Understanding sediment transfer and morphological change for managing upland gravel-bed rivers

Abstract

Upland river systems constantly evolve in response to a wide range of complex and interlinked processes. These include internal factors such as the discharge, sediment supply and transfer, and the role of the channel boundary. All are influenced by external catchment-scale factors including climate and land use. Managing these systems to reduce flood risk, prevent bank erosion and preserve habitats is typically carried out without sufficient consideration of the complex interrelationships governing the fluvial system. This is partly due to a lack of broad-scale thinking and partly due to the intensive field-based data collection required to inform the processes. As such, decisions are often ill-informed, becoming unsuccessful or simply shifting the problems elsewhere in the system. Furthermore, the continually changing nature of rivers makes management more challenging as an implemented scheme is highly unlikely to remain effective in the long term. While upland catchment hydrology and the implications of climate and land-use change have received much attention in recent decades, in-channel interactions between sediment transfer and morphological change have been relatively neglected. These interactions are fundamental to flood risk, lateral channel adjustment, and habitat and ecology; thus, they require a more concentrated research effort. Central to this is a more holistic approach to catchment operations and a greater understanding of the links between the in-channel dynamics and broader catchment changes.