Dynamic Erosion and Sediment Yield Model Analysis in a Typical Watershed of Hilly and Gully Region, Chinese Loess Plateau

The Purpose of this study are to (i) develop and update a yearly distributed model of watershed erosion and sediment yield and (ii) assess spatiotemporal changes in erosion and sediment yield in the Majiagou River watershed before and after projects to return farmland. In addition to degrading soil fertility and natural resources, soil erosion also contributes to the sedimentation of river channels. A distributed-dynamic model of sediment yield based on the Chinese Soil Loss equation (CSLE) was developed and modified to evaluate the effects of hydrological factors and human activities on erosion and sediment yield between 1995 and 2013. This was done in order to discover the spatiotemporal evolution of erosion and sediment yield before and after returning farmland in a typical watershed of a hilly and gully region (Chinese Loess Plateau). Results could offer a solid scientific foundation for the management of watersheds, land use planning, and multi-scale dynamic modelling of erosion and sediment yield. The modified model has characteristics of simple algorithm, high accuracy, wide practicability and easy expansion, and can be applied to predict erosion and sediment yield in the study area, 2) soil erosion gradations are closely related to the spatial distribution of rainfall erosivity and land use patterns, the current soil and water conservation measures are not efficient for high rainfall intensities, 3) the average sediment yield rate before and after model modification in recent 5 years (in addition to 2013) is 4574.62 Mg/km2 and 1696.1 Mg/km2, respectively, decreasing by about 35.4% and 78.2% when compared to the early governance (1995-1998). However, the once-in-a-century storm in July 2013 is the key factor in the highest possible sediment yield. The hilly and gully region of the Chinese Loess Plateau may benefit from the results as an effective and scientific basis for planning the conservation of soil and water and ecological building.