Study On The Design Of Rainwater System In Building District Based On The Concept Of Low Impact Development

In recent years,with the rapid development of my country's urbanization process,the urbanization rate has gradually increased.In the traditional gray urban development model,a lot of impervious ground is used,so that the amount of rainwater seeping up and down on the ground is reduced.At the same time,the reduction of the infiltration volume leads to the gradual reduction of groundwater recharge,which seriously affects the groundwater system,and the water resources are increasingly tight,causing unnecessary waste.The SWMM model was constructed by collecting the data of meteorological conditions,topography,morphological,hydrologist,drainage pipe network and urban flood control of a building district in Xixian new area.Using the modified Morris method,the established model was subjected to sensitivity analysis on 13 parameters of the model,and finally 8 parameters were selected.The 8 parameters were calibrated using the universal likelihood uncertainty assessment method.The NSE coefficient method was used to compare the simulated value of the model with the monitored value,and verified that the NSE of the three rainfalls were all greater than 0.6,which indicated that the model simulation after the parameter calibration was highly consistent with the actual simulation.The model was suitable for this site.According to the results of mode:For a particular development state,the runoff curve of different recurrence periods is approximately the same.With the increase of recurrence period,the runoff also increases;The maximum runoff time in each recurrence period: Natural State > Low Impact Development > traditional development;Compared with traditional development,the maximum runoff time of low impact development will be delayed;With the increase of rainfall recurrence period,the time to reach the maximum runoff in low-impact development and natural condition decreases gradually;In each recurrence period,it reaches the maximum:Traditional Development > Low-impact Development > Natural State;Low-impact development greatly reduced the peak runoff under the traditional development,and the average peak runoff reduction rate was 57% under the five-year recurrence period;Under the condition of small return period,the peak value of runoff under low impact development is little different from that under natural condition.A comparison of different development modes shows that the surface runoff in the 2a recurrence period and the 5a recurrence period is reduced by 60% and 64% in LID mode compared with that in the traditional development mode.10 a recurrence period: low-impact development reduced surface runoff by 65% compared with traditional development;30a recurrence period: the surface runoff of low-impact development was reduced by 63% compared with traditional development;50arecurrence period: low impact development reduced surface runoff by 61% relative to conventional development.The research results of this paper can reflect that compared with the traditional grey development model,the site development under the guidance of the low-impact development model can effectively control the surface runoff and extend rainwater peak time.