Assessing of Impacts of Climate Change on Sea-level Rise and Shoreline Evolution Case of the East Coast of Cotonou in Benin, West Africa

Abstract

Climate-change-induced sea level rise (SLR) poses a critical threat to coastal zones worldwide, with heightened impacts in low-lying, rapidly urbanizing regions. The East Coast of Cotonou, in Benin, is a hotspot of vulnerability, where the rapid retreat of the shoreline intersects with dense settlements, critical infrastructure, and socioeconomic pressures. This study investigates the multidecadal dynamics and their socioecological implications by integrating global datasets, standardized analytical tools, and field-based evidence using a triangular methods approach. A systematic review of the literature using PRISMA guidelines synthesized global and regional knowledge on SLR, shoreline change, and coastal vulnerability, highlighting significant gaps in localized assessments for West Africa. Satellite altimetry and tide gauge data were analyzed to assess global and relative sea level trends, while Landsat-derived shoreline positions were processed using the Digital Shoreline Analysis System (DSAS) to calculate linear regression and endpoint rates, uncertainties and identify erosion hotspots. These remote sensing and statistical results were validated through detailed field surveys along the eastern shoreline, including beach profiling, GPS mapping, and community interviews. The results indicate a persistent SLR trend averaging 3.4 mm / year in the Gulf of Guinea, consistent with global acceleration patterns. Shoreline analysis revealed average erosion rates of –3 to -5 m / year from 1985 to 2020, with localized hotspots exceeding -7 m / year, particularly near Akpakpa and east of the Cotonou port. Field observations confirmed significant beach narrowing, infrastructure loss, and adaptive responses. Socioeconomic participation highlighted disparities in coping strategies, declining fish and agricultural productivity, and governance gaps in coordinated coastal adaptation. The study concludes that the eastern coastline is undergoing rapid erosion driven by the interplay of global SLR, regional hydrodynamics, and local anthropogenic pressures, producing profound socioecological consequences. The recommendations emphasize the urgent need for integrated, context-specific adaptation strategies: (i) strengthening the coastal protection infrastructure in hotspot zones, (ii) regulating sand mining and other anthropogenic activities, (iii) promoting community-based adaptation and relocation planning, and (iv) improving governance frameworks to support equitable, sustainable coastal management. By linking global climate processes with local realities, this research provides actionable evidence to guide resilience building and policy development in coastal contexts in West Africa.