Study On The Regular Of Rainfall Runoff And Sediment Yield In The Small Watershed In Dabie Mountain Area Of Anhui Province

Dabie Mountain area in Anhui is one of the areas with more serious soil erosion in China.The study of rainfall,runoff and sediment yield regular of small watershed in Dabie Mountain area of Anhui can provide scientific basis for monitoring and evaluating soil erosion in Dabie Mountain area of Anhui.Based on the rainfall data,hydrological data,vegetation cover data,socioeconomic factors data and land use data of Jiangzi River small watershed from 2012 to 2019,this study explored the characteristics of rainfall,runoff,sediment yield and the relationship among them at two scales of slope runoff plot and small watershed.Random forest,association rules and stepwise regression analysis were used to explore the influencing factors of soil erosion.The results showed that:（1）The runoff depth and the amount of soil loss in the slope runoff plots vary greatly from year to year.The sweet potato measures had the largest runoff and soil loss,and the tea was the smallest,the growth rate of erosion in the runoff plot was sweet potato>mulberry>tea>chestnut>soybean>camellia oleifera.The trend of runoff and sediment yield in slope runoff plots were relatively consistent with the change of rainfall.Heavy rainfall,high rainfall intensity,and long duration rainfall was the main rainfall patterns that caused soil erosion on slopes.Rainfall was the main rainfall factor that affects runoff generation,rainfall×rainfall intensity（PI）,rainfall×maximum 60min rainfall intensity(PI₆₀),rainfall（P）,and maximum 30min rainfall intensity(I₃₀)all had an impact on the amount of soil loss in slope runoff plots,while the impact of maximum 60min rainfall intensity(I₆₀)on runoff and sediment yield was relatively low.（2）The annual variation of rainfall in Jiangzi River small watershed was large,the distribution of runoff depth was uneven between years and within years,and the minor rain was the main rainfall grade type,the distribution of runoff depth was uneven between years and within years,and the runoff depth was significantly related to rainfall.Rainfall duration,rainfall intensity,PI and PI₆₀ were the main rainfall factors of runoff production.The annual and intra annual distribution of sediment yield was uneven,and it was significantly different from rainfall.The rainfall,rainfall intensity,I₃₀,PI₃₀,PI and PI₆₀ were the main rainfall factors for sediment production,which can explain the change of 98%of sediment transport.（3）The rainfall in slope runoff plots with different crop measures had a good correlation with the slope soil erosion modulus.The importance of soil erosion factors was ranked as follows:rainfall>vegetation coverage>crop type>engineering measures>slope>slope position>slope direction>soil layer thickness.Slopes of 19°and 13°,vegetation coverage between 25%-55%and 60%-95%.Moderate,light rain and heavy rain caused less soil erosion.The water conservation effect of tea,camellia,soybean causes chestnut were better.The soil erosion degree of slope to ladder runoff plot was less than that of slope farmland runoff plot.（4）The hydrological,climatic and vegetation characteristics of Jiangzi River small watershed can explain 47.18%,45.66%and 6%of soil erosion respectively,the social and economic characteristics and land use characteristics had little influence on soil erosion.The main influencing factors of soil erosion were rainfall,construction land area ratio,runoff and temperature,which could explain 76.6%of the change of erosion.