| The continuous acceleration of the process of urbanization has led to a series of urban problems.One of the problems is waterlogging.In order to effectively alleviate waterlogging disasters,the country has begun to vigorously advocate t he construction of sponge city.Urban green space is the main carrier of the construction of sponge city.In order to effectively solve the problem of insufficient water storage capacity of traditional green space and poor soil properties,this paper proposes to improve th e green space configuration in concave and stepped shapes,and use filling materials to improve the soil.The new method aims to enhance soil permeability,improve the ability to control rainwater runoff,and construct traditional green space into sponge-like green space.At the same time,a storm water management model(SWMM)was constructed on the basis of experimental test.The results of the model were tested and analyzed to make the model suitable for hydrological evaluation under experimental condition s.Then the model is applied to the actual research area,and a new method of constructing a comprehensive evaluation system framework is proposed,provid ing a reasonable reference for the planning and design of the sponge city.The main research contents and results are as follows:(1)The slope type green space was improved by concave type and ladder type,which can improve soil storage and permeability to a certain extent.The greater the depth of the depression or the greater the proportion of step transformation,the smaller the runoff coefficient of green space,and the better the improv ement effect on soil soil storage and permeability.The improvement effect is the best when the depression depth is 9cm or the step transformation ratio is 100%.(2)The permeability and storage of soil can be improved effectively when using zeolite,building waste material and gravel to fill the permeable column.The peak infiltration drainage rate and the infiltration drainage volume are significantly increased.Among three filling materials,zeolite has the best effect on improving soil permeability.(3)Use the Low Impact Development(LID)module in SWMM to construct the SWMM-LID model to simulate and model the hydrological process of the concave slope green space,the step slope green space and the permeable column,and perform the model.The parameters are calibrated so that the simulation results of the model roughly match the experimental test results.After the simulation is completed,check the fit of the model,and use the method of Morris to analyze the sensitivity of the model parameters.The results show that the model has high accuracy and is in good agreement with the measured results.Among the model parameters,soil hydraulic conductivity and soil porosity are the most sensitive to the total runoff.(4)Deploy the constructed LID module in the actual research area,analyze the reduction effect of different LID construction schemes on water quantity and quality,and calculate its economic cost.Research shows that LID can reduce the total amount of runoff,runoff coefficient,peak discharge and total SS to a certain extent,and can alleviate the accumulation of water at nodes.Among the different LID construction plans,the combination of vegetative swale,rain garden,and biological retention pond has the best effect in reducing water quantity and quality,but the total life cycle cost is the highest;while vegetative swale has the worst effect on water quantity and quality control,the total life cycle total cost is the lowest.(5)The total runoff reduction rate,the peak discharge reduction rate,the total SS reduction rate and the total life cycle cost are taken as evaluation indicators.The TOPSIS analysis method is used to comprehensively evaluate the performance of 7 LID construction projects,and the analytic hierarchy process is used to determine the weight coefficient of each evaluation indicator.The analysis results show that the combination scheme of rain garden and biological retention pond is the most ideal. |
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