Evaluation Of Rainwater Runoff Control Effect In Sponge City Construction

With the acceleration of urbanization process,the water crisis characterized by water shortage and water pollution has become more and more serious,and the concept of sponge city has emerged in response to the proper time and conditions.In recent years,the construction of sponge cities has made rapid progress in China,but there are some problems in the planning and management of sponge cities due to the insufficient understanding of the basic theory of Urbanization.In order to assess the rationality of sponge city construction and build sponge city more scientifically,this study takes Xinglongshan Campus of Shandong University(X region),one of the pilot area of sponge city construction in Jinan,as the main research object,and the farming area(J region)and the urban area(W region)with no low impact development(LID)measures in Jinan are took as the reference object.Field test and hydrological numerical simulation are took as the main means to evaluate the effects of sponge city construction on rainfall runoff.In view of the problems existing in the operation of LID measures,reasonable solutions are put forward to provide experience support for the healthy development of sponge city construction in China.The main research results are as follows.1)Through the monitoring and analysis of water quality in research area,the impact of urbanization on water quality and sponge city construction on runoff water quality was preliminarily evaluated.According to the results of water quality monitoring in J region,the water body is lightly polluted by organic pollutants and has strong self-purification ability compared with the urban water.Comparing the monitoring results of runoff water quality in W and X regions,the water quality of runoff in X region has been improved significantly due to the sponge city construction.The results of simulated runoff test in X region show that permeable pavement,bio-retention cell and rain gardens all have significant improvement effects on runoff quality.The bio-retention cell and rain gardens have better improvement effect on total phosphorus,total nitrogen and ammonia nitrogen pollutants in runoff,and the permeable pavement has stronger ability to reduce the concentration of suspended solids.2)SWMM numerical simulation technology was used to evaluate the impact of urbanization and sponge city construction on the relationship between rainwater runoff.According to the numerical simulation results of rainfall runoff in J region under designed rainfall events,the runoff generatd in 24 hours is only from 22.8%to 33.41%of the rainfall,and the ratio that rainfall converted into runoff in J region is much lower than that in the urban area under the traditional fast drainage system.The numerical simulation results of rainfall runoff in X and W regions show that the construction of sponge city in Area X meets the standard of Jinan sponge city construction,the total runoff control rate of experimental group in Area X is increased by 41.7%to 44.4%after the construction of sponge city under designed rainfall events,the peak discharge of each discharge outlet decreased by 5.4%to 87.9%,and the peak flow time was delayed by 1 to 20 minutes.3)SWMM numerical simulation technology was used to evaluate the effect of rainwater runoff control of various low-impact development measures in the study area.The numerical simulation results of LID measures on rainfall runoff control in X region show that total runoff control rate of rain gardens is higher than that of permeable pavement.With the increase of impermeable surface percentage treated by rain gardens and permeable pavement,the total rainfall runoff control rate increased,and the peak flow time of runoff is delayed to a certain extent.4)The management and maintenance scheme of LID measures is put forward due to the test analysis.The control effect on rainfall runoff of LID measures such as rain gardens,bio-retention cell and pervious pavement is weakening with the increase of service life.Therefore,regularly maintenance of LID measures is particularly important.Based on the experimental analysis,this paper puts forward a scheme to solve the silting problem of rain gardens,bio-retention cell and pervious pavement,so as to effectively guarantee the long-term healthy operation of sponge city.