Research On Decomposition Method Of Volume Capture Ratio Of Annual Rainfall Of Buildings And Communities

Since reform and opening-up,our country has experienced a period of rapid development in the past 40 years,and now our country has become an urbanization country which has a huge transformation of urban development.Under the extreme pressure of high-speed urbanization and wild climate,the contradiction between urban development and urban water ecological environment is increasingly prominent.Under this background,the idea of “Sponge City” becomes a hot spot and arises extensive attention.Actually,the idea of “Sponge City”,a new generation management idea of urban rain-water flood basing on low impact development,its connotation is to deal with the problems of urban rain-water flood at the angle of the overall development of our cities,and it stresses the fulfillment of the comprehensive goal guiding with the ideology of eco-civilization.The construction of “Sponge City” 's core quota is the volume capture ratio of annual rainfall.However,in the process of construction of “Sponge City”,different regions have different understandings of the volume capture ratio of annual rainfall.Therefore,how to decompose the volume capture ratio of annual rainfall quota scientifically and reasonably is a problem to be solved urgently in the next period of construction of“Sponge City”.In this paper,it chooses a residential district in Suichang County as the main study object to analyze the decomposition method of the volume capture ratio of annual rainfall of buildings and communities.And the method consists of the following steps:1.Analyzing and evaluating the low-impact development measures(LID)combining with the characteristics of the residential area.In this way,we can select the appropriate low-impact development measures including infiltration pavement,rain garden,and sunken green belt,green roof,etc.which is suitable for the residential area by considering the effects of runoff control,applicability,economy and so forth.2.Taking a comprehensive consideration of the current situation of the community such as fundamental underlying surface,pipe network layout,planning materials,etc.,combining with the low-impact development measures has been taken,and making use of “the artificial weighted average trial decomposition method”(also known as the weighted average method)to decompose the quota of the control aim of total annual runoff volume of the residential area,and in this way we can obtain the volume capture ratio of annual rainfall.3.Constructing the SWMM model combining with the actual situation of the residential area.(the model of managing the storm and flood,version:5.1)In this model,the rainfall data is obtained basing on the Chicago rain pattern and the highly sensitive hydrological parameters is corrected by the Morse method to obtain more valuable numerical simulation.Comparing “the SWMM model method” with “the weighted average method”,the following conclusions can be drawn:(1)When P(the return period)=0.5,the volume capture ratio of annual rainfall obtained by “the SWMM model method” and “the weighted average method” are respectively 69.5% and 71.4%,and the results keep conformity.Moreover,when establishing the low return period of a certain region(P?0.5),these two methods can all be used to calculate the volume capture ratio of annual rainfall.However,in the case of medium and high return period(P?1),the volume capture ratio of annual rainfall simulated by the SWMM model is more realistic.(2)There are many parameters which will be involved in the calculation process of “the SWMM model method”.Considering the problem of sensitivity of parameters,adjusting the characteristic width value of sub catchment area can further reduce the error with the result of “the weighted average method”.(3)“The SWMM model method” can fully play its role in the water storage effect of storage layer with various LID measures.Therefore,the volume capture ratio of annual rainfall calculated by combining these two methods is more precise and accurate,this combination way is more suitable for quota decomposition and the guidance of following construction in building the blocks of “Sponge City”.