Research On The Application Of SWMM In The Planning Of Flood Drainage

In recent years, under the impact of global climate change, there have beenserious waterlogging disaster in many cities, which seriously harms to the socialmanagement, operation and daily life of the residents. For the issue, the Ministry ofHousing and Urban-Rural Development issued the "urban drainage (stormwater)waterlogging integrated planning framework", according to the requirements ofoutline, the Ningxiang regional central district should be able to effectively deal withthe stormwater of no less than20-years recurrence interval, and for the pipes ofcatchment area of over two square kilometers, it is recommended to use the hydraulicmodel to check storm sewer drainage planning scheme.This study uses EPA SWMM (Storm Water Management Model) softwaredeveloped by the U.S. as the primary research tool, Take Ningxiang for example,（1）Designning the rainfall of2-year recurrence interval by Chicago rainfallline method and simulating the rainfall and flood for the current drainage pipe, toverify the rationality of SMMM simulation by comparing the simulation results withthe current data; then using the Changsha latest storm intensity formula to redesignthe drainage pipe in special plans for drainage of rainwater before, and to determinethe size of the relevant tube drainage by2-year recurrence interval.（2）Using SWMM to check the planning rainfall system for2-year recurrenceinterval, simulation results show that when P=2a, in addition to DY4-4node appearsa small amount of water, the rainfall system by reasoning formula method can basiclymeet the requirement of drainage for the rainstorm of2-year recurrence interval, andthe rationality of SMMM simulation is verified.（3）designing the rainfall of20-year recurrence interval by Chicago rainfallline method again, and using the SWMM model to simulate rainwater drainage pipedetermined by the formula reasoning method above, when the tube drainage waterline is over ground elevation line, the overflow and formation of ground water occurs;simulating the flow state in tube drainage again through additional rainwater storagetank in the rainfall of20-year recurrence interval. With principle of no groundoverflow to determine the appropriate volume of rainwater storage tank, so that theplanning pipe drainage can meet the requirement of the rainfall of20-year recurrenceinterval. （4）Urbanization has seriously damaged the impermeability of underlyingsurface, which directly results in the greatly increasing of stormwater runoff andpeak flows. It is proved to be not enough that improving the rainstorm recurrenceinterval of drainage pipe simply, which not only costs too much for construction, butalso for the limited site conditions, it is difficult to transform the existing pipenetwork in the old town of city. We can use the stormwater management that isclose to the natural way, and try not immediately to discharge urban stormwater intopipes and the river, but to use of existing depressions and water body for scatteredaccumulation and preliminary purification, which stores the entered rainwater briefly,then slowly discharge it into the river.（5）According to the actual situation of the Ningxiang downtown, we shouldmake use of the waste ground into a storage pool. On the condition of rainfall of20-year recurrence interval, the discharged flow of rainwater for bigger flow decreasesgreatly after the storage pool, which have played an important role in preventwaterlogging. To make use of depressions for backwater or build storage pool canreduce the size and cost of the drain pipe canal in the drainage system, it is anengineering measure that can effectively improve the ability of wate drainage of thecurrent urban drainage system.