Resistance studies of overbank flow in rivers with sediment using the flood channel facility

Some large scale experiments concerning equilibrium sand channels with overbank flow are described. The experiments were undertaken in the UK Flood Channel Facility (FCF) configured into a straight compound channel with fixed banks, a mobile main channel composed of uniform sand with a d50 of around 0.8mm, and two symmetric floodplains. The main channel alluvial resistance changed with flow depth and discharge in a complex way arising from the effects of both bedforms and the floodplain/main channel interaction processes. Overall, zonal and local resistance coefficients for this type of channel are reviewed and the data discussed in relation to practical modelling of alluvial channels with overbank flow.