achieve reduction in businesses away from flood risk flood risk  IS frequently used ii. G zones. to produce flood maps 3.3.5 NbS Coastal setbacks: i. m  ay dictate a  rovides a buffer i. p  ver time, rising sea i. o  ufisque, Diokoul – i. R prescribed distance minimum distance between a hazard levels will reduce Sénégal to a coastal feature from the shoreline area and coastal the size of the buffer ii. Keta, Ghana such as the line of for new buildings development zone between permanent vegetation, structures and the  ay state a ii. m ii. prevents/reduces within which all or sea minimum elevation property damage certain types of above sea level for esidual risk will ii. r development are iii. preserve natural development remain prohibited shoreline dynamics  levation setbacks: iii. e iv. maintain shoreline flooding access iv. lateral setbacks: erosion v. Setback distances are determined either as fixed setback and floating setback 3.3.6 NbS Managed i. acceptance that  ighly effective at i. h i. costly realignment: the natural erosion attenuating wave  ot an option that ii. n deliberate process of processes are energy can be applied in altering flood defences best left alone, and ii. robust against any location to allow flooding of a human intervention unexpected climate defended area can allow this to requires land to be iii.  change in future continue, removing yielded to the sea and generally the infrastructure at enhances resilience likely to be highly iv.  risk from erosion or to unexpected disruptive and flooding change expensive  etting back the ii. s iii. contributes toward conflict between the v.  line of actively the restoration of need for wetland maintained intertidal habitats, creation and the defences to a consequently need to retain new line, inland promotes recreation valuable agricultural of the original or and ecotourism and historical sites preferably, to rising ground iv. maintain water approach is still vi.  quality and avoid relatively new and saltwater intrusion uncertainties still exist not possible to vii.  estimate cost in the developing world, yet to be applied in these areas 3.3.7 NbS Flood proofing  esigned to reduce i. d i. more cost effective  ry flood-proofing i. d and sheltering: the impacts of is not aesthetically  et flood-proofing ii. w elevating structures coastal flooding on pleasing allows internal and above the floodplain, structures external hydrostatic ii. requires consistent employing designs wo types: wet ii. t pressures to maintenance and building materials, and dry equalise that make structures if dry flood-proofing iii.  more resilient to design loads are flood damage, and exceeded, walls preventing floodwater may collapse, floors from entering buckle and homes structures in the flood float zone, amongst other measures 77 “NbS” if Coastal Where applied Ref. in compliant management Characteristics Advantages Disadvantages in West Africa text with NbS practice and (examples) principles definition 3.3.8 NbS Coastal zoning: i. r equires a high level i. manage multiple  reat effort i. g i. Keta project, Ghana land use system for of coordination and use of the same is required to  ko Atlantic City, ii. E regulating development public participation coastal area to overcome a Nigeria activities by dividing benefit all users varied coastal egulated at different ii. r coastal areas into zone perspective administrative levels ii. protect natural designated zones with from a variety of coastal areas and different purposes and stakeholders nursing grounds for restrictions marine fisheries iii. allows some level of economic and recreational activities iv. maintain local coastal livelihoods 3.3.9 NbS Floating agricultural i. a  imed at adapting i. c  reate areas of  nclear how it may i. u management: utilising to more regular or land suitable for be affected by areas waterlogged for prolonged flooding agriculture within rising sea levels and long periods of time in waterlogged regions increase in salinity  mploys beds of ii. e the production of food rotting vegetation,  apacity to provide ii. c which act as employment compost for crop opportunities within growth communities beds are able to iii.  iii. improvements in float on water gender equity surface 3.3.10 NbS Non-intervention/Do  ccurs in areas i. o i. relatively cheaper i. requires more nothing: not dealing where there are no and environmentally research before with the effects of inhabitants, and so friendly decision making flooding and erosion as nothing of economic it occurs or institutional value needs to be protected 78 REFERENCES Adam, P. (2019). Salt Marsh Restoration. In G. M. E. Perillo, E. Wolanski, D. R. Cahoon and C. S. Hopkinson (Eds.), Coastal Wetlands (pp. 44): Elsevier. Agency, U.S.F.E.M. (1997). Multi-Hazard Identification and Risk Assessment. Federal Emergency Management Agency. Allersma, E., Tilmans, W. M. K. (1993). Coastal conditions in West Africa - a review. Journal of Ocean and Coastal Management 19: 199- 240. Almar, R., Kestenare, E. and Boucharel, J. (2019). On the Key Influence of Remote Climate Variability from Tropical Cyclones, North and South Atlantic Mid-Latitude Storms on the Senegalese Coast (West Africa). Environmental Research Communications 1, no. 7. Almar, R., Kestenare, E., Reyns, J., Jouanno, J., Anthony, E. J., Laibi, R., et al. (2015). Response of the Bight of Benin (Gulf of Guinea, West Africa) coastline to anthropogenic and natural forcing, Part1: Wave climate variability and impacts on the longshore sediment transport. Continental Shelf Research, 110, 48–59. Almar, R., Du Penhoat, Y., Honkonnou, N., Castelle, B., Laïbi, R., Anthony, E., Senechal N., Degbe, G., Chuchla, R., Sohou, Z., Dorel, M. (2014) The Grand Popo experiment, Benin. J Coast Res 70(SI):651-656 Alves, B., Angnuureng, D.B., Morand, P. et Almar R. (2020): A review on coastal erosion and flooding risks and best management practices in West Africa: what has been done and should be done. J Coast Conserv 24, 38 (2020). https://doi.org/10.1007/s11852-020-00755-7 Amoako, C. and Boamah, E. F. (2015). The three-dimensional causes of flooding in Accra, Ghana. International Journal of Urban Sustainable Development, 7(1), 109-129. doi:10.1080/19463138.2014.984720 Amponsah, S. K., Danson, P. O., Nunoo, F. K. E., & Lamptey, A. M. (2015). Assessment of security of coastal fishing in Ghana from the perspectives of safety, poverty and catches (Master’s thesis).University of Ghana, Accra, Ghana. Anderson, I. (1991). Land reclamation