PROMOTING IMPACT OF EXTREME DRY-WET CYCLE IN 2010 ON THE LARGE-SCALE DEBRIS FLOWS AND LANDSLIDES IN SOUTHWEST MOUNTAIN AREAS OF CHINA

The year of 2010 is the extreme weather year when El Nio transferred into La Nia, and in this year most geological disasters happened extremely frequently in China. Statistics showed that the hazards concentrated in the southwest mountain areas of China, and the main hazards were the debris flows and landslides(including collapses).Drought happened in early 2010 and rainstorm occurred in rainy season, and the study about single case indicated that it was affected by the natural condition, the dominant factor of hazard was rarely quantitatively analyzed and indicated. In this paper, we coupled characteristic index of dry-wet cycle and the large-scale hazards in the southwest mountain areas of China and analyzed the influence factor of the disasters. Results indicated that 64 percent of the large-scale disasters in the research areas have a corresponding relationship with the drought in 2010, and the dry-wet cycle is one important factor to cause disasters. The influence of dry-wet cycle mainly reflects as follows: large numbers of cracks occurred with the happening of drought, then the rainfall infiltrated along the cracks which resulted in the decrease of resistance and the increase of both seepage pressure and sliding force.