ABSTRACT
The flow-sediment regime entering the Lower Yellow River (LYR) has changed significantly since 1986, which led to continuous aggradation and then degradation in river channel downstream. Bankfull channel geometry adjustment in channel evolution of the LYR is most notable in the braided reach. In this study, the reach-scale bankfull area in the braided reach was estimated and analyzed annually during the period from 1986 to 2012 , based on the surveyed post-flood profiles at 28 sedimentation sections, using a method which integrates a geometric mean based on the log-transformation with a weighted average based on the spacing between two consecutive sections. The magnitude of the reachscale bankfull area responds well to the accumulative effect of incoming flow-sediment conditions both in the flood seasons and non-flood seasons. Empirical relationship for the braided reach was developed between the reach-scale bankfull area and the previous four-year average integrated incoming dischargesediment condition using the nonlinear regression. The relationship demonstrates different impact of discharge and incoming sediment coefficient on the bankfull area and relatively high correlation coefficients between them have been obtained.
