Urban Storm Simulation Study

In recent years,due to the acceleration of climate change and urbanization,the storm runoff conditions in urban areas have changed,the total amount of surface runoff has increased,and the peak time has been earlier;the direct or indirect losses caused by urban storms and flood disasters have been increasing.At the same time,it brings great challenges to urban stormwater pipe networks.Scientific management decisions are widely evaluated by means of models.Shanghai's location at the mouth of the Yangtze River is representative of a typical coastal city.Heavy rain disasters have occurred in this region.Therefore,based on the literature data and data obtained,this paper simulates storm events under different return periods.Using the MIKE URBNA model and the improved SCS model as a means to effectively divide and connect sub-watersheds and determine rainfall Parameter boundary conditions:Connect the production flow model and the pipe flow model to test the ability of the study area to withstand rainstorm to find out the distribution of easy points,and use the Shanghai downtown area(former Jing'an District)as an example to conduct empirical research.Mainly achieved the following research results:1.Improve the SCS model to simulate pipe network overflow scenarios under different return periods.The prominent feature of the overflow distribution is that the diffuse flow has a wide range,the depth of submerged depth is less than 0.2cm,and it is concentrated on both sides of the road.The comparative analysis was made on the area of city water,the number of node overflow,the flow rate of the pipe network,and the maximum area of water collected in the subcatchment area under different return periods.The results showed that:the urban water area and the number of nodes overflowed with the return period.With the increase,the area of stagnant water increased by nearly 29.67 times,and the growth rate of node overflow was 63.66%.The flow rate of the pipe network and the amount of water accumulated in the subcatchment area show different characteristics at different return periods.In the case of 2 years,the flow rate of the pipe network was relatively slow,and the maximum pipe network flow rate was 23.42 m~3/s.In the 10-year scenario,the flow rate of the pipe network increased,and the maximum pipe network flow rate was 25.63m~3/s.During the rainfall process,the sub-water collection areas have different levels of water accumulation.In the case of two years,the maximum amount of accumulated water in the sub-water catchment area is 952.47m~3;in the case of 10 years,the largest sub-water catchment area The total amount of accumulated water is 1595.93m~3.2.Studying the MIKE URBAN model to simulate pipe network overflow under different return periods.The characteristics of overflow distribution are concentrated near the road intersection.In the same scenario,the flow rates of the same pipe section at different times are different,and the time at which the flow rate peaks occur in different pipe sections is not necessarily the same.A comparative analysis of the total amount of accumulated water in the study area,node overflow volume,surface production flow,and underground pipe network flow under different return periods revealed that the total amount of accumulated water in the area,the number of node overflows,and the surface production flow The flow of underground pipe network increases with the increase of return period,the growth rate of total water volume is68%,the growth rate of node overflow volume is as high as 89.46%,the growth rate of surface production flow rate is 66.67%,underground pipe network The growth rate of traffic is 75.58%.With the increase of the return period,the time at which the peak of the flow velocity occurs in the same pipe section is not necessarily the same.The ratio of surface water accumulation to underground stormwater pipe network distribution at different return periods was 70.94%and 29.06%,respectively.Based on the dynamic data of total rainfall-surface production flow-underground pipe network flow,it can be seen that the surface production flow and underground pipe network flow are normally distributed with time,and the peaks of both are located in the latter half of the rainfall process.3.Comparing the two simulation results,the results show that:Compared with the MIKE URBAN model,the precision of the overflow distribution range of the improved SCS model is higher;the number of overflow nodes of the SCS model is improved with the increase of the return period.The result is too large.In the same return period,the simulation results of the two model pipe networks tend to be consistent.Due to the formation process,causes and complexities of urban floods,this article is limited to explain the urban flood phenomenon from the perspective of surface runoff and underground stormwater pipe network.Although it provides a certain basis for government decision-making,in reality,relevant research needs to be carried out according to regional characteristics..There are some deficiencies in the study of this article.First of all,the model of the pipe network considered in the model used in the text is more idealized.It does not take into account the influence of outside interference factors such as the leakage of the pipe network and the occurrence of congestion.Secondly,1h rainfall event was selected in this paper.Lack of long-term precipitation data and runoff depth data was used for further study.Finally,the parameters in this paper are empirical values,and a large number of measured depth data are needed to further enhance the reliability of the results.