Rainstorm Waterlogging Simulation And Climate Risk Assessment Research Of Nanchang City

The research is based upon Nanchang City and cutting edge issues such as formation mechanism, mathematical simulation, risk evaluation, supervision and warning system for urban waterlogging have been studied by adopting comprehensively relevant scientific theories such as hydrology, weather and geographic information system etc. In order to decrease the loss of urban rainstorm and waterlogging, urban geographic information, drainage network, live monitoring data of rainfall and rainfall forecast materials have been fully taken advantage of for the research. Urban rainstorm and waterlogging stimulation model of Nanchang, which is based upon the rainfall monitoring and forecast platform in the meteorological department, has been established that has improved the overall level of urban rainstorm and waterlogging monitoring, forecast and disaster risk evaluation. Further more, according to per day and per hour precipitation, the waterlogging simulation model has been creatively utilized in waterlogging risk evaluation in Nanchang. Based on the model, the critical precipitation of the waterlogging has been calculated. So this model can be used in the urban waterlogging forecast system, as a new method.The main research findings and conclusion of this paper is as follows:1. According to the observation data from1961, influenced by global warming, Nanchang, the same as other cities, the temperature has obviously increased by1.1℃from1961. The warming rate is about0.23℃/10a. The annual precipitation doesn’t change a lot, but the rainy day is decrease. Specially, the sprinkle days have obviously decreased. The moderate rainy days also decrease, while the heavy rainy days and rainstorm days increase. So under the background of climate change, the rain intense of Nanchang is increasing. The risk of waterlogging is also increasing.2. The heavy rain always happens in summer, so the waterlogging is also happens between March and September, mostly in May and June. If the rain is heavier than15mm/h, there should be waterlogging. The main reasons, which cause urban waterlogging, are climate change urban design, drain design, drain management and terrain.3. Utilizing19rainfall monitoring data in and surrounding the research area and comparing calculation errors of different spatial interpolation methods, we will know that quadric surface fitting is the best method that can be used to calculate grid cell surface rainfall in Nanchang.4. According to theory that rain drops to the ground, then becomes surface runoff and flows into drainage pipe, the calculation thinking of urban waterlogging is determined. First, calculate the initial depth of rain in the grid, then current flow on the grid channels and in drainage pipes and then water level in the grid the next moment. Mathematical models of waterlogging simulation have been determined, including calculation model of rainwater effective flow in each grid, dividing the grid in to land grid and watercourse grid according to surface features, flow calculation models of watercourse channels, land channels and land-watercourse channels according to the relations between bordering grids, calculation model of land grid drainage flow including drainage pipes and calculation model of ponding etc.5. According to urban surface ponding converging process, calibration method of impermeable area percentage and roughness coefficient could be determined.6. By using actually measured depth data for key waterlogging sections and analyzing waterlogging depth and level errors, the conclusion of similar simulation results and actual situation is reached. For same important sections, detailed analysis is conducted for initial rainfall intensity of waterlogging and time of highest waterlogging depth and recession time, providing the basis for urban drainage pipe network improvement.7. For cutting-edge issues of disaster risk assessment, we proposed the city waterlogging risk assessment techniques and methods. By using the history precipitation data, we can testify and adjust the simulation waterlogging model. By using this model, we will get the frequency of different levels waterlogging disasters in different sections in Nanchang and the waterlogging-risk distribution map of Nanchang city. So we can give same advices to the mapping and transforming of the urban drainage network.8. Concept of critical precipitation of torrential flood and geological disaster warning is introduced. The rainfall intensity of mild, moderate and severe waterlogging is defined as critical precipitation. And critical rainfall of different waterlogging levels is calculated, providing new methods for urban waterlogging warning serve.9. Waterlogging disaster warning platform in Nanchang has been developed. Cutting edge issues such as formation mechanism, mathematical simulation, risk evaluation, supervision and warning for urban waterlogging have been studied by adopting comprehensively relevant scientific theories such as hydrology, weather and geography etc. And urban geographic information, drainage network, live monitoring data of rainfall and rainfall forecast materials have been fully taken advantage of for the research and development of urban rainstorm and waterlogging stimulation model and rainstorm and waterlogging warning system to realize mathematical simulation for rainstorm and waterlogging in Nanchang City. And research results with practical value, software copyright have been gained for integrated innovation.