Sabaki River Sediment Transport and Deposition in the Indian Ocean.

Abstract

The study aimed at investigating transport and deposition of sediments discharged by the Sabaki River into the Indian Ocean. Suspended solids, bottom sediment grain size distribution and mineralogy,and seasonal sediment discharge rates were measured. The Sabaki River discharges 1.18x10 super(6) tons 2.47x10 super(7) tons of sediments per annum. The highest sediment discharge occurs during the N.E monsoon period, attaining a range of 1.11x10 super(5) to 2.27x10 super(5) tons. Sediments in the study area are moderately well to very well sorted. Grain size decreases both across and along shore and ranges from medium to very fine. During the study period, Malindi-Mambrui beach experienced net sediment gain as most heavy sediment grains from the river mouth were deposited along the beach and inter-tidal zone. The plume of total suspended solids facilitates along-shore transport more than across shore transport, and travels beyond the North and South limits of the study area at solids concentration levels of 0.010 to 0.500 g/l and 0.010 to 0.900 g/l respectively. The plume moves both to the north and south of Sabaki river mouth, depending on the monsoon direction. Generally, total suspended solids levels decreased both along and across shore. The lowest mean value of suspended solids was 0.010 g/l, while the highest mean value was 1.85 g/l. Deposition of silty sediments occurred from mid-continental shelf seaward.