Studies On Urban Short-Duration Rainstorm Intensity Formula Of Fujian Province

With the development of our country economy and the increase of the city area, the urban drainage design puts forward higher requirement The storm-runoff computation and the drainage-piping design in the urban drainage engineering are mostly based on urban short- duration rainstorm intensity formula Fuzhou and Xiamen of Fujian Province have the rainstorm intensity formula made in 1973, their practicality and veracity are hard to satisfy the planning and design of municipal engineering. To satisfy the demand of urban development, this item makes up the urban short-duration rainstorm intensity formula of 9 cities 65 towns of Fujian Province according to their observed rainstorm data. The research results of the program fill up the gap in the field of urban rainstorm study and are important to urban drainage system planning and management in Fujian Province.The accuracy of the rainstorm intensity formula relies on dependability of rainstorm formula data and rationality of the statistical method. In the studying of urban rainstorm formula, the frequency distribution of urban rainstorm must be checked to keep with the self-recording data, and the pattern of the rainstorm formula and the method of parameter optimization must be chosen. The former decides the dependability of the i-t-T data, the latter influences the regularity of i-t-T data which is made by frequency distribution.In this paper, three types of frequency distribution , Pearson type â…¢, Gumbel distribution and exponential distribution, which are often used to fit the urban rainstorm intensity formula are discussed and the statistical characteristics of exponential distribution is analyzed emphatically. The Pearson type â…¢ distribution is selected to be the urban rainstorm probability distribution by statistical significance test with the observed urban short-duration rainstorm data from 65 observatories in Fujian Province. The rainstorm intensity formula with three parameters is chosen to fit the urban rainstorm and the nonlinear parameter optimization technique is also used to estimate the parameters of the formulaThe 65 urban short-duration rainstorm intensity formulas of towns in Fujian Province are proposed, and the parameter spatial distribution regularities of the formulas are also analyzed here. The research results are important to urban planning of Fujian Province and can be used to city drainage engineering design.