One new sediment yield model for single storm events and its application at annual time scale
一种新的流域水沙关系模型及其 在年际时间尺度的应用

The loess gullied-hilly area of the Loess Plateau in North China is one of the most severely eroded regions in the world with a mean annual soil loss rate exceeding 10000t/ km^2. Based on the observed data here from two stations, the relationship between runoff and sediment yield is examined for single storm events. In the study area, sediment concentration keeps stable when flow discharges are in excess of some critical values, and mean sediment concentration for single flood events mainly depends on the heavy-discharge stage in flood duration. Thus, the mean sediment concentration also keeps stable for heavy flood events. Therefore, one new runoff-sediment relationship model is established for specific watershed. M= Ch, where M is area-specific sediment yield, h is runoff depth. Furthermore, this model has excellent applicability due to the importance of extreme events for soil loss in the study area. The results of the model applied to the annual timescale showed that the model can predict the annual sediment yield very well for the watershed without base flow; and for the watershed where base flow exists, the model can also obtain a good estimation in wet year using the total runoff volume occurred in flood season.