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 Af increases at a rate slower than the increase in Ss, 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 Af and Ss is dependent upon bed slope and that the response of Af to an increase in Ss in unconfined braided rivers may be different than that on steep alluvial fans.

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