Evaluation Methed Of Urban Stormwater Low Impact Development Based On I-Tree Hydro

In recent years,Urban surface runoff of China increased significantly,and the surface runoff with a large amoumt of organic matter,nutritive matter and suspended solids flowed into water bodies raised flood,water pollution and caused other problems.Research shows that the impervious cover will facilitate the formation of surface runoff in the rainfall process,and the surface runoff with kinds of contaminations flowed into water bodies,the change of land cover has become one of the important reasons for environmental degradation.Accordingly,Low Impact Development gradually attracted more attention because of its management concept of urban stormwater.With the accelerating industrialization and urbanization,the impact of impervious cover on watershed hydrology environment in Jing-Jin-Ji has been a focus research.This paper analyzes the urban and rural construction land area and impervious cover area ratio of Beijing,Tianjin and 3 prefecture-level cities in Hebei during the years of 2000 to 2013.Impervious Cover Model was used to evaluate the urban hydrology environment so that we can provide suggestions for urban planning.In order to evaluate the rainfall runoff control effects of LID Practices in developed area,i-Tree hydro model was applied to simulate the impact of LID practices on rainfall runoff and pollutant load in Shihe residential area of Jiaxing,Zhejiang province.Onsite monitoring data and local data of soil type,topography,precipitation,evaporation and land cover were used as input to analyze three scenario of historical(2006),current without LID and planning with LID.The result shows that total runoff of planning scenario can be reduced by 31.52% compared with current without LID,and is increased by 9.96% compared with the historical scenario.Statistical analysis shows that the annual runoff is directly related to land cover;the impervious and annual runoff are negatively related to vegetation cover rate;while the base flow and pervious runoff are positively related to vegetation cover rate.It shows that the annual total load of three pollutants can be reduced by 513.66 kg,the reduction rate of TSS,COD and TP load is 49.85%,50.30% and 36.36% respectively under the planning scenario compared with current without LID.Therefore,LIDs have obvious reduction effect of runoff and pollutants.