poisons coastal waters. New Scientist, 1797, p 11. Angnuureng, D.B., Jayson-Quashigah, P-N., Almar, R., Stieglitz, T.C., Anthony, E.J, Aheto, DW, Appeaning Addo, K (2020) Application of Shore-Based Video and Unmanned Aerial Vehicles (Drones): Complementary Tools for Beach Studies. Remote Sens 12:394-413 Angnuureng, D.B., Appeaning, A.K., Wiafe, G. (2013) Impact of Sea Defense Structures on Downdrift Coasts: The Case of Keta in Ghana. Acad. J. Environ. Sci. 1(6):104-21 Anim, D. O., Nkrumah, P. N., & David, N. M. (2013). A rapid overview of coastal erosion in Ghana. International Journal of Scientific & Engineering Research, 4(2), 1–7. Anthony, E. J., Brunier, G., Besset, M., Goichot, M., Dussouillez, P. and Nguyen, V. L. (2015). Linking rapid erosion of the Mekong River delta to human activities. Scientific Reports, 5. Anthony, E. J. (2015). Patterns of sand spit development and their management implications on deltaic, drift-aligned coasts: The cases of the Senegal and Volta River delta spits, West Africa. In G. Randazzo, D. Jackson and Cooper, A. (Eds.), Sand and gravel spits (pp. 21–36). Heidelberg, Germany: Springer Anthony, EJ (2006) The muddy tropical coast of West Africa from Sierra Leone to Guinea-Bissau: geological heritage, geomorphology and sediment dynamics. Africa Geoscience Review 13:227-237 Anthony, E.J. (2004) Sediment dynamics and morphological stability of an estuarine mangrove complex: Sherbro Bay, West Africa. Mar Geol 208:207-224 Anthony, E. J. and Blivi, A. (1999). Morphosedimentary evolution of a delta-sourced, drift-aligned sand barrier-lagoon complex, western Bight of Benin. Marine Geology 158:161–176. Anthony, E.J. (1995) Beach-ridge development and sediment supply: examples from West Africa. Mar Geo 129:175-186 Anthony, E.J. (1989) Chenier plain development in northern Sierra Leone, West Africa. Mar Geo 90:297-309 APEIS and RIPSO (2004). Floating Agriculture in the flood-pr one or submerged areas in Bangladesh (Southern regions of Bangladesh). Bangladesh: APEIS and RIPSO. Available from http://enviroscope.iges.or.jp/ contents/APEIS/RISPO/inventory/db/pdf/0146.pdf. Appeaning Addo, K., Nicholls, R. J., Codjoe, S. N. A.and Abu, M. (2018). A biophysical and socioeconomic review of the Volta Delta, Ghana. Journal of Coastal Research. Appeaning Addo, K. (2015). Monitoring sea level rise-induced hazards along the coast of Accra in Ghana. Natural Hazards, 78(2), 1293– 1307. Appelquist, L. R., et al. (2016). Managing climate change hazards in coastal areas: The Coastal Hazard Wheel decision support system: 48. Awadzi, T. W., Ahiabor, E., & Breuning-Madsen, H. (2008). The soil-land use system in a sand spit area in the semi-arid coastal savanna region of Ghana: Development, sustainability and threats. West African Journal of Ecology, 13, 132–143. Awosika, L. F., Ibe, A. C. and Ibe, C. E. (1993). Anthropogenic activities affecting sediment load balance along the West African coastline. In: Coastlines of West Africa. L. Awosika, C. Ibe and P. Schroder (Eds.). New York: American Association of Civil Engineers 79 Balaguer, P., Sarda, R., Ruiz, M., Diedrich, A., Vizoso, G. and Tintore, J. (2008). A proposal for boundary delimitation for integrated coastal zone management initiatives. Ocean & Coastal Management, 51(12), 806-814. Barends., F. B. J (2003). Groundwater mechanics in flood risk management in Kono I, Nishigaki M and Komatsu M (eds.). Groundwater Engineering: Recent Advances. Rotterdam: A.A. Balkema, 53- 66. Barusseau, J. P., Cyr Descamps, M.B., Salif Diop, E., Diouf, B. Kane, A., Saos, J.-L., and Soumaré, A. ( 1 9 9 8 ) . Morphological and sedimentological changes in the Senegal River estuary after the construction of the Diama dam. Journal of African Earth Sciences 26 (2): 317-326. Barusseau, P. , Brigand, L., Denis, J., Gerard, B., Grignon-Logerot, C., Henocque, Y. (1997). Methodological guide to ICZM. UNESCO Intergovernmental Ocean Commission, Paris Barusseau, J. P. (1980). Essai d'évaluation des transports littoraux sableux sous l'action des houles entre Saint-Louis et Joal (Sénégal). Bulletin Asequa, Dakar 58-59, 31-39. Bevacqua, A., Yu, D. and Zhang, Y. (2018). Coastal Vulnerability: Evolving Concepts in Understanding Vulnerable People and Places. Environmental Science & Policy 82: 19-29. Berkes, F., & Folke, C. (1998). Linking social and ecological systems for resilience and sustainability. Linking social and ecological systems: management practices and social mechanisms for building resilience, 1(4), 4. *Bird E (2005). Appendix 5: Glossary of Coastal Geomorphology in Schwartz, M.L. (ed.). Bird, E.C. F. (1996). Beach management. John Wiley & Sons Ltd. Chichester. Encyclopedia of Coastal Science. The Netherlands: Springer, 1155- 1192. Blaikie, P., Cannon, T., Davis, I. and Wisner, B. (2014). At Risk: Natural Hazards, People’s Vulnerability and Disasters. Routledge: London Blivi, A., Anthony, E. J., Oyédé, LM (2002) Sand barrier development in the Bight of Benin, West Africa. Ocean and Coastal Management 45:185-200 Blivi, A. (1993). Morphology and current dynamic of the coast of Togo. Geo-Eco-Trop 17(1-4), 21- 35. Boateng, I. (2012). An application of GIS and coastal geomorphology for large scale assessment of coastal erosion and management: a case study of Ghana. Journal of Coastal Conservation 16:383- 397. Boateng, I., Bray, M. and Hooke, J. (2011). Estimating the fluvial sediment input to the coastal sediment budget: A case study of Ghana, Geomorphology 138, 100-110. Boateng, I. (2009). Development of integrated shoreline management planning: A case study of Keta. Federation of International Surveyors Working Week. Eilat, Israel. Available from: https://www.fig.net/resources/proceedings/fig_ proceedings/fig2009/papers/ts04e/ts04e_boateng_346 3.pdf. Bollen, M., Trouw, K., Lerouge, F., Gruwez, V., Bolle, A., Hoffman, B., et al. (2011). Design of a coastal protection scheme for Ada at the Volta River mouth (Ghana). Proceedings of 32nd Conference on Coastal Engineering, 2010. Shanghai, China. International Conference on Coastal Engineering (ICCE). Brampton A (2002). ICE Design and Practice Guides: Coastal Defence. London: Thomas Telford. Bromfield, T. (2006). Available from http://www.geographical. co.uk/Magazine/Atlantic_rising_-_Sep_10.html Burgess K., Jay, H. and Nicholls R. J. (2007). Drivers of coastal erosion in Thorne CR, Evans EP and PenningRowsell, EC (eds.). Future Flooding and Coastal Erosion Risks. London: Thomas Telford, 267-279. Cambers, G. (1998). Planning for Coastline Change: