The development of structure in coarse-grained river bed sediments: the key to predicting near-bed flow hydraulics and sediment flux

Funded by

Natural Environment Research Council (NERC)

Period of grant

Three years (January 2011 – December 2013)

Award personnel

Dr Mark Powell (project leader) and Dr Nick Tate (Department of Geography, University of Leicester)
Dr Stephen Rice and Prof Ian Reid (Department of Geography, Loughborough University)
Dr Jo Wood (Department of Information Science, City University).

Introduction and objectives

The project aims to understand the development of bed-surface structuring in gravel-bed rivers and the implications for near-bed flows and bed load flux. A series of flume experiments will be conducted to quantify the inter-relationships between bed-surface grain size and structure, near-bed flow regime, initial motion conditions and sediment transport rate under contrasting flow and sediment supply regimes. The evolution of the bed during the experiments will be characterised using metrics of the surface microtopography and grain size. These will be extracted from high-resolution elevation data collected using a bespoke laser scanning system. Detailed measurements of near-bed flow will be obtained by particle image velocimetry (PIV) and coupled with estimates of entrainment thresholds and sediment transport. The research programme, with its emphasis on quantifying the changing structural properties of gravel surfaces and their influence on flow and sediment transport will extend existing knowledge regarding the nature of bed-surface adjustments in gravel-bed rivers which has, hitherto, largely been restricted to considerations of grain size and qualitative descriptions of structural arrangements.  This will improve our ability to predict sediment transport rates in river systems and will benefit hydrologists, engineers, environmentalists and many other groups who live or work on or near rivers.