Characteristics and dynamic analysis of the February 2021 long-runout disaster chain triggered by massive rock and ice avalanche at Chamoli,Indian Himalaya

A massive rock and ice avalanche occurred on the western slope of the Ronti Gad valley in the northern part of Chamoli, Indian Himalaya, on 7 February 7, 2021. The avalanche on the high mountain slope at an elevation of 5600 m above sea level triggered a long runout disaster chain, including rock mass avalanche, debris avalanche, and flood. The disaster chain had a horizontal travel distance of larger than 17,600 m and an elevation difference of 4300 m. In this study, the disaster characteristics and dynamic process were analyzed by multitemporal satellite imagery. The results show that the massive rock and ice avalanche was caused by four large expanding discontinuity planes. The disaster chain was divided into five zones by satellite images and field observation, including source zone, transition zone, dynamic entrainment zone, flow deposition zone, and flood zone. The entrainment effect and melting water were recognized as the main causes of the long-runout distance. Based on the seismic wave records and field videos, the time progress of the disaster was analyzed and the velocity of frontal debris at different stages was calculated. The total analyzed disaster duration was 1247 s, and the frontal debris velocity colliding with the second hydropower station was approximately 23 m/s. This study also carried out the numerical simulation of the disaster by rapid mass movement simulation (RAMMS). The numerical results reproduced the dynamic process of the debris avalanche, and the mechanism of long-runout avalanche was further verified by parametric study. Furthermore, this study discussed the potential causes of disaster and flood and the roles of satellite images and seismic networks in the monitoring and early-warning.     

数字孪生乐安河助力提升小流域防洪决策支撑能力

江西省乐安河流域防汛工作具有小流域防洪的典型特征，针对小流域防洪存在的“四预”体系不完备、决策支持能力不能满足业务需要等问题，开展数字孪生乐安河流域的建设试点。将 WebGIS 引擎和游戏引擎相融合， 结合使用新型水文监测感知体系、BIM + GIS + IoT、多源数据融合等先进技术，搭建视觉真实、数据准确的三维数字孪生场景，构建未来降雨、水文预报、水工程调度、一维/二维演算等多模型耦合的流域防洪智能模拟仿真平台，实现乐安河上游暴雨集中区（婺源）洪水预报全过程的精准化模拟和预报调度一体化，为决策部门提供受灾影响范围这一关键性决策依据研究成果，对构建中小流域（县域）防洪“四预”体系，助力提升小流域（县域）防洪决策支撑能力具有示范性作用。     

韧性城市视角下的甬江流域数字孪生平台建设

针对甬江流域水灾害防御需求,结合韧性城市理论,以防洪减灾“预报、预警、预演、预案”四预体系为导向,利用数字孪生引擎的强大渲染能力,建设全要素的数字孪生流域时空底座,以水文水动力模型、空间计算技术等为重要基础支撑,围绕综合监测、洪涝预报、洪涝预演、综合调度、协同预案等业务需求构建孪生场景,实现了甬江流域数字孪生平台。实践应用表明,该平台成功抵御了甬江流域超标准洪水,并对未来防洪工程体系优化具有启示意义,对其他流域防洪减灾、城市内涝治理工作具有一定的借鉴意义。