Coastal Development Setback Guidelines in Antigua and Barbuda. Paris: UNESCO. Available from http://tiny.cc/j5va7. Celliers, L. and Ntombela, C. (2015). Urbanisation, coastal development and vulnerability, and catchments. In: UNEP- Nairobi Convention and WIOMSA. The Regional State of the Coast Report: Western Indian Ocean. UNEP and WIOMSA, Nairobi, p. 387-406 Charlier, R. and de Meyer, C. P. (1998). Coastal Erosion: response and management. pp. 194-222. Heidelberg and New York: Springer Verlag. Cohen-Shacham, E.,Walters, G., Janzen, C., Maginnis, S. (2016). Nature-based solutions to address societal challenges. Gland, Switzerland: International Union for Conservation of Nature Cohen-Shacham, E., Andrade, A., Dalton, J., Dudley, N., Jones, M., Kumar, C., Maginnis, S., Maynard, S., Nelson, C. R. , Renaud, F. G., Welling, R. and Walters, G. (2019) Core Principles for Successfully Implementing and Upscaling Nature- Based Solutions. Environmental Science & Policy 98: 20-29. Collins, S. L., Carpenter, S. R., Swinton, S. M., Orenstein, D. E., Childers, D. L., Gragson, T. L., ... & Knapp, A. K. (2011). An integrated conceptual framework for long‐term social–ecological research. Frontiers in Ecology and the Environment, 9(6), 351-357. Cormier-Salem, M. C., & Panfili, J. (2016). Mangrove reforestation: greening or grabbing coastal zones and deltas? Case studies in Senegal. African journal of aquatic science, 41(1), 89-98. 80 Cutter, S. L., Mitchell, J. and Scott, M. S. (2000). Revealing the vulnerability of people and places: a case study of Georgetown County, South Carolina.Annals of the American Association of Geographers 90(4):713-737. Carrero, R., Navas, F., Malvárez, G., & Cáceres, F. (2013). Participative future scenarios for integrated coastal zone management. Journal of Coastal Research, 65(sp1), 898-903. Cicin-Sain, B., Knecht, R. W., Jang, D., Knecht, R., & Fisk, G. W. (1998). Integrated coastal and ocean management: concepts and practices. Island press. Cutter, S. L., Boruff, B. J. and Shirley, W. L. (2003). Social vulnerability to environmental hazards. Social Science Quarterly 84(2):242-261. Danquah, J. A., Attippoe, J. A., and Ankrah, J. S. (2014). Assessment of residential satisfaction in the resettlement towns of the Keta Basin in Ghana. International Journal of Civil Engineering, Construction and Estate Management, 2(3), 26–45. Davis Jr, R. A. and Fitzgerald, D. M. (2004). Beaches and Coasts. Massachusetts: Blackwell Publishing. D’Ercole, R. avec la collaboration de Thouret J.-C., Dollfus O., Astré J.-P.(1994).“Les vulnérabilités des sociétés et des espaces urbanisés: concepts, typologie, modes d’analyse”. Revue de géographie alpine, 82(4), 87-96.DHI (2015). Water Resources Modelling. Available from: http://www.dhigroup.com/upload/publications/ brochures/waterresourcesmodelling. pdf Dublin-Green C.O., Awosika, L.F. and Folorunsho, R. (1999). Climate Variability Research Activities in Nigeria. Nigerian Institute for Oceanography and Marine Research, Victoria Island, Lagos, Nigeria. Dumas, D., Mietton, M., Hamerlynck, O., Pesneaud, F., Kane, A., Coly, A. and Baba, M. L. O. (2010). Large dams and uncertainties. The case of the Senegal River (West Africa). Society & Natural Resources 23(11): 15. Eakin, H., & Luers, A. L. (2006). Assessing the vulnerability of social-environmental systems. Annu. Rev. Environ. Resour., 31, 365-394. FAO (1995). Code of Conduct for Responsible Fisheries. Rome. 41 pp. Available from http://www.fao.org/3/v9878e/ v9878e00.htm Faye B., Dome T., Ndiaye D., Diop Ch., Faye G. and Ndiaye A. (2019). Évolution des terres salées dans le nord de l’estuaire du Saloum (Sénégal), Géomorphologie: relief, processus, environnement, vol.25 - n°2 | 2019, 81-90. Faye, B (2010) Coastline Dynamics on Sandy Littorals from Mauritania to Guinea-Bissau (West Africa): Regional and Local Approach through Photo-Interpretation, Image Processing, and Ancient Maps Analysis. PhD Thesis, University of Brest. FEMA (Federal Emergency Management Agency) (2009). Homeowner’s Guide to Retrofitting. Washington DC: Dept. of Homeland Security. Available from http://tiny.cc/kfnxq http://www.fema.gov/hazard/map/firm. shtm -1. FEMA (Federal Emergency Management Agency) (2008). Floodplain Management Bulletin: Historic Structures. Washington DC: US Dept. of Homeland Security. FEMA (Federal Emergency Management Agency) (2007). Selecting Appropriate Mitigation Measures for Floodprone Structures. Washington DC: US Dept. of Homeland Security. Available from www.fema.gov/library/viewRecord.do?id=2737. Fenster MS (2005). Setbacks, in Schwartz ML (ed.). Encyclopedia of Coastal Science. The Netherlands: Springer, 863-866. Finkl, C. W. and Walker, H. J. (2005). Beach nourishment. In: M. L. Schwartz (Ed.), The Encyclopedia of Coastal Science. pp. 37-54. Dordrecht: Kluwer Academic. Fischborn, M. and Herr, D. (2015). African solutions in a rapidly changing world: nature-based solutions to climate change by african innovators in protected areas. Gland: IUCN. 36pp Frazier, T. G., Thompson, C. M., & Dezzani, R. J. (2014). A framework for the development of the SERV model: A Spatially Explicit Resilience-Vulnerability model. Applied Geography, 51, 158- 172. French, P. W. (2001). Coastal defences: processes, problems and solutions. Routledge: London French, P. W. (1997). Coastal and Estuarine Management. Routledge: London. Gallopín, G. C. (2006). Linkages between vulnerability, resilience, and adaptive capacity. Global environmental change, 16(3), 293-303. Gampson, E. K., Nartey, V. K., Golow, A. A., Akiti, T. T., Sarfo, M. A., Salifu, M., et al. (2017). Physical and isotopic characteristics in peri-urban landscapes: A case study at the lower Volta River Basin. Ghana. Applied Water Science, 7(2), 729–744. Giardino, A., Schrijvershof, R., Nederhoff, C.M., de Vroeg, H., Brière, C., Tonnon, P.K., Caires, S., Walstra, D.J., Sosa, J., van Verseveld, W., Schellekens, J., Sloff. C.J. (2018) A Quantitative Assessment of Human Interventions and Climate Change on the West African Sediment Budget. Ocean Coast Manag 156: 249-65 Glasser, M. and Farvacque-Vitkovic, C. (2008). Africa's urbanization for development: understanding Africa's urban challenges and opportunities. Washington, DC: World Bank. Available from: http://documents.worldbank.org/curated/ en/599241468002680246/Africas-urbanization-for- development-understanding-Africas-urban-challenges-and- opportunities 81 Godschalk, D. R., Brody, S. and Burby, R. (2003). Public Participation in Natural