Pattern and mechanisms of sediment distribution in Lake Victoria

81 An investigation was conducted on the applicability to Lake Victoria of three generalizations on lake sediment distribution namely, that (1) sediment resuspension results almost entirely from the action of wind-induced surface waves; (2) sediments are distributed in a focused pattern; and (3) surficial sediment characteristics (particle size, bulk density, water content and organic matter content) vary systematically with increasing water depth and fetch. From application of two complementary techniques, it was found that the distribution of sediments does not closely follow any of the above generalizations. A belt of proximal-distal progression in sediment character exists in northern Lake Victoria that cannot be explained by wave theory. Surficial sediment characteristics also do not change systematically with depth or fetch. The findings indicated that focusing results only for the case where the wind vector is of variable direction. The anomalies together were taken to suggest a strong influence of currents in sediment distribution. It was accordingly argued that for large lakes with relatively shallow basins, prediction of sediment resuspension and transport from surface wave action without considering the possible influence of currents may not provide a full picture of sediment distribution processes in operation. In processes suggested to explain the anomalies in Lake Victoria, it is proposed that morphometric, hydrological and meteorological factors come together to mix and disperse sediments via the epilimnion, and produce alongshore and cross-isobath currents that transport sediment northwards and northeastwards from the western shore.