Study On Main Control Indexes And Countermeasures Of Soil And Water Loss In Small Watersheds Of Haidian District

This paper takes three typical small watersheds in Haidian District of Beijing as the research object,and establishes the land cover database of Haidian District through the accurate visual interpretation of the underlying surface of Haidian District,aiming at the mountain soil erosion control zone,groundwater source conservation film and urban runoff control.The soil erosion equation,SWMM model and optimization equation model were used to study the three major control indexes of soil erosion,runoff water quality and comprehensive runoff coefficient.On this basis,the relevant measures of soil erosion control at the basin scale were proposed.The main findings are as follows:(1)The Bei'an River Basin belongs to the mountainous watershed.The 0°-15° plain and the mountain-plain interlaced zone are slightly eroded by the soil erosion intensity within the allowable soil erosion intensity;the forest areas above 150 are all mild erosion intensity.In the forest areas with slopes of 15°-25°,the soil erosion intensity is dominated by "light I",the erosion area accounts for 17.25%of the total area of the basin,and the forest area with slopes greater than 250-350,the soil erosion intensity is mainly "The light ?" level is dominant,the erosion area accounts for 13.62%of the total area of the basin;the forest area with slope>35°,the soil erosion intensity is also dominated by the "mild ?" level,and the "light ?" level erosion occurs in a small number of areas.The erosion area accounts for 2.46%of the total area of the basin.The basic conditions of the soil erosion control zone are similar,and the soil erosion intensity is controlled as the soil erosion control index.(2)The water source conservation area is located in the plain area of Haidian District.Because its scope involves groundwater source protection areas,the main goal of controlling non-point source pollution is to prevent the water quality of the water source from being polluted.The pollutants carried in rainfall runoff are an important threat to the water environment quality in the region.The water quality is simulated by SWMM.The initial runoff carries a large amount of SS pollutants,and its peak concentration decreases with the increase of the return period.LID measures The TSS load in surface runoff can be significantly reduced.The rainwater garden,permeable pavement and green roof have the most significant effect on TSS load reduction in the case of low return rainfall.The combination of the three LID measures is more effective in reducing the surface runoff TSS load in the basin.(3)The urban runoff control zone has a high urbanization level,and the integrated runoff coefficient of this area is 0.59,which is the highest in the whole region.The main measures for controlling the runoff coefficient in the built-up area include green space reconstruction,permeable pavement renovation and green roof renovation.Various measures can be flexibly deployed on most of the underlying surface of the city.This is to reduce the risk of urban flooding and realize the effective use of urban rainwater resources.The most direct and convenient means.