Hazard Mitigation Policy Formation: Challenges for Comprehensive Planning. Journal of Environmental Planning and Management 46(5):733-54. Goussard, J. J., & Ducrocq, M. (2017). Facing the future: Conservation as a precursor for building coastal territorial cohesion and resilience. Aquatic Conservation: Marine and Freshwater Ecosystems, 27, 151-161. https://doi.org/10.1002/ aqc.2823 Hansom, J. D. and McGlashan, D. J. (2000). Impacts of bank protection on Loch Lomond Scottish Natural Heritage, Research, Survey & Monitoring Report No. 154 Haq AHMR, Ghosal TK and Ghosh P (2004). Cultivating wetlands in Bangladesh. India: LEISA. Available from http://bit. ly/c3Ah0o. Healy, T.R. and Dean, R.G. (2000). Methodology for delineation of coastal hazard zones and development setback for open duned coasts in Herbich JB (ed.). Handbook of Coastal Engineering. New York: McGraw-Hill, Chapter 19. Hewawasam, I. (2002). Managing the marine and coastal environment of Sub-Saharan Africa. Directions in Development. Washington, DC; World Bank Group. Available from http://documents.worldbank.org/curated/en/622841468004845659/ Managing-the-marine-and- coastal-environment-of-Sub-Saharan-Africa Hillen, M.M., Jonkman, S.N., Kanning, W., Kok, M., Geldenhuys, M., Vrijling, J.K. and Stive, M.J.F. (2010). Coastal Defence Cost Estimates. Case Study of the Netherlands, New Orleans and Vietnam. The Netherlands: TU Delft. Available from http://tiny.cc/lwlkh. Hillen, M.M. (2008). Safety Standards Project, Risk Analysis for New Sea Dike Design Guidelines in Vietnam. Technical Report Delft University of Technology / Hanoi Water Resources University; Sea Dike Project. IFRC (2015). Emergency Plan of Action (EPoA) Ghana: Floods. Available from http://reliefweb.int/sites/reliefweb.int/files/ resources/MDRGH011.pdf IFRC (2012). Emergency appeal operation Nigeria: Floods. Available from http://reliefweb.int/report/nigeria/nigeria-floods- emergency-appeal-n%C2%B0-mdrng014-operation-update-n%C2%B01 Ibe, AC (1988) Coastline Erosion in Nigeria. Ibadan University Press, Ibadan Nigeria. Ile, I. U., Garr, E. Q., and Ukpere, W. I. (2014). Monitoring infrastructure policy reforms and rural poverty reduction in Ghana: The case of Keta Sea Defence Project. Mediterranean Journal of Social Sciences, 5(3), 633. IOC (2009) Hazard Awareness and Risk Mitigation in Integrated Coastal Area Management (ICAM). Intergovernmental Oceanographic Commission (IOC) Manual and Guides No 50, ICAM Dossier No 5. Paris: UNESCO. Kane, C., Humbert, J., and Kane, A. (2013). Responding to climate variability: the opening of an artificial mouth on the Senegal River. Regional environmental change, 13(1), 125-136. Kasperson, R. E., Dow, K., Archer, E., Cáceres, D. M., Downing, T., Elmqvist, T., Eriksen, S., Folke, C., Han, G., Iyengar, K., Vogel, C., Wilson, K. and Ziervogel, G. (2005). Vulnerable peoples and places. In R. Hassan, R. Scholes and N. Ash (Eds.), Ecosystems and human well-being: Current state and trends findings of the condition and trends working group. Volume 1, pp. 146-162. Washington: Island Press. Kates, R. W. (1985). The interaction of climate and society. In: R. W. Kates, J. H. Ausubel and M. Berberian (Eds.), Climate Impact Assessment SCOPE 27. pp. 3-36. New York: Wiley. Kay, R. (1990). Development controls on eroding coastlines: Reducing the future impact of greenhouse-induced sea level rise. Land Use Policy, 7 (4), 169-172. Koch, E. W., Barbier, E. B., Silliman, B. R., Reed, D. J., Perillo, G. M., Hacker, S. D., ... & Halpern, B. S. (2009). Non‐linearity in ecosystem services: temporal and spatial variability in coastal protection. Frontiers in Ecology and the Environment, 7(1), 29-37. Komar, P. D. (1998). Beach processes and sedimentation Prentice Hall, Englewood Cliffs NJ Kortatsi, B. K., Young, E., & Mensah-Bonsu, A. (2005). Potential impact of large scale abstraction on the quality of shallow groundwater for irrigation in the Keta Strip, Ghana. West African Journal of Applied Ecology, 8, 1. Kraus, N. C. and MacDougal, W. G. (1996). The effects of seawalls on the beach: part 1 an updated literature review Journal of Coastal Research 12:691–701. Kraus, N. C. and Pilkey, O. H. (1988). The effects of seawalls on the beach Journal of Coastal Research 4(SI). Kristensen, S. E., Drønen, N., Deigaard, R. and Fredsoe, J. (2016). Impact of groyne fields on the littoral drift: A hybrid morphological modelling study. Coastal Engineering 111: 13-22. Kumapley, N. K. (1989). The geology and geotechnology of the Keta basin with particular reference to coastal protection. In W. J. M. van der Linden, S. A. P. L. Cloetingh, J. P. K. Kaasschieter, W. J. E. van de Graaff, J. Vandenberghe, & J. A. M. van der Gun (Eds.), Coastal lowlands: Geology and geotechnology (pp. 311–320). Dordrecht, The Netherlands: Springer. 82 Laïbi, R.A., Anthony, E.J., Almar, R., Castelle, B., Sénéchal, N., Kestenare, E. (2014) Longshore drift cell development on the human-impacted Bight of Benin sand barrier coast, West Africa. J Coast Res 70(SI): 78-83 Leggett, D. J., Cooper, N. and Harvey, R. (2004). Coastal and Estuarine Managed Realignment – Design Issues. London: CIRIA. Linham M.M., Green, C.H. and Nicholls, R.J. (2010). AVOID Report on the Costs of adaptation to the effects of climate change in the world’s large port cities. Folorunsho, A. R. (2004). Environmental Consequences of Meteorological Factors Affecting Ocean Dynamics along Gulf of Guinea Coast. Unpublished PhD thesis, University of Lagos, Nigeria. Ly, C. K. (1980). The role of the Akosombo dam on the Volta River in causing coastal erosion in Central and Eastern Ghana (West Africa). Marine Geology 37: 323–32 McGlashan, D. J. and Fisher, G. R. (2000). The legal and geomorphic impacts of engineering decisions on integrated coastal management in Fleming C A ed Coastal management: integrating science, engineering and management Thomas Telford, London 137–46 Mcglashan, D. J. (2003). Managed relocation: an assessment of its feasibility as a coastal management option. The Geographical Journal 169(1): 6-20. Manson, A. A. B., Appeaning Addo, K., and Mensah, A. (2013). Impacts of shoreline morphological change and sea level rise on mangroves: The case of the Keta coastal zone. E3 Journal of Environmental Research and Management, 40(10), 0334–0343. Martin, L. (1971). The continental margin from Cape Palmas to Lagos: bottom sediments and submarine morphology. Institute of Geological Science Report 70/16:79–95. Masselink, G. and Hughes, M. G. (2003). Introduction to Coastal Processes and Geomorphology. London: Arnold. Mathews, E. R. (1934). Coast erosion and protection. London: Charles Griffin & Company. Meur-Férec, C., Deboudt, P., & Morel, V. (2008). Coastal risks in France: an integrated method for evaluating vulnerability. Journal of Coastal Research, (24), 178-189. Mileti, D. (1999). Disasters by Design: A Reassessment of Natural Hazards in the United States. Washington: Joseph Henry Press Milliman J. D. and Mei-e, R. (1995). River flux to the sea: Impact of human intervention on river systems and adjacent coastal areas, In Climate Change Impact on Coastal Habitation / editor D. Eisma, CRC Press. Monteillet, J. (1986). Environnements sédimentaires et paléoécologie du delta du Sénégal au Quaternaire. 