Abstract:

 This paper analyzed the data of continuous rain from 1971 to 2010 in Longnan， and the conclusions were as follows：continuous rain mainly occurred between May and October， but the highest occurrence frequencies of continuous rain were during the summer harvest and sowing period from May to July and the autumn harvest and sowing period from September to October， which were the most harmful disaster and caused the most serious damage on agriculture in mountain areas in Longnan Combined with data about population， farmland ratio， GDP of Wudu County， etc， by the utilizing ARCGIS software， the maps of the possibility of disasters were gained Then， by overlaying and uniting the background of weather disasters and the vulnerability of disaster bodies， and compartmentalizing the hazard grades， the hazard attributions for continuous rain disasters were achieved From the map， it was concluded that the risk grade of continuous rain disasters was highest in the highaltitude chilly and moist region in Kang County， the south of Liangdang County， Wudu and Wen County， which were the high risk regions The risk grade of continuous rain disasters was lowest in the lowaltitude region in Li County， Tanchang and Cheng County， and in the Bailong River， Baishui River， Xihan River Basin， which were the low risk regions The above research results were significant to plan the flood relief measures reasonable for the upper Yangtze River， to prevent geological hazard and soil erosion， to protect the environment， especially to guide the farmers in Longnan mountainous area to arrange agricultural production strictly and reasonably， which could prevent and relieve damage caused by continuous rain