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，一个巨大的岩石冰雪崩源自印度喜马拉雅山北阿坎德邦的山脊，转变为沿着Rishiganga，Dhauliganga，Dhauliganga和Alaknanda Rivers的快速移动和灾难性的碎片流。该流量杀死了数百人，摧毁或损坏了成熟和构建下水电项目，并对通道和更宽的山谷地板景观进行了严重修改，包括陡峭的山谷侧的稳定。一旦洪水消退，事后的快速分析表明，碎片流沉积的沉积物在某些地方厚度超过20 m，并且该流量能够将直径超过20 m的巨石运输。接下来的12个月对于该河流系统来说是一个关键时期，因为这是我们预测新沉积的沉积物将被大量侵蚀和运输，并且我们相信，这项活动的大部分将发生在距雪崩源约50公里的距离内，其中包括四个水力发电设施，以及四个水力发电设施，以及河流和河流的结构和基础结构。洪水留下的沉积物的这种“重新激活”对当地水电运算师的影响有影响，他们需要预测这些高架沉积物负荷，并相应地计划以降低对大坝出口和隧道的阻塞风险，避免降低排放能力，并损坏机械设备。此外，由于清除了这种新的沉积物，并且初始流量削弱的银行变得更加不稳定，或者在新区域启动了底切，因此山谷侧面不稳定的风险很高。我们还预计，沉积物的沉积也可能会带来危险，其中这些沉积物与山谷地板能和运输基础设施相交。为了紧急预测洪水后通道修饰的速率和模式，我们将使用能够模拟河流流量以及沉积物的侵蚀，运输和沉积物的计算机模型。我们将在最初的一年内运行此模型（包括夏季季风，这会增加河流排放的命令级），我们将生成关键的摘要数据集，可以迅速将其传达给国内最终用户。我们已经可以访问我们需要设置和运行模型所需的大多数数据，并且项目合作伙伴的位置良好，以提供我们需要执行初始运行并定期检查模型性能的缺失数据。这项工作将由一个国际团队进行，由极端洪水和数值洪水建模，高山景观的水文学以及社区适应（快速）环境变化的专家进行。该团队包括来自英国，印度，加拿大和美国的研究人员，并具有提供高质量科学以告知现实世界决策的集体记录。后续工作将扩大工作范围，以查看更大的区域的沉积物传输和沉积：卫星图像的分析表明，洪水产生的最初沉积物羽流在〜24小时内传播> 150 km，我们预计每年对洪水沉积物的年度重新激活将对这一极端极端事件产生重大影响。

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