267p. lmprimerie des Tilleuls, Millau. Myatt-Bell, L. B., Scrimshaw, M. D., Lester, J. N. and Potts, J. S. (2002). Public perception of managed realignment: Brancaster West Marsh, North Norfolk, UK Marine Policy 26 45–57 Ndour, A,. Laïbi, R.A., Sadio, M., Degbe, C., Degbe, E., Diaw, A.T., Oyede, L., Anthony, E.J., Dussouillez, P., Sambou, H., Dieye, E.B. (2017) Management strategies for coastal erosion problems in west Africa: Analysis, issues, and constraints drawn from the examples of Senegal and Benin. Ocean Coast Manage 156:92-106 Nairn, R. B., and Dibajnia, M. (2004). Design and construction of a large headland system, Keta Sea Defence Project, West Africa. Journal of Coastal Research, 33, 294–314. Special Issue. Nairn, R. B., MacIntosh, K. J., Hayes, M. O., Nai, G., Anthonio, S. L., and Valley, W. S. (1999). Coastal erosion at Keta Lagoon, Ghana: Large scale solution to a large scale problem. Proceedings of the 26th Conference on Coastal Engineering 1998, June 22–26, Copenhagen, Denmark. American Society of Civil Engineers. Nicholls, R.J., Cooper, N. and Townend, I.H. (2007). The management of coastal flooding and erosion in C. R. Thorne et al. (Eds.). Future Flood and Coastal Erosion Risks. Thomas Telford, London, pp. 392-413. Nobre, A. M. (2011). Scientific approaches to address challenges in coastal management. Marine Ecology Progress Series 434:279-289. Nordstrom, K. F. (2000). Beaches and dunes of developed coasts Cambridge University Press, Cambridge Ntajal, J., Lamptey, B., Mahamadou, I. B., Nyarko, B. K. (2017). Flood disaster risk mapping in the Lower Mono River Basin in Togo, West Africa. International Journal of Disaster Risk Reduction, 23, 93–103. Oguntunde, P. G., Friesen, J., van de Giesen, N., and Savenije, H. H. G. (2006). Hydroclimatology of the Volta River Basin in West Africa: Trends and variability from 1901 to 2002. Physics and Chemistry of the Earth, Parts A/B/C, 31(18), 1180–1188. Olsen, S. B. (2003). Frameworks and indicators for assessing progress in integrated coastal management initiatives. Ocean & coastal management, 46(3-4), 347-361. 83 Opoku-Agyemang, M. (2001). Water Resources Commission Act and the nationalisation of water rights in Ghana. Proceedings of ‘Securing the future: International Conference on Mining and the Environment’, Skellefteå, Sweden. The Swedish Mining Association. Oteng-Ababio, M., Owusu, K., and Appeaning Addo, K. (2011). The vulnerabilities of the Ghana coast: The case of Faana- Bortianor. JAMBA: Journal of Disaster Risk Studies, 3(2), 429–442. Ouikotan, R. B, van der Kwast, J., Mynett, A., Afouda, A. (2017). Gaps and challenges of flood risk management in West African coastal cities. Available from https://iwra.org/member/congress/resource/ABSID329_ABSID329_full_paper.pdf Owens, J. S. and Case, G. O. (1908). Coast erosion and foreshore protection St Bride’s Press, London. Ozer, P., Hountondji, Y.C., de Longueville, F. (2017) Evolution récente du trait de côte dans le golfe du Bénin. Exemples du Togo et du Bénin. Geo-Eco-Trop 41(3):529-541. Padmalal, D., Maya, K., Sreebha, S., & Sreeja, R. (2008). Environmental effects of river sand mining: a case from the river catchments of Vembanad lake, Southwest coast of India. Environmental geology, 54(4), 879-889. Parliamentary Office of Science and Technology. (2009). Postnote: Coastal Management. London: Parliamentary Office of Science and Technology. Available from www.parliament.uk/documents/post/postpn342.pdf Philpot, K. L. (1984). Cohesive coastal processes. Engineering Institution of Canada Annual Conference. Preston, B. L., Yuen, E., Westway, R. M. (2011). Putting vulnerability to climate change on the map: a review of approaches, benefits, and risks. Sustainable Science 6(2):177–202. Post, J. C. and Lundin, C. G. (1996). Guidelines for Integrated Coastal Zone Management. Washington, D.C.: The World Bank. Available from http://documents.worldbank.org/curated/en/754341468767367444/Guidelines-for-Integrated- Coastal-Zone-Management Pontee, N., Narayan, S., Beck, M. W. and Hosking, A. (2016). Nature-based solutions: Lessons from around the world. Maritime Engineering 169(1):29-36. Psuty, N. P. and Moreira, M. E. S. A. (1990). Nourishment of a cliffed coastline, Praia da Rocha, the Algarve, Portugal. Journal of Coastal Research 6(SI): 21–32. Reuters, T. (2008). Whitepaper using bibliometrics: a guide to evaluating research performance with citation data. Available from http://ips.clarivate.com//m/pdfs/325133_thomson.pdf Rossi, G. (1989) L’érosion du littoral dans le Golfe du Bénin : un exemple de perturbation d’un équilibre morphodynamique. Zeitschrift für Geomorphologie 73:139-165. Rupp-Armstrong, S. and Nicholls, R. (2007). Managed realignment and regulated tidal exchange – implications for coastal habitat adaptation in the European Union. Journal of Coastal Research. Sadio, M., Anthony, E.J., Diaw, A.T., Dussouillez, P. Fleury, J.T., Kane, A., Almar, R., Kestenare, E. (2017) Shoreline changes on the wave-influenced Senegal River delta, West Africa: The roles of natural processes and human interventions. Water 9(5): 357 https://doi.org/10.3390/w9050357 Saha SK (2010). Soilless Cultivation for Landless People: An Alternative Livelihood Practice through Indigenous Hydroponic Agriculture in Flood-prone Bangladesh. Beppu: Ritsumeikan Asia Pacific University. Available from http://tiny.cc/8ncx1. Salloum, A. A., Al-Emran, M., Monem, A. A. and Shaalan, K. (2018). Using Text Mining Techniques for Extracting Information from Research Articles. Studies in Computational Intelligence. In book: Intelligent Natural Language Processing: Trends and Applications Sanyal, J. and Lu, X.X. (2003). Application of GIS in flood hazard mapping: a case study of Gangetic West Bengal, India. Map Asia 2003, Poster Session. Available from http://tiny.cc/r7zci. Setordzi, I., and Nyavor, G. (2015). Oil exploration to start soon in Keta in spite of challenges. Joyonline news. Available from: http://www.myjoyonline.com/news/2015/february-5th/oil- exploration-to-startsoon-in-keta-despite-challenges.php. Scott, T., Austin, M., Masselink, G. and Russell, P. (2016). Dynamics of rip currents associated with groynes — field measurements, modelling and implications for beach safety. Coastal Engineering 107: 53-69. Shennan, I. (1993). Sea-level changes and the threat of coastal inundation. Geographical Journal 159: 148–56. Silvester, R. and Hsu, J. R. C. (1993). Coastal Stabilization: Innovative Concepts. Prentice-Hall: Englewood Cliffs pp. 578 Slocombe DS (1998). Lessons from experience with ecosystem-based management. Landscape and Urban Planning. 