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 wi th an environmentally acceptable geometry. It was found that the struc ture of the flow in channels of this nature is extremely complex and t hat approaches commonly assumed in its hydraulic analysis do not accou nt 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 wa s constructed in the Flood Channel Facility at HR Wallingford. From th e analysis of the results it is concluded that the design of more envi ronmentally acceptable channels should be encouraged, but care is need ed in ensuring that they meet the required flood defence standards thr ough the development of better channel design procedures.