A DEFRA funded project has investigated the infiltration process of fine silt and sand into openwork gravel beds within the Chilworth flume facility. Fine sediments can block the interstitial flow through the spawning beds of salmonid fishes and an increase in the flux of sediment from the land surface to the channel beds is one possible reason that salmonid fish stocks have declined in UK streams and rivers. The laboratory study also developed a novel low-cost tracer to map the general patterns of interstitial flow through the gravel beds and the retention time of fluid within the stream beds.

This project has reported for the first time the detail of flow pattern and sediment transport above antidune bedforms developed in mixtures of fine sand and gravel. Antidunes are bedforms that grow and collapse rapidly making them extremely difficult to study in the laboratory as well as in nature. Using high-speed video and Acoustic Doppler Anometers sufficient data were obtained to describe the flow and sediment transport processes that lead to distinctive sedimentary deposits developed by antidunes in aggradational settings. This information has shown hither-to unforeseen hydrodynamic behaviour and the results will be used to better interpret suspected antidune deposits within the geological record.

People:

Prof. David Sear