40:31-39. Ssentongo, G.W. (1987). Marine fishery resources of Liberia: A review of exploited fish stocks. CECAF/ECAF SERIES 87/45: 79 pp. 84 Tait, J. F. and Griggs, G. B. (1990). Beach response to the presence of a seawall: a comparison of field observations. Shore and Beach 11–28 Tallis H, Levin PS, Ruckelshaus M, Lester SE, McLeod KL, Fluharty DL and Halpern BS (2010). The many faces of ecosystem-based management: Making the process work today in real places. Marine Policy. 34:340-348. TAW (2002). Technical Report. Wave run-up and wave overtopping at dykes. Technical Advisory Committee on Flood Defences, the Netherlands. Thior, M., Sané, T. Dièye, E.-H.B., Sy, O, Cissokho, D, Ba, BD, Descroix, L (2019). Coastline dynamics of the northern Lower Casamance (Senegal) and southern Gambia littoral from 1968 to 2017. Journal of African Earth Sciences 160:103611. Turner, B. L., Kasperson, R. E., Matson, P. A., McCarthy, J. J., Corell, R. W., Christensen, L., ... & Polsky, C. (2003). A framework for vulnerability analysis in sustainability science. Proceedings of the national academy of sciences, 100(14), 8074-8079. Tsidzi, K. E. N., and Kumapley, N. K. (2001). Coastal erosion in Ghana: Causes and mitigation strategies. In P. G. Marinos, G. C. Koukis, G. C. Tsiambaos, & G. C. Stournaras (Eds.), Engineering geology and the environment, volume 5 (pp. 3941–3946). Lisse, The Netherlands: A A Balkema. UEMOA, MOLOA, UICN (2010) : Etude de suivi du trait de côte et schéma directeur du littoral de l’Afrique de l’ouest (SDLAO). Prescriptions détaillées. 136 pp. Dakar. UNEP (2011): Taking Steps toward Marine and Coastal Ecosystem-Based Management- An Introductory Guide UN - Division of the Department of Economic and Social Affairs. (2018). World Urbanization Prospects. Available from : https://population.un.org/wup/UN - Habitat. (2014). The State of African Cities 2014: Re-imagining sustainable urban transitions. UN-Habitat. Nairobi, Kenya UN - Environmental Programme/Nairobi Convention Secretariat and WIOMSA (2009). Transboundary Diagnostic Analysis of Land-based Sources and Activities Affecting the Western Indian Ocean Coastal and Marine Environment. UNEP Nairobi, Kenya. UNESCO-IOC. (2012). A Guide on adaptation options for local decision-makers: guidance for decision making to cope with coastal changes in West Africa. Available from https://unesdoc.unesco.org/ark:/48223/pf0000216603 USACE (United States Army Corps of Engineers). (1989). Environmental Engineering for Coastal Shore Protection. Washington, DC: USACE. Available from https://apps.dtic.mil/dtic/tr/fulltext/u2/a402816.pdf 29/07/2019 Van der Linden, W. J. M., Cloetingh, S. A. P. L., Kaasschieter, J. P. K., Vandenberghe, J., van de Graaff, W. J. E., & van der Gun, J. A. M. (Eds.). (2013). Coastal lowlands: Geology and geotechnology. Dordrecht, The Netherlands: Springer. Vinhateiro, N., Sullivan, K. A., and Mcnally, C. G., (2012). Training for the next generation of coastal management practitioners. Journal of Coastal Research, 28(5), 1297–1302. Coconut Creek (Florida), ISSN 0749-0208. Walling, D. E. (2006). Human impact on land-ocean sediment transfer by the world’s rivers. Geomorphology 79, 192-216. Wiafe, G., Boateng, I., Appeaning Addo, K., Quashigah, P. N. J., Ababio, S. D., & Laryea, S. (2013). Handbook of coastal processes and management in Ghana. Gloucester, UK: The Choir Press. World Bank. (1996). Toward environmentally sustainable development in sub-Saharan Africa: a World Bank agenda. Development in practice. Washington, D.C.: World Bank. Available from http://documents.worldbank.org/curated/ en/690781468742823785/Toward-environmentally- sustainable-development-in-sub-Saharan-Africa-a-World-Bank- agenda World Bank. (1997). Ghana - Village Infrastructure Project. World Development Sources, WDS 1997-1. Washington, DC: World Bank. Available from: http://documents.worldbank.org/curated/en/117491468771067701/Ghana-Village- Infrastructure- Project Yim WWS (1995). Implications of Sea Level Rise for Victoria Harbour, Hong Kong. Journal of Coastal Research, Special Issue 14, 167-189. Zhu, X., Linham, M. M., and Nicholls, R. J. (2010). Technologies for Climate Change Adaptation - Coastal Erosion and Flooding. Roskilde: Danmarks Tekniske Universitet, Risø Nationallaboratoriet for Bæredygtig Energi. TNA Guidebook Series.Appendix 1: Methodological approach: bibliometric and text mining analysis 85 Benin. Photo: ONG Corde APPENDIX 1: METHODOLOGICAL APPROACH: BIBLIOMETRIC AND TEXT MINING ANALYSIS The bibliometric analysis conducted in this chapter will attempt to assess to what extent, and according to what timing, the scientific community working in West Africa has taken up the subject of coastal management and defence against erosion. More specifically, it is a question of examining the quantity and evolution dynamics through the last 25 years and comparing it to worldwide dynamics. Then, through text mining analysis of the meta-information content describing the articles in the Web of Science (WoS), it will be possible to identify the priority topics and areas addressed by researchers working in West Africa on coastal management and defence issues, and to determine to which national and international networks these researchers are bound. 