A preliminary study on relationship between precipitation and flood disaster in summer in southern China

Abstract:

Based on daily precipitation data of 1181 weather stations and records of flood disaster losses in summer from 1983 to 2011 in southern China, the spatiotemporal variations of precipitation and flood disaster were analyzed and relationship between different rainfall grades and losses was established. According to cluster analysis of precipitation, the southern China is divided into six study regions: (Ⅰ) middle and lower reaches of Yangtze River; (Ⅱ) area between Yangtze River and Yellow River; (Ⅲ) Huanan; (Ⅳ) western Jiangnan; (Ⅴ) upper reaches of Yangtze River; (Ⅵ)southwest China. Station-days(SD) of rainfall grades over the southern China exhibits a distinct three-peak distribution with peaks at 0~5mm, 50~60mm and 100~130mm. The SD of large rainfall grades (>50mm) in 1990s is significantly higher inⅠand Ⅳ. The distributions of rainfall grades are similar inⅡ,Ⅴand Ⅵ, with heavy rain decreased dramatically in 1980s. There are more extreme precipitation events occurred in 1990s and 2000s in Ⅲ. Similar to the distributions of SD of rainfall grades, impact population, impact area, direct economy loss and agricultural economy loss with unimodal distributions inⅠand Ⅳ are more serious in 1990s. In Ⅱ, Ⅴ and Ⅵ, disaster losses are trimodally distributed, with peak values in 1991, 1998, and 2006. The disaster losses exhibited bimodal distribution, reaching peak values in 1994 and 2006 in Ⅲ. In general, four kinds of disaster losses reach the maximum values in Ⅰ in 1990s. Based on the average SD of heavy rain (25~50mm), rainstorm (50~100mm) and heavy rainstorm (100~250mm), the values of different disaster loss indexes could be calculated by twenty established multiple regression equations, with all correlation coefficients larger than 0.4, passing a significance level of 0.001. The increased values of flood disaster losses caused by heavy rainstorm are about one order of magnitude larger than those by heavy rain and rainstorm. The distribution of SD of rainfall grades would reflect the characteristics of flood disaster loss more appropriately than the distributions of rainfall.