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soil erosion, sediment yield, sediment delivery ratio, modelling, Masinga catchment, GIS, hillslope


Soil erosion and sediment yield from catchments are key limitations to achieving sustainable land use and maintaining water quality in streams, lakes and other water bodies. Controlling sediment loading requires the knowledge of the soil erosion and sedimentation. However, sediment yield is usually not available as a direct measurement but estimated by using a sediment delivery ratio (SDR). An accurate prediction of SDR is important in controlling sediments for sustainable natural resources development and environmental protection. There is no precise procedure to estimate SDR, although the USDA has published a handbook in which the SDR is related to drainage area. This paper presents a new approach for estimating spatial sediment delivery ratio (SDR) for large rural catchments. The SDR is predicted using a Hillslope Sediment Distributed Delivery (HSDD) model in conjunction with a physically distributed hydrological model in a GIS environment. The new approach was developed and tested on Masinga catchment, a rural large catchment in Kenya. The hydrological model was validated using predicted and observed daily stream flows and a performance criterion based on Nash Sutcliffe coefficient of model efficiency was used. The developed model is not only conceptually easy and well suited to the local data needs but also requires less parameters, which offer less uncertainty in its application while meeting the intended purpose.