Investigation of Beach Morphodynamics at Elegushi Beach, Lagos State

Beach morphodynamics describes the continuous adjustment of beach form in response to hydrodynamic forcing by waves, tides, and currents, and understanding these processes is essential for coastal engineering and management. This study investigates the morphodynamic behaviour of Elegushi Beach, Lagos State, South West Nigeria, a high-use recreational and residential coast subject to persistent erosion concerns and recent storm events. Monthly beach profiling surveys are conducted along eight cross-shore transects for twelve months during 2023 to 2024, using a real-time kinematic global navigation satellite system to measure beach face elevation, foreshore slope, berm position, and dune height. Concurrent wave measurements from a nearshore wave rider buoy provide incident wave height, period, and direction data. Sediment samples from the foreshore and backshore are analysed for grain size distribution using laser diffraction to classify beach type and compute dimensionless fall velocity. The beach state classification scheme of Wright and Short is applied to characterise morphodynamic states across seasonal cycles. Results are expected to demonstrate a transition from dissipative to intermediate beach states during the wet season as incident wave energy increases and sediment transport volumes peak. Volumetric change analysis reveals episodic erosion at the northern end of the study beach linked to longshore drift reversals. Recommendations address the urgent need for sustainable beach nourishment and the installation of groynes to interrupt sediment bypassing. Keywords: beach morphodynamics, Elegushi Beach, Lagos, coastal erosion, wave forcing