Morphodynamics and Evolution of Estuarine Sandspits along the Bight of Benin Coast, West Africa

Stephan Korblah Lawson,Hitoshi Tanaka,Keiko Udo,Nguyen Trong Hiep,Nguyen Xuan Tinh

doi:10.3390/w13212977

Abstract

It is well known that estuarine systems are significantly affected by hydrodynamic conditions such as river discharge, storm surges, waves and tidal conditions. In addition to this, human interferences through developmental projects have the capability of disrupting the natural morphological processes occurring at estuaries. In West Africa, the goal to improve standards of living through large-scale dam construction, offshore ports and coastal erosion countermeasures has triggered alarming changes in the morphodynamics of estuarine systems. The estuaries at the Volta River mouth (Ghana) and “Bouche du Roi” inlet (Benin), located along the Bight of Benin coast, West Africa, were selected as two case study sites to examine their long-term morphodynamics and sandspit evolution. In this study, we primarily analyzed estuarine morphology using remotely sensed images acquired from 1984 to 2020. We further estimated the longshore sediment transport for this region using results from the image analysis and the depth of active sediment motion. Our results reveal that the longshore sediment transport rates for this region are in the magnitude of 105–106 m3/year. Comparative analysis with other estuaries and sandy coasts suggests that the longshore sediment transport along this coast has one of the largest rates estimated in the world.

Highlights

The results from this study suggest that the longshore transportof rates (LSTR) are in the order of 105 –106 m3 /year for the Bight of Benin coast (Figure 17)
Available remotely sensed images were used to quantify sandspit growth and longshore sediment transport rates by applying a simple analytical model based on the conservation of sand volume
Estimates of longshore sediment transport along this coast were in the order of 105 –106 m3 /year

Summary

Introduction

Estuarine systems are among the most essential ecological environments in the world and support socio-economic growth and the biodiversity of the natural environment [1,2,3]. The morphological evolution of estuarine systems and the forces driving this evolution have been of interest to coastal researchers, especially at river mouths and tidal inlets [4,5,6,7,8,9,10]. The morphodynamics of estuarine systems, i.e., wave climate variability, sediment supply, tidal exchange and river discharge, controls evolutionary processes and requires a thorough understanding through extensive research [11]. Assessment of the impact of human interferences on estuarine morphology is of great importance to distinguish between naturally and artificially induced evolutions

Results

Discussion

Conclusion