This paper presents an analysis of the changes of the longitudinal and lateral profiles in the meander- ing 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 con- centrations.At the end of the degradation,the main channel widths of the majority of sections were increased by 70 to 110 percent,and the elevation differences between the main channel and the floodplain were de- creased slightly by 2 to 45 percent,which caused a decrease in the water stage under the same discharge,the formation of a channd with relatively wide and shallow cross-sectional profiles,and an increase of 50 to 150 percent in the geomorphological coefficients.Therefore,the degradation in this reach was mainly characterized by channel widening,not by channel undercutting. This paper presents an analysis of the changes of the longitudinal and lateral profiles in the meander-ing 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 con- centrations. At the end of the degradation, the main channel widths of the majority of sections were increased by 70 to 110 percent, and the elevation differences between the main channel and the floodplain were de- creased slightly by 2 to 45 percent, which caused a decrease in the water stage under the same discharge, the formation of a channd with relatively wide and shallow cross-sectional profiles, and an increase of 50 to 150 percent in the geomorphological coefficients.Therefore, the degradation in this reach was mainly characterized by channel widening, not by channe l undercutting.