Geomorphic adjustments of channel bars in the braided reach of the lower Yellow river from 1986 to 2018

Abstract

Channel bars are an important aspect of braided river morphology, and have a significant effect on flood control, waterway navigation and the aquatic ecological environment. In this study, the number, area and shape index of channel bars in the braided reach of the Lower Yellow River (LYR) were determined based on remote sensing images from 1986 to 2018, and the evolution characteristics of channel bars were investigated temporally and spatially. The effects of flow regime, sediment supply and bank erosion were also investigated as part of geomorphic adjustments of channel bars in the braided reach. The findings of this study indicate that the number and area ratio of channel bars were lower in the pre-dam period when water levels were higher and higher in the post-dam period when water levels were lower. More variance in the peak discharge may lead to more variance in channel bars indices in the braided reach. The number of channel bars per unit width is closely related to the specific stream power in the braided reach, and a larger specific stream power leads to more channel bars. The total area of channel bars increased with an increase in the reach-scale bankfull width, which indicates that bank erosion was closely associated with the adjustments of channel bars in the braided reach of the LYR.