Study On Rainstorm Standard Syntaxis Relationship Of Urban Drainage Between Municipal And Water Conservancy In Central Area Of Guangzhou

With the global climate change and the acceleration of urbanization process,urban rainstorm floods occur frequently in recent years and bring huge economic losses to the city.Urban flood control system usually consist of municipal drainage and water conservancy drainage.Therefore,a proper rainstorm standard syntaxis between them is the prerequisite of effective control to urban flood.Central area of Guangzhou is taken as the research object.Based on the analysis of urban waterlogging causes and the syntaxis mechanism of two-stage drainage standard,and considering the difference of sampling method and design duration,this paper studies the standard syntaxis between drainage of municipal and water conservancy from the perspective of rainstorm convergence and constructs the risk analysis model which reflects its syntaxis relation by Copula function.The essence of syntaxis between municipal drainage and waterlogging drainage is revealed first.It discussed on the disaster mitigation mode and disaster mechanism of urban waterlogging,analysed the relationship between drainage of municipal and water conservancy,revealed the syntaxis mechanism of drainage standards between municipal and water conservancy,and suggested that two-level drainage standard syntaxis should be promoted with the law of the corresponding short and long rainstorm.Then study on the influence of different sampling methods on design rainstorm.The variation of the rainfall sequence in Guangzhou was carried out and the results showed a significant increase in the maximal 5 min and 10 min sequences and a significant mutation at 1987.Based on the rainfall data from 1980 to 2013 in Guangzhou,the annual maximum value method and the annual sampling method were used to sample and frequency curve fitting.By analyzing the influence of the two sampling methods on the design of the rainstorm,it is considered that the annual maximum value method will cause the design value of the smaller part of the reproduction period to be too small,and the annual sample is more suitable for municipal drainage.Study on the experience syntaxis of rainstorm standard between two-stage drainage.Mainly to municipal rainstorm and water conservancy rainstorm respectively,it carried on the empirical research on the rainstorm of storm between municipal drainage and water conservancy drainage,and obtained the syntaxis relationship between rainstorm standard of two-stage drainage.For example,giving priority to 30 min once-in-2-year municipal drainage rainstorm,the corresponding 24 h water conservancy drainage rainstorm is once-in-90-years.And giving priority to 24 h once-in-20-year water conservancy drainage rainstorm,the corresponding 30 min municipal drainage rainstorm is once-in-50-years.Study on the syntaxis of rainstorm standard between two-stage drainagebased on certain risk.Through the joint distribution function,the risk analysis model which reflects the syntaxis relationship between rainstorm design standards of municipal and water conservancy is constructed.The combined risk rate of two kinds of long and short storms is calculated,and the syntaxis relation based on certain risk rate is obtained.When municipal drainage period is of 2 to 5 years and water conservancy drainage period is of 20 years,the two types of risk are at 0.75%~1.13% and 16.95%~9.24%,respectively.In practice,subject to objective conditions,it is difficult to increase standard of municipal drainage.Therefore,it is required to build major drainage system.