Evaluation Of Rainwater Runoff Management Effects For Typical Projects Of Road And Park In Sponge City

In recent years,Chinese cities were growing rapidly and big cities and megalopolis were established one after another.The original infrastructure construction had been difficult to meet the living requirements of residents,which led to the phenomenon of urban waterlogging and runoff pollution.For such problems,the state took the lead in building sponge cities in some typical cities and sponge city construction in some areas had begun to take shape.In that case,effectiveness evaluation of rainwater storage function and non-point source pollution has became the research hotspot in recent years.In this research,the typical sponge city project?road and park?in the sponge city construction demonstration area of a south city were the object of study.The runoff and its pollution of sponge roads and parks were studied by field test,SWMM model simulation and other technical means.The results were shown in below.The permeable pavement in road was less efficient in rainwater runoff management.After 9 months,the water permeability decreased by about 30%.The initial rain treatment facility had a high reduction efficiency for SS and COD?up to 100%?,while the removal efficiency for TN was only 20%-30%.The reduction efficiency decreased with the increase of rainfall intensity.The runoff control rate of bioretention for moderate and heavy rain could reach 65-80%,and the pollutant control law was similar to that of the initial rain treatment facility.The removal efficiency of TN in heavy rain was only 20%.With the increase of rainfall intensity from light rain to heavy rain,the drainage capacity of kerbstone decreased from 0.5 m³/s to 0.2 m³/s.The total annual runoff control rate of depressed green in the park was up to 75%.The control rate of COD could reach 65-80%,and TP was about 50%.Similar to the permeable pavement in road,permeable pavement in park could reduce the rainwater runoff to a certain extent,but with the increase of service time,the perviousness decreased.The reduction rate of SS in the wet pond in the park was more than 60%,and the volume capture ratio of rainfall was more than 70%.According to the actual test results,the volume capture ratio of rainfall in the road area was 59.4%,the pollution control rate was 68.7%,the volume capture ratio of rainfall in the park area was 80.6%,and the pollution control rate was 81.1%.SWMM model was used to model the volume capture ratio of annual rainfall,and 7 rainfall data were used to calibrate the model.The E_NS value was greater than 0.60,and the coefficient of R² was greater than 0.80.The calibration effect was better.Through the simulation of SWMM model,the volume capture ratio of annual rainfall in the road was60.5%,and that in the park was 82.4%,which was not much different from the measured value.The optimization results of runoff technical parameters showed that the road runoff coefficient was high and the volume capture ratio of annual rainfall was better than the expected value.The road and the park had no rainwater utilization facilities,so there was no utilization rate of rainy water resources.In terms of runoff pollution parameters,the annual runoff pollution control rate of the road was higher than that required by the sponge road construction guide.The reduction rate of the initial storm water pollution load of the road could reach 65.43%,and the reduction rate of the initial storm water pollution load of the park could reach 83.28%.