Velocity distribution in a large-scale model of a doubly meandering compound river channel

This paper examines the flow conditions in a compound river channel with an environmentally acceptable geometry. It was found that the structure of the flow in channels of this nature is extremely complex and that approaches commonly assumed in its hydraulic analysis do not account for the large interactions between the main channel and floodplains. Additionally, the results indicate that present assumptions used to determine floodwater levels may be inadequate physical descriptions of the processes being modelled. The experimental results were obtained using a 1:5 undistorted scale model of a proposed new channel required for a diversion of the River Blackwater, Hampshire, UK. This model was constructed in the Flood Channel Facility at HR Wallingford. From the analysis of the results it is concluded that the design of more environmentally acceptable channels should be encouraged, but care is needed in ensuring that they meet the required flood defence standards through the development of better channel design procedures.