A GIS-Based Model for Estimating Runoff Sedimentation in Semi-Arid Wadies

Abstract

A spatially variable model using the USLE (the Universal soil loss equation) in a GIS (Geographic Information System) environment was developed for the estimation of sediment loads in arid and semi-arid regions. The model theory is based on a modification of the Universal soil loss equation (USLE) for predicting soil loss magnitude. The spatial capabilities of GIS (Geographic Information System) are used to represent the RUSLE predictors into spatially variable grids where the USLE is applied on a cell-by-cell basis. Accordingly, a nominated name for the model is SVUSLE (Spatially Variable Universal Soil Loss Estimator). Each grid pixel in the model is treated as an in-depended hydrologic unit (mini-sub-catchment) where the soil loss is estimated as a function of the USLE predictors. The consideration of spatially variable predictors enables the accurate estimation of soil loss since the USLE predictors (slope-length, soil type, and rainfall) are highly variable in space. The model is tested on a case study from Wadi Watier in South Sinai. The results showed reasonable agreement between the sediment loads estimated by the model and those measured in the field. The assessment of the model indicates that the model has high potential for the engineering applications since it is accurate, practical, and fast.