Using smart rocks to improve understanding of bedload transport in a proglacial forefield

Glacier-fed streams and their downstream ecosystems are influenced by bedload transport. An excess of bedload supply can lead to hazards, whilst an insufficiency can degrade in-stream habitats.  However, the processes by which bedload is mobilised and transported in such environments remain poorly understood, partly because its direct monitoring is challenging. Recent developments in micro-electromechanical systems (MEMS), particularly inertial measurement units (IMUs) for environmental applications, allow this gap to be addressed. Whilst IMU sensors have been primarily used for landslide and rockfall monitoring, their application to fluvial sediment transport is still emerging. Here, we use an innovative approach in which "smart rocks", rocks equipped with triaxial IMUs (accelerometers, gyroscopes, and magnetometers), are deployed in an Alpine proglacial environment. In combination with wireless data transmission, they can be described as “smart” as they can collect data autonomously and transmit it over quite long distances, via Long Range Wide Area Network (LoRaWAN) technology, which allows near real-time communication.

This work presents preliminary results from field tests conducted in autumn 2025 in the proglacial forefield of the Bas Glacier d’Arolla (Swiss Alps) in order to assess their applicability in a realistic alpine environment and to evaluate their potential for capturing bedload transport. Detailed results of a single particle during the flushing of hydropower infrastructure allow quantification of the forces associated with particle entrainment, transport, and resting phases. Central to the method are issues associated with data transmission and particle traceability. However, this preliminary work already demonstrates the potential of smart rocks as a promising tool for improving our understanding of bedload transport in alpine environments, especially for understanding sediment transport processes at the individual particle scale.