1. BIBLIOMETRIC Essentially, bibliometric is the application of quantitative analysis and statistics to publications such as journal articles and estimating their accompanying citation counts (Thomson Reuters, 2008). It evaluates research performance based on citation data. Data on research performance helps university and research centres understand the institution’s position relative to global and domestic standards. The bibliometric tool helped to reveal key areas of research in relation to the issues addressed in this compendium, the quantity of research conducted in West Africa, the number faculty members’ articles published and in which journals, and determine if there is a pattern in the number of publications. In terms of current interest, a bibliometric approach helped to depict the evolution of relevant topics in a time span across 24 year [MOU2] (1995 - 2018), which provides ample time to identify the core articles considered the most successful and pertinent to the area of interest. The analysis allowed for trend analysis, i.e., showing topics trending in time series, also to ascertain the status of collaboration using indicators such as rates of co- authorship for pairs of authors, institutions, and countries. In this study, interest focused on coastal erosion, coastal flooding, salt water intrusion, rising sea leves, i.e. coastal physical processes, and methods applied to the survey as well as appropriate management. In order to retrieve scientific papers related to the domain, the authors defined a request - ‘Bibliographic Coastal Environment Request (BCER)’ which was applied on the WoS published articles database. The requested search for a combination of words (terms searched, (TS)) was in the document title, keywords list and abstract. Notice that TS may be a shortened version of the full term which can be found in the document. 86 Specification of BCER WoS request: over 1,790 scientific journals. The 25 most important journals (in terms of occurrence) cover 7,350 (TS="coast*" or TS="shoreli*" or TS="littoral*") and publications, i.e. 33.1 per cent of the total. Among the 25 most important journals (Figure 2), the Journal (TS="climat*" or TS="wave*" or TS="sea level*" or of Coastal Research is more noticable, as it alone is TS="erosi*" or TS="sediment*" or TS="accretio*" responsible for 19.31 per cent of the 7,350 published or TS="subsidenc*" or TS="drift*" or TS="flood*" or articles in the top 25 scientific journals and 6.39 per TS="salin*" or TS="salt*") cent of all published papers in 1,790 journals. and Following this method, the West Africa regional (TS="infrast*" or TS="vulnerab*" or TS="risk*" or level was analysed in order to detect articles, which TS="hazar*" or TS="exposur*" or TS="defenc*" or specifically published regional material. A filter was TS="protect*" or TS="managem*" or TS="adaptat*" used to search for the occurrence of a set of regional or TS="resilience*" or TS="relocation*" ) geographic words1 in the document title, keywords list and abstract. This led to a list of 179 publications and that mention, in one way or another, countries or (TS="breach*" or TS="spit*" or TS="mouth*" or TS="beach*" or TS="mangrov*" or TS="delta*" or TS="estuar*" or TS="marsh*" or TS="groundwater*" or TS="peninsula*" or TS="island*" or TS="community*") or (TS="harbor*" or TS="tourism*" or TR="city*" or TS="cities*" or TS="model*" or TS="GIS*" or TS="mapping*" or TS="warning*" )) This request led to 22,197 published articles worldwide. The outcome shows that the request is inclusive, as it encompasses papers related to other topics and not only papers related to the core relevant issues. The findings also suggest that, it would be difficult to omit Figure 2 - Distribution of published articles worldwide on Web of Science less relevant publications at this global stage, since it on coastal environment topics, according to the publication of the first 25 journals listed. Results of the BCER, no filter, n = 22,197. would have required reading all abstracts. The evaluation at worldwide status of publications coastal regions from West Africa. However, this concerns the evolution of the quantity of papers list is extensively broad in terms of thematic areas. between 1995 and 2018 (Fig. 1). The trend shows a For instance, it includes articles primarily focused clear growth that follows an exponential range, with on biodiversity, ecotoxicology, pollution and health an evolution ranging from n = 166 in 1995 to 523 in issues, topics that are not of interest for completing 2005, 1,798 in 2015 and finally 2,678 in 2018, which this work. shows a constant growth rate of 13 per cent per year, Since this list of regional geographic words are or more precisely an increase of 4.5 times over the consistent in terms of semantic domain, i.e. the words 2006-2018 period. At the same time, the total number share a strong core meaning related to the topic of of publications recorded on WoS also increased, but interest, the authors can apply statistical analysis on at a slower rate. the list of 179 regional documents in order to compare The second analysis (Figure 2) refers to the distribution scientific literature dealing with West Africa to the of publications in various scientific journals. The results available global literature. show a total number of 22,197 articles published by Figure 3 concerns the evolution of the number of articles between 1995 and 2018 in West Africa. The trend shows a stable period from 1995 to 2006, then a nearly linear progressive growth with an abrupt increase, ranging from n = 3 in 2006 to n = 7 in 2010, then n = 17 in 2015 and finally n = 24 in 2018, showing an eight times increase in the annual number of publications over the final 12-year period. One of the relevant findings is that the fast growth phase of publications on coastal environment in West Africa 1 Cameroun, Nigeria, Benin , Togo, Ghana, Côte d’Ivoire, Liberia, Sierra Leone, Guinee, Gambie, Senegal, Mauritanie, Cap Vert, Sao Tome, Gabon, Cameroon, Ivory Coast, Figure 1 - Distribution of published articles worldwide on the Web of Science Guinea, Gambia, Mauritania, Cape Verde, Niger, Volta, Bijagos, Banc d’Arguin, on coastal environment topics, according to the publication of the first 25 Arguin Bench, Douala, Malabo, Lagos, Cotonou, Lome, Accra, Cap Coast, Comoue, Komoe, Conakry, Freetown, Monrovia, Nouakchott, Banjul, Abidjan, Dakar, journals reported. Results of the BCER, no filter, n = 22,197. Exponential Saloum, Bandama, Sassandra, Oueme, Ogun, Sanaga, Grain coast, Sekondi, West function: Ny-1994 = 143,42 exp 0,1221 (y-1994) Africa, West-Africa, Afrique de l’Ouest, Praia, Casamance. 87 a list of 95 documents that not only address the core topic of this study but also relate to West Africa. 