Improvement And Application Of Storm Rainfall Separation Method SDOIF In Estimation Of PMP

Probable Maximum Precipitation(PMP)is the main reference standard for flood control planning of important water conservancy projects,and it is also an important basis for large-scale coastal cities to formulate flood control plans.At present,the Probable Maximum Precipitation may be widely used in various engineering practices.Since the 1930s,domestic and foreign researchers have conducted a lot of research on Probable Maximum Precipitation,and many outstanding research results have emerged.Firstly,this paper will describe the purpose and significance of PMP estimation,and then summarize the current research progress of PMP estimation at home and abroad.Afterwards,the principles and superiority of the six PMP estimation methods commonly used in the world will be introduced respectively.And compare their advantages and disadvantages.Storm transposition mehtod is generally used to estimate the PMP in mountain areas and the difficulty in it is the division of rainstorm.Step-Duration-Orographic-Intensification-Factor Method(SDOIF)is an effective method to segment rainstorms.Therefore,this paper focuses on the variation of SDOIF estimation with the different categories of extreme rainfall,and the relationship between the selection of reference stations and the uncertainty of SDOIF was analysed.Final,the improved SDOIF was applied to PMP estimation in Hong Kong.The 24-hour annual maximum series and the quantiles of 100-year,200-year,and 500-year return period were used to estimates the Orographic-Intensification-Factors(OIF)in Taiwan and Hong Kong.It was found that in the same area,the OIF calculated by annual maximum series and the quantiles of 100-year return period are similar in spatial distribution,but the OIF obtained by quantiles of 100-year return period was more in line with the local topography.Based on a comprehensive consideration of Hong Kong's climate background and topography,the improved storm transposition method is used to estimate the PMP of 24 hours in Hong Kong.Comparing and analyzing the PMP estimation in Hong Kong with the different categories of extreme rainfall,the result shows that if the quantiles of 100-year return period was used to estimate the OIF in Taiwan and Hong Kong during the process of storm transpositon,the resulting average PMP estimation in Hong Kong can reflect the characteristics of the storm center Taihuo Mountain.