| The rainstorm intensity formula is an important basis for the planning and design of urban rainfall drainage system,which directly related to the reasonable,effective,economic of the planning,design and construction of urban drainage system.In the process of Urbanization,the characteristics of heavy rainfall in the city also changed obviouslyly,rainstorm intensity formula as an important basis for the design of city drainage system,it dose not suitable to the development of the city.According to the national standard of the people's Republic of China "Code for design of outdoor wastewater engineering(GB50014-2006)(2014)",in the conditional region,the annual maximum method is used to replace the multiple sampling method to calculate the rainstorm intensity formula,at present,with the annual multiple sample method to calculate the rainstorm intensity formula is not corresponding and need to revision.Dongying city as an example,this work investigates the establishment of rainstorm intensity formula is studied.The study employs the data of the continuous rainfall autographic record from 1994 to 2014 of Dongying Meteorological Bureau,from 1983 to 2014 of Guangrao Meteorological Bureau,from 1980 to 2014 of Kenli Meteorology Bureau,respectively,using annual maximum value method is used to establish the statistical sample.By means of Pearson III distribution curve,Gumble distribution curve,exponential distribution curve fitting adjustment,the relationship between reappearing period,rainfall intensity and rainfall duration in Dongying is obtained,also is in Guangrao,Kenli.According to the value of the resulting P-i-t relationship,the least square method and the Gauss Newton method are used to calculate the parameters and calculate the mean square deviation of the rainstorm intensity formula,by analysis and comparison of average absolute mean variance and average relative variance,we recommend using the Pearson type III distribution curve to extend the data sample,using least square method to solve the parameters,and calculate the formula of rainstorm intensity.By calculating,the formula of single return period and the formula of any recurrence period in Dongying,Guangrao,Kenli are obtained,and the formula of rainstorm intensity is also obtained.According to the calculation results of Dongying,Guangrao,Kenli rainstorm intensity formula and the original rainstorm intensity formula in Dongying,the duration of the rainstorm intensity contrast,the results showed that there is a significant difference in the duration of the different.Through the testing of the accuracy of the new formula,taking into account the Dongying precipitation data does not meet “Technical Guidelines for Establishment of Intensity-Duration-Frequency Curve and Design Rainstorm Profile”,so,taking the precipitation observation data of Kenli instead of the data of Dongying station,the formula of rainstorm intensity is calculated as the rainstorm intensity formula of Dongying central city.The formula of rainstorm intensity in central city of Dongying is compared with that of the original rainstorm intensity formula,and draws a conclusion that the difference values of the calculated values of rainstorm intensity formula in different duration,different recurrence period are obtained.At the same time,compared with the rainstorm intensity formula in the surrounding cities of Weifang and Binzhou,it can be seen,Dongying city,each return period lasted 5min and 10 min rainstorm intensity slightly larger than Weifang and Binzhou,the other lasted basically consistent.The method of calculating rainstorm intensity formula for the city of Dongying is accurate and reliable,the method can also be used in other urban rainstorm intensity formula derivation. |
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