Abstract: Snow avalanche is one of the factors of assessing glacial lake risk,and it is necessary to research the risk assessment of glacial lakes by using snow avalanche models developed by Europe and America for the Himalayas where flood caused by glacial lake outburst occurs frequently. In this paper,based on ICIMOD IKONOS DEM and Landsat-TM data,the factors attributed to avalanche formation,such as the altitude,plan curvature,slope and land cover,were extracted by using the GIS means,and then the PATAs (Potential Avalanche Trigger Areas) in the study area were assessed,according to Av=(Al+Fy)×S×Rg model. In addition,the snow avalanche run-out distance was estimated by using GIS methods and α-β model. According to the estimated results,the "low" values were mainly distributed over the valley floor and slope with dense forest,where the generation probability of potential snow avalanche was very low,while the“high”and“relatively high”values were mainly distributed over the glaciers or hillsides with slope of 30°-50°,full of rock or grass,and probability of generating potential snow avalanche. The results also showed that there were 98 PATAS in the study area,ten of them could spread into the glacial lakes,and the stability risk of these glacial lakes was resulted in. On which potential snow avalanche should be considered as one of the factors inducing the outburst of only 9 glacial lakes in assessing the glacial lake risk in the study area.

Key words: GIS, snow avalanche, avalanche trigger area, glacial lake, risk assessment, Koshi River Basin, Himalayas