Topography, Slope and Geomorphology’s Influences on Shoreline Dynamics along Dakar’s Southern Coast, Senegal

Abstract

Among the impacts of climate change in West Africa, coastal erosion is the most threatening disaster apart from floods and the increase in temperatures. The southern coast of the Dakar region, as part of the most threatened coastal zones in West Africa, records the most current coastal damages in Dakar due to its coastline dynamics and low-lying area. This paper investigates the influences of the topography and slope of the beach on shoreline dynamics using remote sensing, cartographic tools and statistical methods such as linear regression. It also states the important role of geomorphologic structures in shoreline dynamics. It was conducted in three littoral cells (Mbao, Bargny and Toubab Dialaw) along the southern coast of Dakar. It helps to understand better the role that topography, slope and geomorphology play in coastal dynamics. The Modified Normalized Difference Water Index (MNDWI) was employed to delineate the coastlines before computing the dynamic rate of the coastline using Digital Shoreline Analysis System (DSAS) software. After that, the topography and slope were determined using a digital elevation model (DEM). Then, the correlation between the coastline dynamic, topography and slope was analyzed using the coefficient of correlation and linear regression model. In the Mbao and Bargny littoral cells where the geomorphology is mostly dominated by soils little or not evolved in situ, there is a significant relationship between the coast line dynamic, topography and slope with a coefficient of correlation of about 0.63 and 0.87, respectively. The relationship is not significant in Toubab Dialaw, where the topography and slope are high, and the geomorphology is mainly characterized by a category of sandstone, with a coefficient of 0.15. We conclude that topography, slope and geomorphology play an important role in the shoreline dynamics in the study area.

Analysis of Manyas Lake Surface Area and Shoreline Change Over Various Periods with DSAS Tool

“…The boundary between land and water mass is formed by coastlines. Coastlines undergo changes in long and short periods under the influence of tectonic and eustatic movements, wave and sea currents, materials transported by fluvial processes and anthropogenic activities (Erol, 1989;Tian et al, 2020;Pouye et al, 2023). Temporal and spatial detection of the changes that occur and modelling with quantitative data play a very important role in the planning and management of coastal change and in determining the extent of change and risk of ecological conditions (Davidson-Arnott, 2010;Grottolli et al, 2023).…”

“…The advancement and retreat of the shoreline with different origins leads to coastal erosion and coastal accretion (Bird, 2008;Turoğlu, 2009;Pouye, et al, 2023). This situation can affect many natural and human elements on the coast and cause the emergence of different risks (Wu et al, 2022).…”