The experimental arrangement for examining the hydraulic characteristics of overbank flows in a meandering mobile bed compound channel at the UK Flood Channel Facility (FCF) is described. The FCF was designed to bridge the gap between small and prototype scales and has been used in a series of experiments on straight: compound, skewed and fixed-bed meandering channels. For the present study the sinusoidal meandering main channel had a mobile sand bed, Several overbank flows were measured with smooth or roughened floodplains, Floodplain roughness was provided by surface-penetrating rod elements, It was found that, for floodplain flows with a relative depth >0 . 2, the average flow velocities over the floodplain, in the valley direction, were greater than in the meandering main channel. The principal main channel bedforms were repeating long dunes, There was also evidence of plunging flow over the main channel at the apex of bends.