Rapid adjustments to catchment sediment yield following a catastrophic rock-ice avalanche and debris flow, Uttarakhand, India

印度北阿坎德邦灾难性岩冰雪崩和泥石流后流域沉积物产量的快速调整

• 批准号: NE/W002930/1
• 负责人: Matthew Westoby
• 金额: $ 4.78万
• 依托单位: Northumbria University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FW002930%2F1
• 关键词: Rapid; adjustments; catchment; sediment; yield

On 7th February 2021 a massive rock-ice avalanche originating from a mountain ridge in Chamoli District, Uttarakhand, Indian Himalaya, transformed into a fast-moving and catastrophic debris flow which travelled along the Rishiganga, Dhauliganga, and Alaknanda rivers. The flow killed hundreds of people, destroyed or damaged mature and under-construction hydropower projects, and caused severe modification to the channel and wider valley floor landscape, including the destabilising of steep valley sides. Once the flood subsided, rapid post-event analysis revealed that sediments deposited by the debris flow were more than 20 m thick in places, and that the flow was capable of transporting boulders exceeding 20 m in diameter. The next 12 months are a crucial period for this river system because this is when we predict that newly deposited sediments will be eroded and transported in vast quantities, and we believe that most of this activity will occur within a distance of around 50 km from the avalanche source, which includes four hydropower facilities and riverside settlements and infrastructure. This 're-activation' of sediments left behind by the flood has implications for local hydropower operators, who need to anticipate these elevated sediment loads and plan accordingly to reduce the risk of blockage to dam outlets and tunnels, avoid reduced discharge capacity, and damage to mechanical equipment. In addition, there is a high risk of further valley flank instability as this new drape of sediment is removed and banks that were undercut by the initial flow become more unstable, or undercutting is initiated in new areas. We also anticipate that sediment deposition could also present a hazard where these deposits intersect with valley floor energy and transport infrastructure.To urgently predict rates and patterns of post-flood channel modification we will use a computer model that is capable of simulating river flow and the erosion, transport, and deposition of sediment. We will run this model for an initial period of one year (including the summer monsoon, which brings an order-of-magnitude increase in river discharge) and we will generate critical summary datasets that can be rapidly communicated to in-country end users. We already have access to most of the data that we require to set up and run the model, and project partners are well-placed to provide missing data that we need to perform initial runs and perform regular checks on model performance. The work will be carried out by an international team comprised of experts in extreme floods and numerical flood modelling, the hydrology of high mountain landscapes, and community adaptation to (rapid) environmental change. The team includes researchers from the UK, India, Canada and the USA with a collective track record of delivering high quality science to inform real-world decision-making. Follow-on work will broaden the scope of the work to look at sediment transport and deposition over a much larger area: analysis of satellite imagery shows that the initial sediment plume generated by the flood travelled >150 km in ~24 h and we anticipate that annual re-activation of flood sediment will have significant impacts on the hazard posed by this extreme event.

2021 年 2 月 7 日，源自印度喜马拉雅山北阿坎德邦查莫利区山脊的大规模岩冰雪崩转变为快速移动的灾难性泥石流，沿着 Rishiganga、Dhauliganga 和 Alaknanda 河移动。洪水造成数百人死亡，摧毁或破坏了成熟和在建的水电项目，并导致河道和更广泛的谷底景观发生严重改变，包括陡峭谷壁的不稳定。洪水消退后，快速的事后分析显示，泥石流在某些地方沉积的沉积物厚度超过20 m，并且泥石流能够输送直径超过20 m的巨石。未来12个月是该河流系统的关键时期，因为我们预测此时新沉积的沉积物将被大量侵蚀和搬运，并且我们相信大部分活动将发生在距离河流约50公里的范围内。雪崩源，其中包括四个水力发电设施以及河边定居点和基础设施。洪水留下的沉积物的“重新激活”对当地水电运营商产生了影响，他们需要预测这些增加的沉积物负荷并相应地制定计划，以减少大坝出口和隧道堵塞的风险，避免排放能力下降和损坏到机械设备。此外，由于新的沉积物被移除，被初始水流底切的河岸变得更加不稳定，或者在新的区域开始底切，因此谷侧进一步不稳定的风险很高。我们还预计，沉积物沉积也可能在这些沉积物与谷底能源和交通基础设施相交的地方造成危险。为了紧急预测洪水后河道改造的速度和模式，我们将使用能够模拟河流流量和河道流量的计算机模型。沉积物的侵蚀、输送和沉积。我们将在最初一年的时间内运行该模型（包括夏季季风，这会导致河流流量增加一个数量级），并且我们将生成可以快速传达给国内最终用户的关键汇总数据集。我们已经可以访问设置和运行模型所需的大部分数据，并且项目合作伙伴可以很好地提供我们执行初始运行和定期检查模型性能所需的缺失数据。这项工作将由一个国际团队执行，该团队由极端洪水和数值洪水建模、高山景观水文学以及社区适应（快速）环境变化方面的专家组成。该团队包括来自英国、印度、加拿大和美国的研究人员，他们在提供高质量的科学知识以指导现实世界的决策方面有着共同的记录。后续工作将扩大工作范围，以研究更大区域内的沉积物输送和沉积：卫星图像分析显示，洪水产生的初始沉积物羽流在约 24 小时内移动了 >150 公里，我们预计每年洪水沉积物的重新激活将对这一极端事件造成的危害产生重大影响。

项目成果

Rapid fluvial remobilization of sediments deposited by the 2021 Chamoli disaster, Indian Himalaya

2021 年印度喜马拉雅山查莫利灾难沉积物的河流快速重新流动

• DOI: 10.1130/g51225.1
• 发表时间: 2023
• 期刊: Geology
• 影响因子: 5.8
• 作者: Westoby M