Risk Division And Assessment Of Typhoon Disasters In Hangzhou City

Natural disaster is one of the most important global problems we are facing, especially typhoon disaster, with its high frequency and intensity, is the most serious one among them. The secondary disasters of typhoon, for example, flash flood, hill landslide, debris flow, etc, are caused by rainstorm, gale and tyhoon precipitation during typhoon happening. These disasters often cause afflicted farmland, damage of houses and casualties, and seriously restrict the social economic development and the protection of resources and environment.Hangzhou is located the northeast of Zhejiang's coast, and is the important area influenced by our country typhoon disaster. According to the statistics of Hangzhou's history typhoon from 1951 to 2009, there are 88 times of typhoon that affected the city of Hangzhou, and 1.5 times of annual average. Among these typhoons, there are 20 times, which caused the severe losses of the social and economic development of Hangzhou, directly through the city. The interaction between urbanization and the density of population make the city to be more vulnerability and to face more threat to Hangzhou. That puts forward some new requirements in the disaster reduction planning and disaster prevention decision. The typhoon disaster that takes place continuously shows that completely accurate forecast and to prevent the occurrence of typhoon disaster are unrealistic. However if we use some effective management strategies, we can avoid or reduce the great loss caused by typhoon.Based on the hazard-formative theory of the formation, development and spread of typhoon disaster, this article selects some appropriate evaluation index of disaster risk. And the map of Hangzhou's typhoon disaster risk division was draw using 100 m X 100 m raster as basic assessment unit, by means of GIS spatial analysis technique for rasterizing evaluation indices and fuzzy comprehensive assessment methods. Five risk zones of Hangzhou, higher risk, sub-high risk, medium risk, inferior risk and lower risk, were mapped. Results show that the typhoon disaster risk in Hangzhou from southwest to northeast had an increasing tendency. The coastal plain, Xiaoshan district, Yuhang city, main urban area of Hangzhou, and so on, is relative high risk, while in the mid-west mountain and hilly area, Jiande city, chunan county, and so on, it is slightly lower. Finally, according to the typhoon disaster situation data in recent ten years, the results are well consistent with actual disaster situation in Hangzhou city.Based on the evaluation framework of Hangzhou's typhoon disaster risk, this paper particularly studies the typhoon disaster, social economic data, landslide, ect. Construction of a typhoon disaster database, the paper selected 88 typical typhoons and the four indicators caused by the disasters between 1985 and 2006. The four indicators, the affected area, the death toll, the loss of housing, and the direct economic losses, carry out an assessment of the situation, and are used to operate quantitative evaluation on the typhoon disaster and space damage status using the gray association model and the information diffusion theory. At the aspect of vulnerability analysis of hazard bearing bodies, the study employs space process in the aspect of the population and economic vulnerability index, the processing makes the space refinement and makes it effective superposition with other risk assessment indexes. Using the sampling information of the 1907 points of geological disasters from 1968 to 2009 in Hangzhou, it is use the evidence weight method to analysis on the probability of the geological disasters in the research area, and then based on this, the paper assessments the landslide risk and realizes the potential landslide forecast and risk divisions.