Rainstorm Waterlogging Risk Assessment Based On RS&GIS

In this paper, the composition and structure of the rainstorm waterlogging system are analyzed based on the theory of natural disaster system, the risk of rainstorm waterlogging is resulted by disaster-causing factor and disaster-bearing factor. This paper takes the middle and lower reaches of Hanjiang River Basin as the research region, the hazard of disaster-causing factor, vulnerability of disaster-bearing factor and risk of rainstorm waterlogging are analyzed by RS and GIS.(1) Rainstorm waterlogging system is the synthesis of nature and the social factor, which can be divided into pregnant disaster environment, disaster-causing factor, disaster-bearing factor and disaster-regulating factor. There is no absolute boundary among the factors, and they are a close link as a whole.(2) There are two different concepts between the risk and condition of rainstorm waterlogging. The risk emphasizes natural property of rainstorm waterlogging, i.e. the probability, intensity and distribution of rainstorm waterlogging are occurred in the region without the consideration of human interference; however, before and after disaster, if people take some physical or social measures to reduce the loss based on the understanding of disasters, it’s the so-called condition of disaster.(3) The direct disaster-causing factor is precipitation, and the indirect ones are runoff, river density, elevation and slope, the indirect disaster-causing factors belong to the category of the pregnant disaster environment in the broad sense. The correlational analysis method is applied to analyze the correlation between the disaster-causing factors. The slope and relief amplitude are high correlation, in order to reduce the redundancy of data and make the calculation simple, the relief amplitude is removed in this paper.(4) The explicit expression of disaster-causing factor hazard is implemented through the principal component analysis. The results show that the hazard degree of grade V and IV areas are mainly distributed in the lower reaches of Hanjiang River Basin, the grade V and IV areas are mainly distributed in the middle reaches of Hanjiang River Basin. The hazard of disaster-causing factor generally decreases from southeast to northwest.(5) The risk of rainstorm waterlogging has significant differences in space, the risk of rainstorm waterlogging shows geometric progression distribution in different region, and it’s order of grade has consistency with population and economy’s in the spacial distribution. Wuhan city and Qianjiang city are in the region of grade Ⅴ, the level of risk is much higher than the other regions. Grade Ⅳ and Ⅲ areas are distributed in almost every city. The level of risk is lower in Baokang City, and Shennongjia forest region is in grade Ⅰ.