Author(s): Junqiang Xia, Jie Li, Shiyuan Zhang, Tao Li
Linked Author(s): Junqiang Xia
Keywords: Channel adjustment, bankfull channel geometry, bankfull discharge, reach-scale, Lower Yellow River
Abstract: The operation of the Xiaolangdi Reservoir has altered the flow and sediment regime downstream of the dam, and causes a channel re-establishment process in the Lower Yellow River (LYR). Recent significant channel evolution in the LYR has led to longitudinal variability in different geomorphic variables at section-scale. Therefore, it is necessary to describe the variations in these geomorphic variables of the LYR using a reach-averaged method. In this study, an integrated approach is proposed for calculating reach-scale geomorphic variables such as bankfull channel geometry and bankfull discharge. Based on the observed hydrological data and cross-sectional profiles during the period from 1999 to 2015, the processes and characteristics of recent channel adjustments in the LYR are investigated, including: (i) The average annual sediment load entering the LYR is only 0. 88�108 tonnes/a, and the cumulative volume of channel scour is 18. 6�108 m3, with the value of the braided reach accounting for 72%; (ii) Substantial adjustments in channel geometry occur in the LYR, with the channel becoming narrower and deeper. The process of channel widening is prominent in the braided reach, with the bankfull width increasing from 972 m in 1999 to 1275 m in 2015, while there is little variation in the bankfull width in transitional or meandering reach. The reach-scale bankfull discharges in these three reaches increase dramatically from 3229, 2339, 3080 m3/s in 1999 to 7321, 5065, 5494 m3/s in 2015, respectively; and (iii) the reach-scale bankfull channel dimensions and bankfull discharge in each reach are closely related to the previous 4-year average fluvial erosion intensity, with the power functions between them being developed in these reaches
Year: 2017