Numerical assessment of potential sea level rise impacts on coastal retreat along the Nigerian Mahin mud coast

The Mahin mud coast of Nigeria, West Africa, has experienced fluctuations in coastline changes over decades, with retreat being the dominant process along the coast. Aside from the geotechnical characteristics of the terrain, placing it vulnerable to sediment loss from the impact of ocean waves, steady sea level rise is also responsible for its recession and accretion at different locations. Because of the severe retreat and repetitive flooding cases reported in the area, this study investigated the hydrodynamics nearshore and under some potential sea levels. The coast was divided into three sectors. A numerical model was set up using MIKE 21/3 coupled (hydrodynamic and spectral wave) model to present the area’s first sea level assessment and prediction simulations. Results revealed that the central sector has the highest water levels and ranges during the simulated period and the highest water levels after sea level rise projections. In addition, the rate of increase in sea level is highest in the western and eastern sectors, respectively, where they closely border the central sector. Nevertheless, the coast’s elevation and slope analysis indicated that the eastern sector is the most vulnerable to sea level rise. The study presents details of factors that influence the region’s morphology and amplify the risks of its hydrodynamic processes, particularly during the spring tide. Hence, this study captures the events along the coast in order to point out the areas of future risk.