Urban Rainstorm Waterlogging Simulation Research Based On Scenario Analysis

In the context of the global complex climate change and urbanization accelerating development, the urban extreme rainstorm weather events occurred frequently, which have seriously threatened people's normal life and security. The simulation research of urban rainstorm waterlogging process by different scenarios, which provides important scientific basis for the relevant departments to take effective urban storm waterlogging prevention measures and flood discharge.The paper takes a part of the Beilin District of Xi'an City as the research object, obtains the terrain data of the research area is analysed by using ArcGIS software, and draws the drainage network generalization graph.Based on the SWMM model to establish the regional urban waterlogging simulation model, several different scenarios conditions are designed for the urban waterlogging process simulation, analyzing the situation of flow change process and water accumulation of urban waterlogging in different situations, and providing decision-making service for the establishment of urban waterlogging coping mechanism. The main results of this paper are as follows:(1) The urban rainstorm waterlogging model is suitable for the practical research area was established in the paper. The way is to get the basic data through ArcGIS software analysis,field investigation and the distribution map of drainage network.Based on the SWMM model,the waterlogging simulation model was established. Comparing with the results of the rainfall simulation occurs once a year and the water accumulation in the actual area roads, the section of waterlogging water is basically consistent with the actual situation, with the good rationality of model is verified.(2) Urban waterlogging simulation in research area based on scenario analysis. Design of different precipitation return periods, different rainfall patterns and different urbanization levels for three scenarios in the paper, and the different return periods includes five forms, which are:0.5a, 1a, 2a, 5a and 10a. From the perspective of different precipitation return period, the runoff coefficient displays significant increasing trend, with the precipitation recurrence period is increased, and the risk of waterlogging is also increased. The outlet flow process in different precipitation return period is analyzed, the longer the return period and the larger the peak flow,with the prolonged duration. Select three types the rainfall peak coefficient r for 0.3, 0.4 and 0.5 in the different scenarios of the Chicago rain patterns, the results show that the rainfall peak coefficient is larger will arouse an increase of the runoff coefficient. The same precipitation return period, the pipeline overload situation for different three rainfall patterns is basically consistent. The increasing rates of urbanization level and runoff coefficient are not so much different in the different urbanization level.(3) Simulation analysis of water accumulation points for different precipitation return peri-ods scenarios. Simulating the overflow condition of pipeline network nodes, under four ways return period: 1a, 2a, 5a and 10a, and the overflow of the nodes for scenario in five-years return period is more, even higher return period more larger. From the analysis of the flow and depth distribution of water accumulation points, urban waterlogging water is the most serious in the main road section. Selecting the typical accumulation point of the major roads which have a water accumulation, the analysis found that drainage capacity is related to the maximum flow of the pipeline and the duration, can take appropriate measures to improve the pipe network.(4) The Visualization of urban waterlogging simulation process is based on comprehensive integrated platform. With the knowledge graph visualization, business component and comprehensive integrated platform as technical support, by drawing research area drainage network knowledge map, realizing the multiple objects information online display, drawing related flow graph, providing decision service for users and drawing relevant flow curve graph.