Tracking sediment waves through Himalayan fluvial cascades following extreme mass flows

山地景观经历突发和剧烈的地质灾害，如滑坡，湖泊溃决洪水和泥石流。由于气候变化，预计此类事件的规模和频率将增加，从而增加地貌的不稳定性。这些景观也正在经历快速的人口增长，直接使人员和资产暴露于地质灾害，但也使他们暴露于事件后表现出来的遗留影响，这些影响通常被忽视和无法量化。许多山地地质灾害的遗留影响是增加了河流中粗泥沙的输移。这是一个问题，因为作为“推移质”的沉积物是河道调整的主要驱动力。这些调整影响到：1）洪水危害，通过改变河床高程; 2）河岸基础设施的完整性，例如水电，通过阻塞进水口和快速填充水库，以及3）河流生态，通过重组河道底质。因此，它是至关重要的，以产生良好的约束知识的步伐和方式，推移质输运制度的演变在山区河流后，极端的干扰。然而，由于技术限制和与在不稳定的洪水后景观中工作相关的挑战，我们几乎没有关于这些系统行为的第一手资料，这是该项目旨在解决的问题。这个新项目将巩固来自英国和印度的领先研究人员的新的国际合作伙伴关系。该团队由普利茅斯大学领导，与印度理工学院鲁尔基（IITR）和喜马拉雅地质瓦迪亚研究所（WIHG），埃克塞特大学和纽卡斯尔大学密切合作。多样化的团队带来了地貌学、水文学和环境传感器网络方面的互补专业知识，如果没有国际合作伙伴的区域知识、技术能力和实地经验，这项工作是不可能的。该项目还具有突出的早期和早期到中期的职业生涯研究人员在领导角色。通过合作，我们将应用一套创新的环境监测和建模工具来模拟印度北阿坎德阿拉克南达河的水文和泥沙输运状况，该河流在2021年2月经历了一场极端泥石流，造成200多人死亡，并引发了作为遗留影响的泥沙输运增强，这一点通过试点工作得到了证明。为了实现我们的目标，我们将：1）开发一个新的Alaknanda流域水文模型，使我们能够识别和解开流量的关键组成部分（例如融雪，降雨）。这一信息将用于更好地了解沉积物运移的水文驱动因素; 2）利用无人机和卫星观测和建模，量化河沙的粒度特征。这些信息将使我们能够探索粒度随时间的下游变化，并研究Chamoli事件的影响; 3）部署创新、低成本的“智能”标签，以跟踪卵石和卵石作为推移物的运动。我们将补充这些数据的时间和推移质输运的相对大小，使用低成本的被动地震测量。我们将通过IITR和WIHG的联合实地考察和讨论，以及定期的一系列虚拟项目会议和研讨会，亲自实现技能和知识的传授。我们将在同行评审的开放获取期刊上发表结果，并将编写一份技术摘要报告，分发给当地利益攸关方。项目的成功将导致未来的联合供资投标，这将评估水电作为山区河流粗泥沙运输干扰因素的作用，并探索可以减轻极端洪水的直接和遗留影响的操作方法。在此过程中，我们将进一步巩固涉及区域学者和从业人员的更广泛的研究网络，同时支持两国早期职业研究人员的发展。

Mountain landscapes experience sudden and violent geohazards, such as landslides, lake outburst floods, and debris flows. The size and frequency of such events is anticipated to increase due to climate change, enhancing landscape instability. These landscapes are also experiencing rapid population growth, directly exposing people and assets to geohazards, but also exposing them to legacy impacts which manifest after an event and are commonly overlooked and unquantified. A legacy impact of many mountain geohazards is enhanced coarse sediment transport in rivers. This is a problem because sediment travelling as 'bedload' is the primary driver of river channel adjustment. These adjustments affect: 1) flood hazard, by modifying channel bed elevation; 2) the integrity of riparian infrastructure, e.g. hydropower, by blocking intakes and rapidly filling reservoirs, and 3) fluvial ecology, by reorganising channel substrate. It is therefore vital to generate well-constrained knowledge of the pace and manner in which the bedload transport regime evolves in mountain rivers after extreme disturbances. However, due to technical limitations and challenges associated with working in unstable, post-flood landscapes, we have little first-hand information on the behaviour of such systems, which this project aims to address.This new project will consolidate a new international partnership of leading researchers from the UK and India. The team is led by the University of Plymouth, working in close collaboration with the Indian Institute of Technology Roorkee (IITR) and the Wadia Institute of Himalayan Geology (WIHG), the University of Exeter, and Newcastle University. The diverse team bring complementary expertise in geomorphology, hydrology, and environmental sensor networks, and the work would not be possible without the regional knowledge, technical competencies, and field experience of the international partners. The project also features prominent early- and early-to-mid-career researchers in leading roles. Working together we will apply a suite of innovative environmental monitoring and modelling tools to characterise the hydrological and bedload transport regime of the Alaknanda river, Uttarakhand, India, which experienced an extreme debris flow in February 2021 which killed >200 people and triggered enhanced sediment transport as a legacy impact, evidenced through pilot work.To achieve our aim, we will: 1) Develop a new hydrological model of the Alaknanda catchment, enabling us to identify and disentangle the key components of flow (e.g. snowmelt, rainfall). This information will be used to better understand the hydrological drivers of sediment transport; 2) Quantify the grain size characteristics of channel bars using drone- and satellite-based observations and modelling. This information will allow us to explore downstream transitions in grain size through time and examine the influence of the Chamoli event; 3) Deploy innovative, low-cost 'smart' tags to track the motion of cobbles and boulders travelling as bedload. We will supplement these data with measurements of the timing and relative magnitude of bedload transport using low-cost passive seismics. We will effect skills and knowledge transfer in-person via joint fieldwork and discussions at IITR and WIHG), and a regular series of virtual project meetings and seminars. We will publish results in peer-reviewed open-access journals and will produce a technical summary report which we will disseminate to local stakeholders. Project success will lead to future joint funding bids which will appraise the role of hydropower as a disruptor to coarse sediment transport in mountain rivers and explore operational practices that can mitigate the immediate and legacy impacts of extreme floods. In doing so we will further consolidate a wider research network involving regional academics and practitioners, whilst supporting the development of early career researchers in both countries.