Estimating spatial sediment delivery ratio on a large rural catchment
Abstract
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.
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