Research On The Effect Of Rainwater Runoff Regulation Of Urban Road Ecological Bioswale Based On Planned Land

With the development of urban construction in China,the concept of sponge city is gradually applied in the process of urban planning.However,due to the different proportions of roofing,roads and green space in different urban planning land,there is also a large difference in rainfall runoff and runoff pollution.In this study,the sampling and analysis of rainfall and runoff pollution from different planned land are used to study the characteristics and laws of runoff pollution from different planned land.The experimental study is to study the reduction rate of runoff and the average removal rate of runoff pollution from ecological ditch.The effects of bioswale on the regulation of runoff and peak flow reduction in different planned uses were analyzed.The effect of road bioswale on reducing runoff pollution load was analyzed.Finally,an urban SWMM model was established to analyze the impact of road bioswale on urban water environment.The main findings are as follows:（1）By monitoring the three typical rainfall areas from July 2018 to June 2019 with five typical rainfalls,the differences between the runoff pollution of different planned land were studied,and there was a significant difference between the early and middle runoff pollution.Initial rainfall runoff concentrations of various pollutants in the water quality is much higher than in the late runoff,runoff pollution there are significant differences between different land use planning.（2）Adopt the Chinese experiment of designing road ecological ditch improved by large-grain ceramsite to study the relevant parameters of ecological ditch reducing water volume under rainfall conditions at different recurrence periods,and under different influent water quality concentration gradients,ecological ditch can pollute runoff The removal rates of COD,TN,NH₃-N,TP and comprehensive pollutants are about 40.13～73.12%,29.06～63.82%,10.92～63.88%,53.75～84.98%,38.29～61.52%,respectively.（3）Establish SWMM model based on the relevant parameters of different planned land use,and study the relevant parameters such as the comprehensive runoff coefficient,surface infiltration,surface runoff of different planned land use under the conditions of three rainfall recurrence periods（1a,3a,5a）,By simulating the runoff pollution load generated by different planned lands,the total pollutant load generated by different planned lands is ranked as follows:municipal roads>storage land>cultural and entertainment land>commercial and financial land>administrative office land>residential land>teaching and research land>public green land.The proportion of roads in the planned land has a greater impact on the total pollutant load.（4）Through field investigation and analysis of different planned lands,the proportion of road bioswale that can be reconstructed in different planned lands is also different.The type with a larger proportion of bioswale renovation,the higher the peak runoff and pollution load reduction rate of the planned land type.The reformable ratio has certain limitations,but the total amount of pollutant pollution load still has a reducing effect.The reduction rate of the total pollutant pollution load of the planned land with a transformation ratio of 5%,10%,and 20%is above 20%,30%,and 50%,respectively.（5）Taking Weiyang District of Xi’an as the research object,the SWMM model was established,and the changes of urban hydrological and water quality related parameters before and after the addition of road bioswale were compared and analyzed.The amount of reduction,the reduction rate of pollutant pollution load and the change of pollution load reduction rate.Before and after adding road bioswale,the urban water environment can be significantly improved.Under the rain conditions of 1a,3a,and 5a,the peak flow was reduced by 3.343 m3/s,2.985 m3/s,and 3.026 m3/s.The peak flow time was postponed by 3min,3min,and 5min,respectively,the reduction rate of the water quality pollution load（COD,TN,NH₃-N,and TP）showed a decreasing trend with the increase of the renewal period.