The hydraulics and morphology of secondary channels within the lower Fraser River gravel reach were examined using data collected with an acoustic Doppler profiler during the large 2002 freshet. Data were collected over an area of channel (subreach), for a range of subreach morphologies (upstream, mid, and downstream). As suggested by visual evidence, at-a-station hydraulic geometry of subreach types stratified along gradients of width, depth, and velocity. Fish habitat is more abundant and more persistently available in the wide, deep downstream subreaches, but higher velocities preferred by some species occur in the mid stream and upstream subreaches. Additional high-flow data, used to develop bank-full scaling relations (classical downstream hydraulic geometry), conformed well to a simple power law up to and including data points from the main channel. However, width and depth exponents deviated from classical results. Investigation suggests that the relations observed in this study approach expected relations for constant slope and channel boundary materials.