藏东南多依弄巴流域冰湖溃决危险性评价

Hazard assessment of glacial lake outbursts in the Doyinongba Basin,southeastern Tibetan Plateau

冰湖溃决灾害是指冰湖坝体突然破坏引发溃决洪水或溃决泥石流的现象,对下游人类活动和自然环境造成严重影响。近年来,藏东南地区冰川快速退缩,冰湖数量和规模显著增加,冰湖溃决事件广泛发生。基于1995-2021年多时相Landsat系列遥感影像、Sentinel-2A遥感影像,结合RAMMS水文动力学模型方法,对藏东南地区多依弄巴流域内冰湖、冰川进行动态变化分析,模拟冰崩危险体触发冰湖溃决和冰湖溃决泥石流的演进过程,根据泥石流模拟中的流速和流深对冰湖溃决可能影响的区域进行危险性分区。结果表明:流域内冰川面积由1995年的14.05 km^(2)退缩为2021年的9.43 km^(2),年均退缩率约为0.15 km^(2)/a。流域内共发育3处冰崩危险体,均可能触发冰湖溃决。潜在危险冰湖在全溃情况下,溃决泥石流会冲出沟口堵塞然乌湖湖口和帕隆藏布主河道,对下游居民和道路造成影响,影响范围约4.05 km^(2),其中高危险性区域约2.55 km^(2)。危险性评价结果可为多依弄巴流域未来土地利用规划和防灾减灾提供依据,也能为藏东南地区冰湖溃决型泥石流危险评估提供参考。

Glacial lake outburst disasters are the phenomena of outburst floods or debris flows induced by the sudden destruction of glacial lake dams.It has a serious impact on human activities and the natural environment.Recently,the glaciers in the southeastern Tibetan Plateau have retreated rapidly,and the number and scale of glacial lakes have increased significantly,causing frequent occurrences of glacial lake outburst in the southeastern Tibetan Plateau.Dynamic changes in glaciers and glacial lakes,process simulation of the glacial lake outbursts triggered by ice avalanches,and the movement process of glacial lake outburst debris flows were investigated by combining multitemporal Landsat series satellite images,Sentinel-2A satellite images from 1995 to 2021,and the rapid mass movement simulation hydrodynamic modeling(RAMMS).Hazard zoning of debris flow areas was estimated according to the flow velocity and flow depth in the debris flow simulation.The results indicate that the glacial area in the basin shrinks from 14.05 km^(2)in 1995 to 9.43 km^(2)in 2021,and the average annual rate of shrinkage is 0.15 km^(2)/a.There are three ice avalanches in the basin,all of which may trigger the collapse of the glacial lake.When the potentially dangerous glacial lake is drained completely,the debris flow rushing out of the ditch may block the mouth of Ranwu Lake and the main river channel of Palongzangbo,posing a threat to the residents and roads downstream.The impact area is approximately 4.05 km^(2),and the high-risk area is approximately 2.55 km^(2).The above-mentioned results provide a basis for land use planning,disaster prevention,and mitigation inthe Doyinongba basin,guiding the hazard assessments of glacial lake outburst debris flows in the southeastern Tibetan Plateau.