Adjustments in reach-scale bankfull channel geometry and bankfull discharge in the Yellow River Estuary

Sediment load entering the Yellow River Estuary has been greatly reduced and the river bed has been eroded because of the operation of the Xiaolangdi Reservoir,with the occurrence of remarkable channel adjustments. In order to describe comprehensively the bankfull channel geometry and flood discharge capacity in the Yellow River Estuary,a reach-averaged method was used in this study to calculate the reach-scale bankfull channel dimensions and bankfull discharge in the Yellow River Estuary annually from 1990 to 2016. Effects of channel evolution on the reach-scale bankfull channel dimensions and bankfull discharge in the study reach were investigated. In addition,empirical relationships were established between the reach-scale bankfull characteristic parameters and the previous four-year average fluvial erosion intensity during flood seasons in the Yellow River Estuary. These results show that both channel widening and channel incision occurred in the reach after 2003,and the variation in cross-sectional profiles in the Yellow River Estuary was mainly characterized by channel narrowing. Furthermore,bankfull discharge decreased with channel aggradation,and increased with channel degradation. Additionally,the correlation between each bankfull characteristic parameter and fluvial erosion intensity in the Yellow River Estuary was greater than 0.8,indicating the remarkable response of bankfull parameters to the altered flow and sediment regime at Lijin.