CAUSES FOR THE ROCK AVALANCHE ON THE RIGHT BANK OF XINLONGKOU ON THE KUITUN RIVER AND PROBABILITY OF ITS REOCCURRENCE

Rock-avalanches have often occurred in the monsoon season during the months of July and August in the Xinlongkou region on the Kuitun River. However, the latest avalanche took place in January. To explore the causes for the high frequency of occurrences of rock-avalanches in that area, the authors assess different factors such as regional geological conditions, seismic activities, topography, climate and rainfall indexes. Among them, the fragile geological conditions resulted from long historical tectonic movements attributed to seismic activities and favorable climate conditions have triggered rock avalanches in the area. However, frequent thawing and freezing of snow is an extremely critical inducement for the occurrence of avalanches in winter. In the latest episode, the temperature was abnormally high at noon, and it dropped very quickly at night during that specific winter. High temperature allows snow to thaw and penetrate into cracks during daytime, and freeze and consequently expand in volume at night, which in turn triggered the avalanche. Therefore, the thawing and freezing of snow is a very important factor that should be considered in assessment of rock avalanche for some special areas. This paper also assesses the probability of reoccurrence and scale of avalanche events in the region.