Grid Scale Effects on Watershed Soil Erosion Models

The model CASC2D-SED was applied to the Goodwin Creek experimental watershed in Mississippi to define erosion model response to raster-based grid cell sizes. The model was parameterized at a 30 m grid, then calibrated and validated to three representative thunderstorms. The simulated hydrographs replicated the measurements of peak discharge, runoff volume, and time to peak. The model also calculated sediment yields within ±50% of the field measurements. Resampling the watershed digital elevation model at scales from 30 m to 330 m reduced the land surface slopes and changed the channel topology. In general, very good modeling results are obtained at grid sizes of 30 m and 90 m , which is comparable to the plot sizes of the universal soil loss equation. At grid sizes coarser than 150 m , the sediment source areas became less appropriately depicted and the calculated sediment delivery ratios became unrealistically high. Grid sizes smaller than 150 m are recommended for proper watershed simulation of upland e...

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