Study On The Selection Of Histoical Date And Treatment Effect On Rainfall Intensity Formula

With the development of the city and the change of the climate in recent years,the urban waterlogging becomes more and more serious, causing a great threat to the people's life and property security. Our country put forward serious of measures such as constructing the Sponge City, improving the drainage standard and optimizing the design of pipe network in order to solve the urban waterlogging problem. These measures are all based on the precise storm intensity formula, however most cities in our country still use the storm intensity formula complied in the 1980 s. Because of the unperfect storm data statistical method, the outdated data processing technology,the less sample data and the large change of the climate, the formulas can't be well reflected urban storm patterns. Therefore our country starts the work on compiling storm intensity formula in large scale. The paper is on the background of storm intensity formula revisions of Ganzhou city program, using the storm data supported by the Climate Center of Jiangxi Province, researching the selection of historical data and processing method influencing on the calculation of storm intensity formula. The work has great theoretical significance and practical value to the compilation of storm intensity formula in our country. The main important work of the paper is as follows:(1) Analyzing the research status of storm intensity formula at home and abroad,introducing the theoretical basis of storm intensity formula compilation and the storm intensity computing system used in the paper.(2) In the compiling processing of storm intensity formula, it needs to judge and handle the extraordinary value existed in the historical storm data. The storm value in1961's 45 min to 180 min of Ganzhou city is judged to be the extraordinary value by the 3? method. There are three methods to deal with the extraordinary value: reserve it, delete all the value of the year, and replace it by the secondary value. By comprehensive analyzing the error of curve fitting, parameter precision calculated,the integrity and validity of the sample, the extraordinary value processing is chose to be replacing it by the secondary value.(3) Researching the selection method influencing on the storm intensity formula calculation. We compare the annual maximum method of new specification with the annual multiple selection method of old specification, finding that the return period of annual maximum method is larger than the annual multiple selection method to achieve the same storm value in a small return period. Therefore the return period standard needs to be improved when calculating the storm intensity formula based on the new specification and the security of the city drainage system is improved as well.We compare the storm intensity formula calculated by the data of 53 years with that by the data of 30 years based on the annual maximum method, finding that the storm value calculated by the 30 years data is large than that by the 53 years. Therefore the length of data selection should be based on the sample characteristics of local in the processing of selection.(4) We compare the storm intensity formula compiled by the data of 30 years and the annual maximum method with that used in Ganzhou city currently. The Xinfeng county Ganzhou city is used as an engineering research object to analyze.Through comparison and analysis, it is concluded that the design of storm sewer drainage flow, pipe diameter and flow velocity etc using old formula based on old specification are lower than those using new formula based on new specification.Therefore it is suggested that the old city should improve its drainage system by increasing pipe diameter, optimizing the pipe network and so on.