Glacial Lake Outburst due to Moraine Dam Failure by Seepage and Overtopping with Impact of Climate Change

Abstract

気候変動に起因する氷河湖決壊洪水(GLOF)による洪水災害と土砂災害は南アジアのヒマラヤ地域やその他の氷河地帯においてたびたび発生し、下流において深刻な洪水災害をもたらす脅威となっている。氷河湖の決壊の主な原因は、氷塊の移動が急激な水位上昇や浸透流、氷河サージを引き起こし、それによってモレーンダムが破壊されることである。本報は、モレーンダムの破壊に起因する氷河湖決壊を研究したものである。浸透流と水位上昇による越流がもたらすモレーンダム破壊を一連の実験によって検証し、浸透とモレーンダムの破壊について行った数値解析結果と比較した。また、氷河湖に与える全球気候変化の影響も解析し、観測記録にもとづいて氷河湖決壊洪水流量を予測する経験的関係を導いた。

Due to impact of climate change flood and sediment disasters caused by Glacial Lake Outburst Flood (GLOF) are frequently occurred in the Himalaya of South Asia or glacier regions of the world. GLOF poses a serious threat of flood disasters at downstream valley. Outburst of glacial lakes typically occurs due to moraine dam failure caused by glacier mass movement leading to a rapid rise of water level, seepage flow and a surge. The outburst of glacial lake due to moraine dam failure has been investigated. The moraine dam failure by seepage flow and overtopping due to water level rising has been investigated though a series of flume experiments. Numerical analysis of seepage and moraine dam failure has been also performed. The simulated results are compared with the experimental results. The impact of global climate change on glacial lakes is also analyzed. The empirical relationship to predict GLOF discharge has been also developed based on the recorded GLOFs discharge.