RESPONSE OF MAIN CHANNEL MORPHOLOGY IN WANDERING SECTION DUE TO THE INFLUENCES OF RUNOFF SEDIMENT AND BOUNDARY CONDITIONS OF REGULATION ENGINEERING IN LOWER YELLOW RIVER

Since the Xiaolangdi reservoir was put into operation, the runoff and sediment conditions entering the lower reaches of the Yellow River have changed greatly. In addition, with the gradual improvement of river regulation projects, the river channel shape of the wandering reach has changed significantly. Based on the measured large section data from 1999 to 2019 after flood season, the shape parameters of bankfull channel are analyzed. Based on the geometric average of logarithmic transformation and the weighted average method of section spacing, the bankfull shape of wandering channel is analyzed. The results show that the main channel shape of Tiexie section is mainly scouring downcut from 1999 to 2005, and the fluvial facies coefficient is stable at 7 after 2005. The widening and scouring of the main channel coexist in the section of the Huayuankou from 1999 to 2005, and the scouring downcutting is the main one after 2005, and the fluvial facies coefficient is stable at 20 after 2015. The main channel of Jiahetan section was widened and the bankfull river depth decreased from 1999 to 2003. The main channel widening and scouring coexisted from 2003 to 2012, and scouring and cutting were the main ones after 2012. The main channel of Gaocun section coexists with widening and scouring from 1999 to 2005, and mainly undergoes scouring and cutting after 2005. The shape of main channel in wandering section coexists with widening and scouring from 1999 to 2013. After 2013, scouring and cutting are dominant, and the shape of main channel in wandering section develops towards narrow and deep direction. The empirical function relation between the form of bankfull channel and the runoff and incoming sediment coefficient and project density in flood season and non-flood season is established. It is shown that the influence degree of runoff, incoming sediment coefficient and project density on the form parameters of bankfull channel is different.