Fluvial processes in the meandering reach of the lower Wei river during the course of degradation

This paper presents an analysis of the changes of the longitudinal and lateral profiles in the meandering reach of the lower Wei river over the period from October 1973 to October 1976 during the course of degradation. Analysis results indicated that retrogressive erosion and subsequent downstream erosion occurred in the reach due to the lowering in the Tongguan elevation and the inflowing water carrying low sediment concentration. At the end of the degradation, the main channel widths of the majority of sections were increased by 70% to 110%, and the elevation differences between the main channel and the floodplain were decreased slightly by 2% to 45%, which caused a decrease in the water stage under the same discharge, the formation of a channel with relatively wide and shallow cross-sectional profiles, and an increase of 50% to 150% in the geomorphological coefficients. Therefore, the degradation in this reach was mainly characterized by channel widening, not by channel undercutting.