The Establishment And Application Of Rainstorm Intensity Formula In Changshu City

The rainstorm intensity formula is the basement of storm runoff and storm infrastructure calculation in the city.Its correctness is directly related to water infrastructure investment and operation security.Considering the influence of extreme weather,short duration of rainfall intensity has been significantly increased in recent years,the preveious city's storm intensity formula failed to reflect the current status,and the calculation results had large errors.The original formula did not meet the current design requirements and needed to be further revision.In this paper,a case of Changshu City's rainstorm intensity formula calculation and applications are studied.Due to the irregularity of the sample,application of the traditional method of rainstorm intensity variance could not comply with regulatory requirements,resulting in the original formula of rainstorm strength beyond the practical requirements.The traditional method was modified in this study,and the two step optimal method was improved to a step optimal method.The sum of sampling errors and statistics errors was set as the target function,and sampling errors and statistics errors were simultaneously less than errors allows value.The parameters of frequency model and storm strength formulawere optimized,and the results could constrainted within guarantee storm strength formula of sample errors minimum.Afterwards,the storm intensity formula method with several parameters the optimizing calculation method were used to calculate,and the four-parameter standard optimization of rainstorm intensity formula were finally recommended as a new storm intensity formula of Changshu.Both pressure flow of rain water pipes,and maximum rain intensity formula based on the continuity equation,instantaneous rainstorm intensity formula is proposed,and the peak strength of its designed capacity.The current status of drainage design in this state was modified,and the rainwater pipeline design method was improved.Due to the important role of the tube tone storage for cut rain peak flow,gravity flow state condition was more suitable for the strong rainfall than pressure flow state.Hence the reasonable measure during pipeline design was recommended to avoid pipeline in pressure flow condition.For example,reduction of row export river level,application of buried pipeline shallow,and open drains,and flat slope pipeline,way drainage,to improve the waterflow capacity of the rain pipeline.