Research On The Retrofit Of Urban Drainage System Based On Low Impact Development Technology

As the fast growth of urban population and quickly expansion of the urbanization, urban areas have increased lots of impervious surface, which presenting a negative impact on the natural hydrological cycle, reducing infiltration volume of the surface rainwater, accelerating the collection process of runoff, resulting in a rapid increase in total runoff volume in the urban area. As the result, the risk of urban flooding keeps rising dramatically. Especially, when it is come to the high intensified rainfall event, due to the limited designed capacity of drainage system, the existing drainage pipe cannot reduce the peak effectively. So the overflow shows in the majority urban area, leading to the occurrence of urban flooding.In this dissertation, aiming at solving the currently serious urban flooding in the most of city in China, proposed a entirely new approach which named low impact development (LID) to retrofit the existing drainage system. Through the imitation of natural hydrological cycle system including the process of infiltration, evaporation, retention and storage for stormwater, in term of source reduction, process controlling, end-of-pipe treatment, achieved an effective reduction in the total runoff volume, preventing the occurrence of urban flooding, promoting the replenishment of groundwater, restoring urban natural cycle, adjusting the rising temperatures in the urban heat island through evaporation, mitigating the global climate change and even minimizing the energy demanding for house heating and cooling. The main research content will be listed as follow:Firstly, we developed LID theory study which based on the literature review. Secondly, we built an actually project hydrological and hydraulic model based on SWMM, to access the regional hydrologic and hydraulic situation of the site respectively. By comparison of the output data, demonstrated the formation mechanism of urban flooding. Then identify the main impact factor on urban flooding by loading different periods of simulated rainfall events on the model. Additionally, proposed the formation process theory of overflow through the hydraulic simulation. Besides, based on the simulation results, considering the principle of selection LID-BMPs, land use and zoning, proposed a retrofit strategy based on LID. Finally, through the calibration of SWMM, demonstrate the effectiveness of LID, Providing some references for the LID applications.