Abstract:

[Objective] Significant recent scouring of the riverbed has been observed near Biandanzhou on the right bank of the Taiziji Reach, potentially threatening dike safety, influencing river regime control nodes, and altering the flow distribution ratio of downstream branches. Meanwhile, the navigation conditions in the main channel of Donggang on the right branch remain unstable. [Methods] To ensure flood control and navigation safety, this study analyzed the recent riverbed evolution of the Taiziji Reach based on the latest original underwater topographic observation data and long-term measured records. The study also predicted river regime development trends and proposed corresponding preventive and control measures to address existing issues. [Results] The shoreline has remained generally stable over the years. Except for the straight reach from Changhekou to Xingfucun, the thalweg has shown limited variation. The most significant platform migration, with a maximum lateral migration of approximately 1.1 km, was recorded in the Biandanzhou-Xingfucun area. The thalweg elevation generally exhibited a lower upstream and higher downstream pattern, with alternating changes in elevation over time. The -5,-10, and -15 m contour lines showed a slight overall scouring trend in the deep channel. The Tietongzhou branch would continue to exhibit a pattern of left branch and right main channel, with the right branch showing a general scouring trend. Locally, severe scouring near Biandanzhou was evident inter-annually, with the right bank retreating by approximately 700 m between 1981 and 2021 and the maximum local depth of scouring in the riverbed about 12 m. [Conclusions] It is recommended to implement protective measures as soon as possible for the severely scoured sections near Biandanzhou. Continuous enhancement of hydrological and topographic monitoring and follow-up analyses is essential. Once issues are identified, engineering interventions such as river regulation works should be promptly adopted. The results of this study provide critical technical support for future river management strategies in the Taiziji Reach under new flow-sediment conditions.

Key words: riverbed evolution, thalweg line, river regime changes, bankline change, protection measures, Taiziji Reach