Based on GIS,RS and the landscape analysis software,landscape changes in the middle and lower reaches of Houzhai River in Puding County of Guizhou Province from 1973 to 2004 were analyzed.The results indicated that paddy fields and dry fields held a dominant status.In the change of landscape types,forest land reduced continually,dry fields changed complicatedly,and the mutual transformation among grass land,shrub land and forest land was obvious.The area of bare rock increased remarkably in the slope range between 10° and 35°.Artificially 'returning cultivation land into forests and pastures','reclamation by damaging forests and pastures',and natural ecosystem converse succession existed at the same time.Therefore,the whole landscape was in an unstable state.
Guangdong is a developed province in China, but suffers from frequent typhoon disasters which cause great economic loss. Quantitative regional risk assessment of typhoon disasters is important for disaster prevention and mitigation. According to direct economic loss and typhoon intensity information, we established a typhoon disaster loss rate curve using data from 1954 to 2008. Based on GIS spatial module, the economic vulnerabilities of different intensity typhoons were calculated for 98 counties in Guangdong Province. Different intensity typhoon landing frequencies in Guangdong were also calculated, and used to indicate typhoon disaster probability. A risk assessment model was established to assess economic loss risk under different intensity typhoons in Guangdong. The results show that economic loss risk caused by typhoon is more than 10 thousand million CNY; according to typhoon intensity grade, economic risk is up to 10.467, 14.429, 7.753 and 13.591 thousand million CNY for slight, light, medium and severe typhoons, respectively. The Pearl River Delta is the highest risk region, especially Guangzhou, Dongguan, Shenzhen, Zhongshan and Zhuhai. Risk value decreases from Pearl River coastal outfall to the inland in a radial pattern. Inland areas far from coastal counties have lower risk, and the risk value is less than 50 million CNY. When typhoon intensity increases from slight to medium, the risk in western is higher than in eastern parts, but when typhoons become to severe, the risk value in eastern Guangdong part is higher than in the west.
