藏东南冰湖溃决泥石流灾害及其发展趋势

Hazards of Debris Flow due to Glacier-Lake Outburst in Southeastern Tibet

冰湖溃决泥石流是高山冰湖溃决洪水引起的突发性泥石流，是一种自然灾害现象．西藏冰湖溃决泥石流集中分布于东南部的雅鲁藏布江、波曲及朋曲流域等．冰湖溃决泥石流常形成灾害链对藏东南社会、经济危害严重．分析了气温和降水对冰湖溃决和及其所形成的泥石流的影响，认为冰湖的溃决大部分是由于异常气候条件造成的，冷湿的气候有利于冰川的积累，当气候转为湿热和干热或气温突然升高0．6～1．2℃时最易引起冰湖溃决泥石流．通过对西藏地区气候变化的研究，对未来50a藏东南冰湖溃决泥石流的发展趋势作了预测探讨．一般来讲，气温升高，冰川融水的增加有个临界点，当过了临界点后其冰川融水将会减少，冰湖溃决可能性减少，冰湖溃决泥石流也将减少．也就是说，未来西藏东南部冰湖溃决泥石流的发展趋势，将呈倒“U”字型．冰湖溃决泥石流的发生更多地依赖于突发性的降雨增多．

Debris flows due to glacier-lake outburst are caused by the flood, which often brings about chains of hazards to the social and economic development. Such debris flows are concentrated in the valleys of Yarlung Zangbo, Pumqu （Arun） and Poiqu （Bhote-Sunkosi） in the southeastern Tibet. In this paper, the influences of temperature and precipitation are analyzed. It is concluded that the outburst of glacier-lake is attributed to abnormality of climatic conditions. The wet and cold conditions are favorable for the accumulation of glacier, and debris flow can take place easily when it gets wet-warm and dry-warm, or air temperature abruptly raises 0.6-1.2℃. Based on the analysis of climate change, the development trend of debris flow is also discussed in terms of the climate change in the future 50 years. The result is that there is a critical point at which the melting water turns from increase to decrease, thus the possibility of lake outburst will decrease and consequently the debris flow will decrease. In conclusion, the tendency of debris flow due to glacier-lake outburst can be described by an inverse-U shaped curve. These debris flows depend more on the outburst of heavy rainfall in the future.