Research On Refined Hydrological Simulation And LID Layout Based On SWMM

In recent years,affected by urbanization and global extreme climate,urban waterlogging disasters occur frequently,which has seriously affected the daily life of our people.Rainstorm and flood simulation can provide an important support tool for the design and management of urban drainage system,and simulate and evaluate the rain flood state under different rainfall scenarios.Although the current rainfall flood simulation can realize the calculation of rainfall runoff and confluence,the traditional hydrological characterization method is relatively broad,and the catchment segmentation and hydrological calculation method is relatively simple,which can not accurately reflect the attribute of regional underlying surface and guide the spatial layout and optimal solution of lid measures.Therefore,a refined hydrological simulation is constructed,and how to improve the segmentation and characterization of catchment area based on land use description is proposed,so as to improve the accuracy of the model and guide the layout of LID.In this study,Hohhot a area is taken as the research area,and the refined rain flood model is constructed.Through the comparative analysis with the conventional hydrological characterization and response,the impact on lid layout scheme is solved,and the runoff and node overflow of the undeveloped area and the developed area after lid are quantified.The main research results are as follows:(1)With the help of GIS and SWMM,a refined hydrological simulation method is proposed to analyze the differences between the conventional and refined storm flood models.The results show that the total runoff,peak runoff and total overflow of the refined rainfall flood model in each rainfall return period are less than those of the conventional rainfall flood model.The hydrological characterization of the two models has less impact on the catchment area with more runoff.With the increase of rainfall return period,the impact of different hydrological characterization of the two models on runoff response is decreasing.(2)The results of LID layout show that the runoff control effect of LID layout in the direct impervious area(DCIA)is the best.Because the area of DCIA in the sub catchment decreases and the proportion of the corresponding indirect impervious area(ICIA)in the total impervious area increases after the LID layout in DCIA,the runoff generated in the impervious area increases when it flows to the drainage node,and the runoff through the permeable area increases when it flows to the drainage node.Therefore,the best runoff control effect is to set LID in DCIA.(3)Based on the refined hydrological simulation,the runoff response of the model before and after lid development was analyzed.Under the rainfall return periods of 1 year,2years,5 years,10 years and 15 years,the total runoff decreased by 55.81%,50.35%,42.76%,37.64% and 35.13%,the peak runoff decreased by 19.84%,15.93%,12.99%,9.68 and6.83%,and the runoff coefficient decreased by 0.33,0.32,0.30 and 0.27 respectively 26,showing a decreasing trend.Before development,the number of overflow nodes in each return period was 15,28,35,39 and 42 respectively.After LID development,there was no node overflow phenomenon in the study area when the rainfall return period was 10 years.The LID combination of Green Roof,Biological Detention Pool and Rainwater Garden can make full use of the living area space and has a good effect of rainwater control.