Length scale of braided river morphology

Pool-bar topography in single-channel rivers has a length scale proportional to channel width. In braided rivers confluence-bifurcation units are analogous to pool-bar morphology and, in some cases, develop from initial alternate bars. Consequently, confluence-bifurcation units are expected to have length that scales with the central anabranch width and that constitutes a basic length scale braided channel morphology. This idea was tested using measurements from a physical model of a gravel bed braided river and from aerial photographs of braided rivers. Length (distance from confluence to bifurcation), anabranch width, and confluence angle of confluence-bifurcation units were measured. A simple length scaling is evident across the range of scales; confluence-bifurcation length is 4-5 times the channel width. This scaling is a fundamental element of braided river morphology and suggests that braided patterns are created by processes, and have morphological regularity, similar to pool-bar units of low-sinuosity single-thread rivers.