Research On The Rainstorm Runoff Effect Under Urbanization And Measure Of Urban Rainwater Utilization Control Based On SWMM

Urbanization has greatly changed the climate and the composition of the underlying surface of the watershed, so that spatial and temporal distribution of rainfall and rainfall-runoff effect undergone in the watershed great change, these changes are closely related to the water circulation patterns, water use, rainfall-flood control of the watershed. Thus it brings the originally natural river channelization, the channelization has in turn exacerbated the impact of hydrological effect, which is the urbanization brought to the watershed. So it is necessary to study and simulate urban rainfall features and rainfall-runoff characteristics to explore the utilization and control measures of the urban rainwater resource.The article is based on the 61 years’precipitation observed dates of Xuancheng City from 1953 to 2013, using linear regression trend, Mann-Kendall trend test and the moving average method, analyses the trend of annual rainfall and flood season rainfall of Wanxihe River Basin, using double cumulative curve method, sequential clustering method and nonparametric M-K mutation test, analyses catastrophe point of annual rainfall and flood season rainfall of Wanxihe River Basin. Sort out the measured rainfall data for statistics, and analyses of the reappearing period and rainfall duration, get the distribution of urban rainstorm as the support and date basis for research of the rainfall-runoff effects in the urbanization. Representative rainfall stations series trend analysis shows that regional urbanization, land use change was less affected on rainfall in the nature of long duration, long-periodic scale, its impact is seen at the short duration, short-periodic rainfall sequence. Representative rainfall stations mutation site analysis showed that rainfall mutation site in time is 1990 and 2000, the results were in accordance with the city’s actual development history. Rain storm frequency and pattern of analysis shows that in 50 years, in 20 years appears rare rainstorm is still concentrated in the year prior to 1990, indicating that urbanization expansion has smaller storm impact on storm rainfall magnitude, by analysis of rain storm pattern followed, it shows that bimodal rain storm is most common in the research area.Reguard Xuancheng Wanxihe River Basin as a typical study area, according to the actual land data, remote sensing data and terrain information analyses the difference of the nature of the land before and after city development, understand the changes of land use patterns in different periods, and analyses the status of the study area urban drainage partition, combined with the natural hydrological district division, clarify the division of water produce and drainage of the whole study area, use the SWMM model to simulate the urban and natural rainfall-runoff. To compare the simulation results found the impact of urbanization on rainfall-runoff effect is very obvious, which has nonlinear variation.According to the actual floods calamity of the study area, combined with topography of the study area, propose 3 kinds of utilization and control measures, which are traditional storage tanks, low-impact development (LID) and "storage tanks+LID" respectively. Using SWMM model these 3 kinds of water resource control measures and watching the effects in the study area, provide useful suggestions for the study area rainwater control and utilization.