Calculation And Synthesis Of Design Storm And Flood Parameters In Medium And Small Watersheds In Heavy Rain Areas In South China

Under the background of climate change,mountain torrents have become the key issue of flood control and disaster reduction.Due to the lack of sufficient hydrological stations and hydrological data,small and medium-sized watersheds have become flood-prone areas.The yield and confluence meter is the basis of all design rainstorm flood problems.In hydrological calculation,the measured rainstorm flood data are often used to reverse the instantaneous unit line and reasoning formula parameters,and the confluence model is nonlinear corrected by parameter synthesis.In this paper,taking the Caojiang River Basin in Guangdong Province as a typical study area,according to the measured runoff and rainfall data from 1967 to 2013,on the basis of analyzing the characteristics of rainstorm and flood,the variation characteristics of rainfall and runoff in Caojiang River Basin are analyzed,and its inherent change law is discussed.the main research contents and conclusions are as follows:(1)According to the measured rainfall and runoff data of Caojiang River Basin from 1957 to 2013,combined with wavelet analysis and Mann-Kendall trend analysis,the trend and periodic characteristics of the basin are analyzed.The results show that the trend change of multi-year precipitation series is not obvious,and there are significant periodic oscillations.Two probability distribution methods,P-Ⅲdistribution and generalized extreme value distribution,are adopted,and different parameter estimation methods of flood distribution function are compared.The results show that the estimation results of the generalized extreme distribution parameter estimation method and the maximum likelihood estimation method are more consistent with the actual situation,which provides a reference for the design flood formulation of the Caojiang River basin and the medium and small watersheds with the same characteristics.(2)The rainstorm flood with heavy rainfall and runoff after a long drought in Caojiang River Basin is selected,and the reasoning formula parameter m and comprehensive unit line parameter m1 are deduced respectively,and the relation curve between reasoning formula parameter m and net rain depth hR and flood peak discharge Qm is established.The relation curve between instantaneous unit line parameter m1 and rainfall intensity i is established.(3)51 experiments of precipitation and runoff under artificial control in the field were carried out,and combined with the measured flood data of the watershed,the effects of slope,vegetation cover,early soil water content and rainfall intensity were identified.the contribution of rainfall intensity,slope and early soil water content to precipitation infiltration was obtained by statistical analysis.The results show that topography and rainfall intensity are the main influencing factors,followed by soil water content and slope,while the influence of vegetation coverage is relatively small.Figure 24 table 15 reference 108...