Relationship between sediment supply and avulsion frequency in braided rivers

Abstract

The interplay between sediment supply (Ss), sedimentation rate (Sr), and the frequency of channel avulsion (Af) exerts a primary control on alluvial architecture. In order to investigate the effect of sediment supply on avulsion frequency, four Froude-scale model experiments of an aggrading braided river were undertaken in which the magnitude of Ss was progressively increased over an eightfold range. The value of A_f increases at a rate slower than the increase in S_s, contrary to the trend previously reported by Bryant, Falk, and Paola in their experimental study on alluvial-fan dynamics. These results suggest that the relationship between A_f and S_s is dependent upon bed slope and that the response of A_f to an increase in S_s in unconfined braided rivers may be different than that on steep alluvial fans.