Formation Conditions and Risk Evaluation of Glacial Debris Flow Disasters along International KARAKORUM Highway (KKH)

Abstract

The area of International Karakorum Highway (KKH), a mountain highway connecting northern Pakistan with northwestward China, is an area with dense and frequent glacial debris flow disasters due to the special glacial geology and landform. In this area the three basic conditions inducing glacial debris flow have developed,namely the widely distributed glacial till and ice-snow colluvium, which arise from collapse and landslide, provide the main solid sources of glacial debris flow; the very high and steep slopes, take the landform of steps with a very big gradient, to provide the moving way for glacial debris flow; and the ice-snow melt water from high-mountain, the melt water of glacier avalanche and glacial lake out- burst flood provide glacial debris flow for the force to move. The valley-type debris flow is the main type of glacial debris flow occurred in the area, and it can be classified into further three sub-types according to the water source, namely glacierablation type debris flow, glacier-avalanche type debris flow and glacial-lake- outburstood type debris flow. Based on in situ investigation and analysis of seven controlling variables of glacial debris flow, such as occurrence frequency, catchment areas, volumes of alluvial fan, estimated out flow of every time,vegetation coverage, slope and altitude,to evaluate the risk degree of 8 chosen representative glacier debris flows along KKH. The comprehensive fuzzy evaluation method is applied to evaluate the risk degree of glacier debris flow and then
the evaluation result shows a good correspond with the practical situation, i.e. this method has a valuable application foreground.