Research On The Design Flood Of Small Watershed Empirical Formulas

In water conservancy engineering, flood control impact assessment for construction project and middle and small river harnessing planning,it usually need calculate design flood.But most of the small basins lack of actual measured flow series or the series data is short, it is impossible to calculate the design peak flow by frequency method directly. It can be calculated only by using indirect method. In order to solve the problem of calculating the design peak flow of ungauged basins in Huangshan City, based on "Anhui Rainstorm Parameters Study" project, this paper analyzes the flood cause and flood characteristics of Huangshan City by taking the empirical formulas of the basin of 10～1000km2 area as the research object, selects a few typical hydro logic stations in research scope, samples observation discharge data by annual maximum method, fits curve and does frequency analysis by using Pearson Type Ⅲ Distribution, and obtains the frequency of 1% 2%,5%,10% of the design peak flow. Regard the main factors effecting the design peak flow as the starting point,this paper uses regional regression analysis, establishes empirical formulas of district characteristics combining design peak flow with dependable rainfall, basin area, basin shape factor, the river slope and river length taken as a composition of empirical formula factors at different frequencies, uses SPSS software to calculate the parameters of the empirical formulas. Compared the results calculated by frequency method and the empirical formulas, the results of empirical formulas have relatively small errors. And compare them with the empirical formulas in Huangshan Hydrological Manual, it shows that he empirical formulas in this paper have relatively smaller errors on the whole and the calculation results are more reliable.Apply empirical formulas obtained to practical and compare them with the empirical formulas in Huangshan Hydrological Manual and "84" approach,which show that the empirical formulas in this paper have stronger timeliness, use longer data series, more fit the actual case, render convenient calculation and can be available for reference use in calculating design flood in ungauged small basins of Huangshan City.