Calculation Of Critical Rainfall For Mountain Flood Disasters In Small Watershed And Analysis Of Its Influencing Factors

Mountain torrents,as a natural disaster,are the main hazard causing species in China.The Ministry of Water Resources,the Ministry of Land and Resources,and the China Meteorological Administration are very concerned about this.For recent years they’ve been complied two books of work such as the National Program for the Prevention and Control of Mountain Torrents and the Plan of National Project for the Prevention and Control of Mountain Torrent(2013-2015),and carried out a large-scale of analysis and evaluations in the whole country.Critical rainfall of the mountain flood disasters in small watershed,the designed storm,designed flood,the relationship between water flow rate calculation,calculation method and parameters selection is affected by the subjective or objective factors,there is a deviation so that the critical rainfall of the calculated value.At present,it is a hot topic to study the influential factors of critical rainfall.In the process of critical rainfall calculation,some factors will influence the critical rainfall value.In this paper,Hydraulic method was chosen to calculate the critical rainfall.By considering the influence of some factors,a reasonable critical rainfall range was determined.A method for predicting the critical rainfall of disaster prevention objects in areas without measured data is proposed.The specific research is as follows:(1)The Study of Calculation Method and Influential Factors on small watershed’s critical rainfall: In this paper,the rainfall runoff curve interpolation method is used to calculate the critical rainfall.Based on the flood calculation and the design of rain type,rain type Huff were calculated,and the results had been compared and analyzed;Based on the design of rain type,by changing the parameter value,analyzed the value of runoff parameters on critical rainfall;analysis in the same way on the roughness values of critical rainfall.The reasonable threshold range of critical rainfall is discussed.(2)Prediction of Critical Rainfall without Measured Data for disaster prevention: The index system of the critical rainfall of mountain torrents in small watershed was established by synthesizing the variable factors and determining factors of the critical rainfall.Based on the analysis and evaluation,a regression support vector machine model was established,and the corresponding relationship between each factor and the critical rainfall value was established according to the "dark box theory".According to the same topographic and landform conditions and the same mechanism of runoff generation and confluence,index value of the influence factor can be input to forecast the critical rainfall value in the area without measured data.In this paper,161 disaster prevention objects in Xinxian County were selected as the experiment set,10 disaster prevention objects were selected as the test group.The feasibility and accuracy of the method were determined by comparing the error between the predicted critical rainfall value and the critical rainfall value calculated by the production and confluence.The results show that this method is feasible.It can be used as a simple method to estimate the critical rainfall value in areas without measured data.