A GIS-Based Modeling Of Soil Erosion And Sediment Yield For The Typical Watersheds And Scale Study In Hilly Loess Areas, North China

Soil erosion and sediment yield models are effective tools for managing water and soil resources,quantificationally evaluating the benefit of water and soil conservation measures and the disaster of soil erosion.The distributed divides the valley into a lot of cells(small drainage area or grids or land plots) so that each unit possesses approximately the same conditions(Soil,vegetation coverage,slope,land use patterns,rainfall).In this way,it can avoid the excessive homogenization of model parameters and the differences with the actual result of the natural conditions.There are a lot of soil ersion and sediment yield models around the world at present.These models offered a good reference for my project.However,these models were built based on gentle slope.The Loess Plateau in north Chian has distinct characteristics in the terrain,topography,land use patterns,and rainfall characteristics.These established models therefore cannot be applied in this region.Generally,this paper analyzed the impact of landform,physiognomy,rainfall of loess hill donga area to the soil erosion and sediment yield of drainage basin;the spacial and temporal effect of soil erosion and sediment yield of drainage basin;the current of soil erosion and sediment yield of drainage basin,and use GIS,VB.NET+SQL SERVER2000+ ARC Engine9.2 to develop the distributed soil ersion and sediment yield model of shejiagou.Which have three modules that are compile and browse of space data, compile and browse of attribute data and operation of model.The main conclusions of this paper were summarized as follows:(1) The characteristic of sediment yield of loess hilly area is examined.Through analyzing the effects of rainfall,slope gradient and slope length on slope erosion,the influence of rainfall on slope erosion and sediment yield is considered to be the most important,slope gradient is the second,and slope length is the smallest.Whether the effect of slope gradient and length are constant or not is also examined,and expatiated the reason of increase or decrease of slope erosion and sediment yield under different rainfall, slope gradient and slope length.(2) The topographical features of hilly loess area,the effects of topographical features on sediment yield and the current of sediment yield are examined.The influence of drainage density on the sediment yield is discussed at different temporal and spatial scales:no simple decreasing relationship is found between drainage density and drainage;the spatial scale effects of drainage density is associated with grid sizes;the area-special sediment yield does not present a simple positive correlation with drainage density.The impact of the gully on sediment yield is related with its level and position,and varies with the spatio-temporal scale.(3) Under different time scales,including the single rainfall events,months and years, erosion and sediment yield of several spatial scales ranging from the hillslope to watershed were analyzed.And the relationship between temporal scales,spatial scales and erosion and sediment yield were analyzed.The study indicates that the area-specia sediment yield presents a substantial change at small time scales,implying that the time scale gives much more influence on the sediment yield than the spatial scales.However, the spatial scale effect emerges under large time scales,because the turbulent phenomenon under small time scales was smoothed by the effect of accumulation.(4) Based on the DEM and rainfall data,map of land use,map of physiognomy,and of the rainfall data in the studied basin,together with the characteristic of runoff and sediment yield in this area,a distributed model is established for predicting soil erosion and sediment yield according to the status of shejiagou.This model setting is universal in gullied-hilly area of loess plateau,so this model can be take in similar watershed which in gullied-hilly area of loess plateau through revising CN,and this study can afford a reference for soil and water conservation in gullied-hilly area of loess plateau.