2. TEXT MINING ANALYSIS Text mining is a technique for extracting information from research articles (Salloum et al., 2018) and was carried out with Gargantext software (https:// Figure 3 - Trend of publications listed in Web of Science worldwide related to gargantext.org). coastal environment topics related to the West Africa region. Results of the BCER, no filter, n = 179. According to respective areas of application, text began about 10 years later than the global trend mining can be described as text categorisation, in research. However, current research shows an text clustering, association rule extraction and text increased rate higher in West African publications in visualisation. In relation to the current study, the aim comparison to the global level. is to extract interesting information from the collected Figure 4 shows the distribution of West Africa related articles (95). articles published in various scientific journals. The The questions examined by text mining analysis are results show that the total number of papers (n = 179) as follows: were published by over 108 scientific journals. The 25 most important (in terms of occurrence) scientific  hat are the most common terms (words or 1. W journals published 90 papers, i.e. 50.3 per cent of groups of words) among the articles collected the total. Among the 25 most important journals, the and what are terms have strong links (frequency Journal of Coastal Research alone published 14.4 per of co-occurrence) with each other? cent of the papers published in the top 25 journals  hat are the links between the authors' home 2. W and 7.26 per cent of all papers published in all 1,790 institutions (described by country where the journals. institution is located) if examined in terms of the frequency of co-authorship of publications? The analysis conducted on the first question reveals seven clouds of terms (Figure 5). The first word cloud (purple) describes terms used together in generalist geographical or social- ecological papers covering coastal evolution challenges, impacts on human communities and ability to adapt strategies. The words of sociology or human geography (households, women, livelihoods, coastal communities) are in this cloud. The coasts Figure 4 - Breakdown of articles published in Web of Science related of Nigeria and Ghana are typically associated with to coastal environment topics and related to West African region (25 first such terms. journals). Results of the BCER, no filter, n = 179. An interesting conclusion of this analysis is that scientific communication on coastal environment related to West Africa is less widely distributed among journals, as more than half of the published literature is concentrated in the top 25 journals. In comparison, at a global level, the top 25 journals account for only one third of the published material. Nevertheless, within this set of 25 highly prevalent journals, there is an equitable distribution in the West Africa region, with a less predominant Journal of Coastal Research, closely followed by Journal of Coastal Conservation. In order to select the final list of documents related to the core relevant domain in West Africa, text mining analysis was then applied. All titles, keywords and Figure 5 - Text mining analysis of terms content in 95 papers selected as abstracts of the 179 documents were carefully read to core topics of interest related to West Africa (conditional analysis based eliminate irrelevant elements. This selection resulted in on co- occurrences). 88 Figure 6 - Text mining analysis of authorship of publications and co-authorship, by referring to countries of authors’ home institution. Links are apparent if there are at least two co-published papers. The second word cloud (green) includes terms which The seventh word cloud (black, in the centre of capture the drivers of climate change and rising sea- Figure 5) includes the terms estuaries, dams, floods, levels. It refers to human responses to processes breaches and Senegal River. It refers to the case of (adaptation, scenarios), without looking at the Saint-Louis of Senegal. communities of actors’ details. The following analysis (Figure 6) focuses on the Figure 5 - Text mining analysis of terms content in authors and co-authors of publications by referring 95 papers selected as core topics of interest related the authors to the countries of their home institutions. to West Africa (conditional analysis based on co- This allows us to infer where the papers originate from occurrences). and who collaborated with whom. The third word cloud (orange) focuses on physical Figure 6 - Text mining analysis of authorship of processes such as erosion, as well as engineering publications and co-authorship, by referring to solutions including groynes, seawalls and breakwaters. countries of authors’ home institution. Links are Senegal as a country is frequently mentioned. apparent if there are at least two co-published papers. The fourth word cloud (colour) not only focuses The analysis shows that there are two rather on water quality, groundwater, pollution and disconnected poles of publications: the first is formed contamination, but also contains the word ‘sediment’ by the research institutions of the United Kingdom, (which links to the orange cloud). Ghana and Nigeria, generally involving other English- speaking countries. The second group of institutions The fifth word cloud (blue) includes geographical come from French-speaking countries involving terms from the Gulf of Guinea countries, without Senegal, Côte d’Ivoire, Benin and Belgium. Co- words reflecting a particular topic. publication involving institutions from both groups of countries is rare. The sixth word cloud (grey, top of Figure 5) refers to the words harbour, infrastructures, urban area and the country Mauritania. 89 Credit: Hen Mpoano For more than a decade, the West African coastal countries have suffered from the adverse effects of coastal erosion exacerbated by climate change, jeopardizing the high socio-economic, environmental, and cultural potential of their coastal zones. If nothing is done, the vulnerability of the socio-economic infrastructure, natural resources and coastal populations will only grow, leading to an ever-increasing loss of wealth in the region. The West Africa Coastal Areas Management Program (WACA) is a convening platform that assists West African countries in sustainably managing their coastal areas and enhancing their socio-economic resilience to the effects of climate change, facilitating access to technical expertise and financial resources. waca@worldbank.org wacaprogram.org