Characteristic of Runoff and Sediment Yield and Its Influencing Factors Analysis on Slope Scale of Small Watershed in Northwest Hunan

Based on 2004-2008 observed data on runoff plots of Nverzhai small watershed in Wuling mountain of northwest Hunan,this paper discussed runoff and sediment yield characteristic and its influencing factors on slope scale.This will provide reference for evaluating vegetation restoration in watershed.The result showed that shrub and Pingii community had preferable benefit to prevent soil and water loss.Tung tree were comparatively worse.Natural vegetation restoration also had better benefit.Average runoff and sediment yield of slope farmland were the maximum,this illuminated that vegetation and natural restoration had better effect of soil and water conservation.Relativity between rainfall(P) and runoff and sediment yield on slope were the most from rainfall factors.The next was rainfall erosivity(R).Relativity between I10 and runoff and sediment yield on slope were the least,its correlation coefficient were basically less than 0.5.Mutiple stepwise regression analysis showed that rainfall factors had evident effect on runoff and sediment yield.The trend of sediment changed following with runoff on slope farmland were the most,its decision coefficient(R2) was 0.769 3.The trend of shrub were the least,its R2 only 0.425.Based on grey relational analysis to kinds of factors about vegetation,landform and soil affecting runoff and sediment yield on slope scale,these factors had evident effect on runoff and sediment yield and its grey relational degree were all exceeded 0.5.Total cover of vegetation had most effect on runoff and sediment yield on slope,this showed vegetation had preferable benefit for soil and water conservation.Vegetation restoration were the main measure for improving ecology environment in this region in future.