| With the gradual acceleration of urbanization in China,the proportion of urban impervious area increases,and the problem of rain flood and waterlogging becomes increasingly prominent.Controlling the total amount of rainwater runoff can well alleviate the urban storm flood problem,and is also the key to the construction of sponge city and green rainwater infrastructure.Sunken green space is a kind of natural green rainwater infrastructure,which has good hysteresis storage efficiency.Because of its unique topography,large geographical slope,low soil infiltration rate,it is difficult to detain rainwater in hilly areas,and there is no natural green space that can detain rainwater effectively,which leads to the contradiction of total control of rainwater runoff more prominent.Therefore,the paper selects a typical hilly urban area as the research object,to quantify the recessed greenbelt under study,study area drainage system model is constructed and researched the recessed green hysteresis purify rainwater storage efficiency,put forward the regional total annual runoff control overall goal and based on this proposed the sunken green space scale,set up comprehensive evaluation system,evaluate the effectiveness and sustainability of each program.The main results obtained are as follows:（1）Based on the analysis of the characteristics of stagnant rainwater storage in the sunken green space in hilly area,the quantitative calculation of the sunken green space is conducted around the runoff control efficiency of the sunken green space.A school in Hefei,a typical hilly area,is selected as the research object,set the total annual runoff control rates are 75%,80%,85%,and the corresponding design rainfall,rainfall duration of rainfall runoff and set 2 hours are sunken green space lag under storage.The results show that there are different depths（0.1m～0.3m）and area ratio（5%-25%）of green space in different regions,and the lower limit of soil infiltration rates are 1.16×10-4cm/s～4.03×10-3cm/s.（2）The SWMM model of the drainage system in the study area is constructed,and the comprehensive runoff coefficient method is used to verify the model,which proves that the model has good accuracy and good applicability to the study area.The preliminary transformation of the sunken green space in the study area is carried out,and the relevant data of quantitative calculation are applied to the SWMM model to simulate the rainfall process in different return periods of 2 hours in the study area.The results show that after the sunken green space is reconstructed,the rainfall characteristic values in the study area decreased,and the reduction rates of total runoff are30.05%～46.42%.The peak runoff reduction rates of the discharge outlet are14.71%～41.86%,and the reduction rates of pollutants are 35.78%～62.07%.（3）Combined with relevant requirements,the reconstruction proportion of sunken green space based on the overall goal of annual runoff total control rate is proposed,and the evaluation system of sunken green space is constructed by using fuzzy comprehensive evaluation method with subjective and objective weights,and the efficiency sustainability of its cumulative operation stage is explored and analyzed.The results show that the comprehensive evaluation values of sunken green space are 1.889,2.172 and 2.516 respectively in the three stages of cumulative operation for 10 years,20 years and 40 years,and the corresponding grade ranges are good,good and medium respectively.The overall sustainability of the research system was good. |
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