Calculation And Analysis Of Short Duration Rainstorm Intensity Formula In Chinese Typical Cities

As the rapid urbanization triggers a number of environmental issues,such as the urban heat island effect,urban flood control and drainage becomes increasingly important.The planning and design of urban outdoor drainage engineering systems always need rainstorm intensity formula for reference,which directly affects the reliability of urban infrastructure.This research focuses on the study of urban short duration rainstorm intensity formula in Chinese cities and its changes under the effect of urbanization.First,using the annual maximum precipitation data of multiple hydrologic stations in Nanjing,the rainstorm intensity formula was compiled.The results indicate that the Pearson-III distribution curve is recommended to fit the frequency adjustment,and the McQuardt method is more accurate for nonlinear fitting of parameters.These methods were used to compile the urban short duration rainstorm intensity formula in this study.Comparing the rainstorm intensity and extreme climate change in urban and suburban areas over different river basins,it is found that the urban and suburban differences of rainstorm intensity and the annual variation of meteorological elements vary under the development of different cities.In Nanjing,which is developed and located over the Yangtze River basin,the rainstorm intensity in the suburbs is larger than that in the urban area.Therefore,the individual rainstorm intensity formulas are needed in the suburban areas of Nanjing.In Hechi,which is developing and located over the Pearl River basin,the rainstorm intensity in the suburb is smaller than that in the urban area,and the difference is insignificant.But the rainstorm intensity of Hechi is increasing with the interdecadal development and the new formulas can be updated accordingly.The analysis of different meteorological elements shows that the urbanization effect results in the increase of temperature and annual maximum daily precipitation,adding more pressure on the urban outdoor drainage systems.The variation of rainstorm intensity was analyzed for six representative cities and the rainstorm intensity formula were derived for every 30-year period,suggesting that the trend of rainstorm intensity varies with different cities.For example,in Beijing,the rainstorm intensity gradually decreased since the 1940 s,but increased significantly since 2010.In Shenzhen,the rainstorm intensity increased since 1963,while began to decrease since 1983.In addition,the long-duration precipitation change is highly associated with the change of short duration rainstorm intensity in each city,which can be considered comprehensively for calculating the rainstorm intensity formula.Based on the spatial distribution of rainstorm intensity changes in the 126 cities across a large region in China,it is found that most cities with an increasing trend of rainstorm intensity are located in the coastal or developed areas,while the increase is more obvious for the longer return period.The increase of rainstorm intensity in Jiangsu and Liaoning provinces is relatively distinct.With the development of cities and climate change,it is necessary to update and compile the regional rainstorm intensity formulas,so as to provide the accurate reference for urban infrastructure construction.