The Role of Sediment Transport and Sediment Supply in the Evolution of River Channel and Floodplain Complexit

River channel and floodplain complexity, including the diversity of river bends, pool depths, oxbow lakes, scroll bars, and related features, is generated by the tendency of river channels to migrate laterally. The primary driver of this migration is the flow field, which molds the sediment of the channel boundary and is in turn altered by the gradient, curvature, and bar forms of the channel. However, the rate and texture of the sediment supply, determined by the topography, lithology, climate, and vegetation cover of the drainage basin, play important roles in affecting the resultant rates of bank erosion, bend growth, and form of floodplain erosion that generate sinuosity and oxbow lake production. We illustrate this point with examples of our recent studies of channel mobility and floodplain erosion and sedimentation. The supply of bed material to a reach accelerates point bar growth that increases the cross-channel acceleration of flow and intensifies bank erosion. The vulnerability of floodplain surfaces to chute incision, which depends on point bar growth, floodplain texture, floodplain gradient, and vegetation cover, limits channel sinuosity and alters the average rate and length of oxbow lakes. The form and rate of sedimentation in oxbow lakes and thus the length of time they survive as open water bodies before filling depends on the initial diversion angle of the cutoff (and therefore, on average, the sinuosity of the channel), and the relative supplies of bed material and wash load