Experimental study of erosion by waves on the lakeshore of lateritic soils

Abstract Many countries use hydropower as their main source of power generation. One of the factors responsible for erosion in hydroelectric reservoir margins is the action of wind-induced waves, which increases sedimentation and reduces their storage capacity. Despite potential economic and environmental damages, research into wave erosion processes on reservoir margins are found mainly in cohesive soils from cold regions. Research on erosion by waves of cohesive soils from savannah regions, which are commonly found in tropical reservoirs, is incipient; studies evaluating breaking and non-breaking wave conditions on this type of erosion are especially important. This work presents the results from 18 water wave channel experiments which were conducted to investigate the erosional processes by waves on lateritic soils, under breaking wave and non-breaking wave conditions, as well as determining the spatial distribution of the resulting sediments. Lateritic soil samples were placed on the wave channel and different conditions were tested. Wave frequencies varied from 0.272 to 0.999 Hz on four different beach slope angles of 22.50, 30.00, 45.00, and 60.00 degrees. In 80% of the tests, the erosion rate varied positively in a nonlinear form with the increase of the accumulated wave power. However, when the waves broke, erosion rate sometimes varied negatively and the sediment production tended to be reduced. High precision 3D surveys showed a good agreement between the maximum depth of the eroded surfaces and the power increase of the waves. The average roughness of the samples increased in 90% of the tests. The spatial distribution of sediments and their grain size distributions were also investigated. The waves’ driving forces were incapable of transporting the sediments away from their source of origin and, therefore, were not able to change the natural distributions of the grains with the simulated conditions.