Effect of vegetation and other measures for soil and water conservation on runoff-sediment relationship in watershed scale

According to the characteristics of hyper-concentrated sediment flow, the relationship between runoff and sediment yield can be expressed by linear regression relation and the sediment transport capacity, stable sediment concentration during the flow discharge excess the critical value as well as the average sediment concentration for each flood in watershed can be expressed by different regression coefficients. By using this model the effect of vegetation and other measures for soil and water conservation on relationship between runoff and sediment is investigated by means of comparing the differences of sediment yield and runoff in two typical small watersheds with similar geological characteristics, in which one watershed without soil and water conservation measures and the other having the vegetation area greater by 75% and other soil and water conservation measures. It is found that the runoff-sediment relationship in these two watersheds is the same but the sediment yield is reduced due to the reduction of runoff. The vegetation and slop prevention measure can not effectively reduce the hilly erosion. It may conclude that in case only vegetation and slope prevention measures are adopted for water and soil conservation the sediment reduction rate by means of these measures can be estimated by using reduction rate of runoff. The effectiveness of this method is verified by application examples.