Dynamics of fluvial suspended sediment transport and yield in volcanic highland's agricultural basin: case of the Noun River, Western Cameroon

摘要

The dynamics of suspended sediment transport in the Noun River has been quantified using 93 runoff samples. Daily flow and monthly normalized difference vegetation index (NDVI), leaf area index (LAI), rainfall, and dam management data allowed the quantification of the total suspended solid (TSS), on the one hand, and the interpretation of the dynamics of solid transport within the drainage basin, on the other hand. The TSS concentrations range from 3 to 1375 mg L-1 for a volume weighted mean concentration of 90.33 to 110.49 mg L-1 and a specific sediment yield (SSY) of 41 to 57 t km(-2) year(-1). The basin's hydrological characteristics between March to June and December to February have been reversed, revealing a strong impact of a dam. The maximum TSS concentration obtained during the second hydrological year at the beginning of the rainy season (April) is paradoxically three times higher compared to that recorded in July during the first measurement period. This occasional high TSS concentration for the single month of April released sedimentary fluxes superior to those recorded over the period of July to November combined, in comparison to those obtained during the first year. This situation causes sediment depletion not only on the next regular maximum TSS concentrations but also on the quantities of sediments exported later. The monthly TSS concentration/discharge does not present a clockwise hysteresis curve observed on tropical streams such as the Mbam and Sanaga in Ebebda, with annual variations in its evolution.