A study on the slope-gully erosion relationship on small basins in the loess areas at the middle reaches of the Yellow River

The erosion characteristics of the upper slope runoff and the slope gully erosion relationship are discussed based on the data of runoff and sediment yield from gauging stations in the loess areas at the middle reaches of the Yellow River. Sources of sediments in typical small catchment are determined based on the concept of net increment of sediment yield by using analytical method of sediment formation at different positions in a catchment. The result shows that sediments in a small catchment at the middle reaches of the Yellow River mainly come from slopes. This paper indicated that the sediment sources from slopes are roughly 55, and 85 percent of the total sediment yield of the small catchments in Yangdaogou, and Nanxiaohegou, respectively, due to impacts of varying degrees from upper slope runoff. Under a critical condition, erosion characteristics of slope would change. In yangdaogou and wangmaogou , the critical value are about 319 kg/m 3 and 362 kg/m 3 under multi years (or multi times) rainfall condition, respectively.