Suspended sediment transport by rivers in the different climatic zones of Cameroon (Central Africa)

摘要

Some watersheds representing the major climatic zones of Cameroon, in Central Africa, have been simultaneously investigated during the period 2002-2004. The patterns of monthly suspended sediment transport show a common form. In areas with a tropical climate, there is a hysteretic loop, with the maximum concentration preceding the flow peak. In these areas, the values of suspended sediment concentrations (up to 3000 mg L~(-1)) and specific sediment yields (>200 t km~(-2) year~(-1)) are high. In contrast, in areas with an equatorial climate, the monthly concentrations increase regularly with the monthly flow and sediment concentrations are about 15 mg L~1 and specific sediment yields less than 10 t km year~(-1). A comparison of recent results and historical data shows that in areas of dry tropical climate (Mayo Tsanaga) where flow rates have decreased by 50% since the late 1960s, average sediment concentrations increased from an overall average of 1050 to 2500 mg L~(-1), with a maximum exceeding 3000 mg L~(-1) in 2003. Conversely, in the equatorial zone (Ntem), the available data indicate no major change in sediment concentrations despite a decrease in flow rate of 19%.