The area for soil erosion modeling at watershed scale is large

usually dealing with more than one types of climate.Single type of runoff mechanism can not describe runoff generation exactly.A long term soil erosion model at watershed scale is built by taking a grid of DEM as simulating unit and a day as time interval.Dynamic runoff mechanisms are used in the model

which consider runoff as a dynamic process depending on weather and subsurface conditions.The sub-processes of precipitation

infiltration

surface storage

flow velocity

snow melt

and evaporation are incorporated in the regional soil erosion model.RUSLE model is used to calculate soil detachment.Monthly vegetation coverage is used to calculate C factor

so that the C factor is dynamic in the long term simulation and may describe the hydrologic process more exactly.The model is then applied to Linyi watershed for simulation and validation.Results show that the model is applicable in the watershed.Elevation is found to be the main factor to soil erosion.Sediment from the watershed mostly comes from the upstream and midstream and is distributed in the zone of 200～500 m elevation.Therefore

the zone is the main region for the prevention of soil erosion.