Sounding out the river: a new system for monitoring bedload mobilisation and transport

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The mobilisation and transport of coarse sediment, referred to as bedload, has a profound impact on the evolution of mountain rivers, the surrounding basins they feed, and the communities that live within their catchments. However, we have few effective methods to routinely monitor bedload transport in near real-time because it is such a high energy and erosive environment under peak flow conditions. Hence, bedload monitoring can be considered a missing component of real-time environmental monitoring.In 'Sounding Out the River' we take advantage of low cost seismic sensor systems that have become available because of the rise of technology such as the Raspberry Pi computer and the ease to which these systems can be telemetered. We will demonstrate this system for monitoring the mobilisation and transport of bedload along the River Feshie in Scotland, which is catchment already monitored for a range of scientific projects. In order to ensure that the system is useful, usable and used we will co-produce the design with a range of stakeholders including SEPA, CEH, Practical Action Nepal and cbec eco-engineering UK Ltd.Beyond this proposal, we will then be able to address a range of environmental challenges, for example: - In Nepal the supply of coarse bedload to the mountain front has resulted in successive channel avulsion events on the Kosi River. This has caused the displacement of vulnerable people and the deposition of gravels across agricultural land has devastated communities. Through near real-time monitoring of bedload transport, we can better understand the dynamics of such systems and have the potential to develop early warning.- When rivers carry bedload, their erosive capacity increases; and when the bedload is deposited the beds become armoured. This poses a clear challenge for managing critical infrastructure.- Forecasting of flood hazard requires knowledge of the shape of the river bed. However, when flood waters mobilise the bedload, the shape of the bed changes which poses a problem for flood modelling. Our near-real time monitoring system has the potential to inform where and when we would expect flood models to start breaking down.- Bedload transport is an important process that cascades in the wake of other hazards, such as the monsoonal mobilisation of coarse sediment derived landslides triggered by the 2015 Nepal earthquake. It is often the case that these secondary processes (bedload transport) do not receive the same attention as the primary hazard (earthquake induced landsliding) because the uncertainty is often described as cascading, implying growing uncertainty. We believe that through the effective use of the monitoring proposed in this project, we have an opportunity to constrain the uncertainty and manage this cascading hazard.