SUPERSLUG

Deconstructing sediment superslugs as a legacy of extreme flows
Himalayan river with rocks, mountains and people hiking on the bank

SUPERSLUG

Deconstructing sediment superslugs as a legacy of extreme flows
Title: SUPERSLUG: Deconstructing sediment superslugs as a legacy of extreme flows
Funding amount: £1 million
Location: Plymouth, UK; Chamoli, India
Dates: 1 July 2024 – 30 June 2028
Project partners: Newcastle University, University of Exeter, Manchester Metropolitan University, University of Leeds, University of Staffordshire, Indian Institute of Technology Roorkee (India), Wadia Institute of Himalayan Geology (India), Laboratoire d'Etudes en Géophysique et Océanographie Spatiales (France), University of Calgary (Canada)
University of Plymouth PI: Dr Matt Westoby  
University of Plymouth staff: Qiuyang Chen  
 


SUPERSLUG aims to transform how we understand the long-lasting impacts of catastrophic sediment-rich flows in high mountain regions. 
Using drones, smart sensors, satellite data and advanced numerical modelling, the project seeks to uncover how vast 'superslugs' of sediment move through river systems, shaping hazards and potentially impacting infrastructure. 
Focusing on uniquely data-rich landscapes affected by the 2021 Chamoli disaster in the Indian Himalaya, SUPERSLUG will deliver powerful new tools and insights to help communities and decision makers manage these changing landscapes with greater confidence.

Extreme sediment-rich flows leave a lasting landscape imprint that can continue to reshape river systems and their hazards for decades, but understanding these 'landscape legacies' is highly challenging, especially in remote, mountainous landscapes.

Through SUPERSLUG, we will shed light on how vast sediment 'slugs' move through the headwaters of the Ganges, helping hazard practitioners, water resource managers, and local communities to plan, adapt and build resilience in a rapidly changing, and increasing hazardous, climate.

Matt WestobyDr Matt Westoby
Associate Professor of Physical Geography

Objectives

Objective 1
Measure the passage of sediment slugs through flood-affected mountain rivers at the catchment scale by creating and analysing detailed 3D land surface models and other geospatial data derived from drone surveys and satellite imagery.
Objective 2
Measure how sediment moves through disturbed river channels at the local scale using novel sensor suites, including wireless smart tags and passive seismics. These data will push scientific understanding of grain- and reach-scale flood sediment response.
Objective 3
Detect and track fast-moving, fine-grained sediment slugs using cloud-processed, high-resolution satellite imagery and geospatial analysis, shedding light on the long-range transmission of flood impacts.
Objective 4
Use new field and remote sensing data (from Objectives 1–3) to calibrate a large-scale numerical model that allows us to simulate how sediment slugs travel through a Himalayan river system, enabling predictions of sediment fate and potential impact.
Objective 5
Work with academics, practitioners and communities to effect knowledge transfer and turn project insights into practical tools and strategies for managing hazards and improving geohazard resilience.

Context of the issue

SUPERSLUG is grounded in the urgent need to understand what happens after catastrophic sediment-rich flows tear through high mountain landscapes. These extreme events, triggered by landslides, rock ice avalanches and glacial lake outburst floods, can mobilise enormous volumes of sediment, causing immediate destruction and long-term disruption to rivers, infrastructure, ecosystems and communities. 
Their most far-reaching landscape legacy is the formation of fast moving 'superslugs' of sediment that travel downstream for years or decades, altering river channels, increasing flood hazard, damaging hydropower systems, and degrading water quality far from the original disaster source. As climate warming destabilises mountain environments and increases the likelihood of such events, these overlooked legacy impacts pose growing risks, particularly for rapidly developing regions with expanding populations and critical infrastructure.
The project builds from the team's high-profile pilot studies (Shugar et al., 2021; Westoby et al., 2023) that explored the immediate impacts of the 2021 Chamoli disaster in the Indian Himalaya – one of the most data‑rich catastrophic flow events ever recorded. 
That work revealed how quickly vast sediment deposits can be remobilised and how sediment superslugs propagate downstream, potentially threatening major hydropower and water treatment facilities hundreds of kilometres away. 
These insights exposed major gaps in our ability to observe, track and predict superslug behaviour, setting the stage for SUPERSLUG's integrated approach. 

How the project addresses the issue

SUPERSLUG directly addresses the critical gaps in understanding the long-term impacts of extreme sediment-rich flows by building and proving a comprehensive framework for observing, tracking and modelling sediment superslugs as they move through mountain rivers. 
By combining cutting-edge field monitoring, satellite remote sensing and advanced numerical modelling, the project overcomes long-standing observational barriers and transforms scientific insight into practical tools. This integrated approach equips decision makers with the evidence they need to anticipate, mitigate and adapt to these far-reaching hazards, strengthening resilience for communities and infrastructure downstream.
The confluence of the Alaknanda and Bhagirathi Rivers, which represents the source of the Ganges. Differences in the colour of the water are the result of variations in sediment load, which can be caused by landscape disturbances originating higher in the catchment. Matt Westoby
 
 
 

Funded by

Centre for Research in Natural Hazards and Risk Reduction (CHaRR)

Natural hazards cause billions of dollars of damage, significantly effect people's lives, and can have long-term negative environmental effects. Climate change, population growth and urbanisation exacerbate events, and increasingly devastating cascading and multihazard sequences result in unexpected chains of events. 
CHaRR brings together researchers from across the University to tackle outstanding questions in hazard science, risk and reduction, thus contributing to the targets of the Sendai Framework for Disaster Risk Reduction 2015–2030 as well as the UN Sustainable Development Goals.
 
Lava stream flowing into the sea