Study On The Runoff Generation And Flood Calculation Of Beijing Small Watershed

Beijing is located in the northwest of North China plain. With both plain andmountainous terrain, Beijing has a complextopography.In addition, the rainfall ofBeijing usually concentrated in summer,and the duration is short but intensity is muchhigh. Storm flood in Beijing has occurred frequently in history and brought seriousdisaster to the city. In recent years, several storm flood disasters occurred in Beijingmade people pay more attention to flood control in Beijing city.In recent years, Beijing proposed "valley economy" development model,whichtries to make integrated development planning of environment, landscape, villages andindustries in Beijing mountainous area, build a variety of industrial belt in Beijingmountainous area,and to develop the regional economy.This development model willsurely be subject to various restrictions like geographical and climatic conditions.Thevalley is highly exposed to the threat of flash floods, mudslides and other naturaldisasters. Currently, Beijing stilllacks a citywide mountain valley economydevelopment plan and a guidance of strong operability.One purpose of this paper is to study the Beijing Small Watershed Runoffcharacteristics and influencing factors. The main tasks include: Beijing Historical floodsand mountain flood characteristics analysis, typical small watershed runoff andgeological surveys,small watershed flood investigationafter Beijing2012"721"rainstorm Flood, and Beijing small watershed slope runoff experimentdataanalysis.Through field surveys and data analysis, found that Beijing’s small watershedrainfall runoff is related to lithology. Intrusive rocks, sedimentary rocks andmetamorphic rocks have different impact in watershed runoff generation. Of the3kindsof rocks, intrusive rocks lead to the minimum rainfall infiltration loss, while thesedimentary rocks cause maximum infiltration loss. Mostly small watershedsin intrusiverocksarea have perennial runoff, on the contrary,watersheds in sedimentary rocks areausually do not have perennial runoff and are difficult to produce rainfall runoff.Thepaper also summarized the flood calculation methods of Beijing small watershed:rational formula and improved rational formula. By fitting each parameter curve intoformula, parameters’ calculation becomes convenient and easy. Meanwhile, used the rainfall and runoff data of “721” storm flood to modify the calculation formula ofrainfall loss parameter, compared the corrected result with the measured ones. Themodification of parameter with only one rainfall data is not completely accurate.Therefore, to improve the hydrological monitoring network of Beijing small watershedto collect more hydrological data is very important and urgent.