黑河下游河岸侵蚀触发颈口裁弯的数值模拟概化研究

Conceputually Numerical Simulation of Neck Cutoff Triggered by Bank Erosion in the Lower Black River

为复演黄河源黑河下游河岸侵蚀触发颈口裁弯的极端地貌过程,基于2018年7月实测洪峰流量过程,采用断面尺度的崩岸模型(BSTEM),以1d为时间尺度概化模拟在3种不同侵蚀方式(上游单侧、下游单侧和上下游两侧共同作用)下的颈口缩窄过程与裁弯时间.采用上下游两侧共同作用的河岸侵蚀模拟的结果表明,颈口贯通的时间为2018年7月15日,这与崩岸贯穿颈口的实际时间是一致的.颈口双侧崩岸比上游或下游单侧崩岸触发颈口裁弯的时间分别提前2d或6d.可知,极端洪水作用下的加速河岸侵蚀是黑河下游弯道提前发生颈口裁弯的直接触发原因.

Based on the measured data of flood peak discharge in July 2018,the section⁃scale bank collapse model(BSTEM)was used to simulate the neck cutoff process and cutoff time under the three different erosion modes(upstream,downstream,combined upstream and downstream)for reproducing the neck cutoff event triggered by bank erosion in the lower reaches of the Black River of the Yellow River Source.The results of the combined upstream and downstream erosion mode show that the time of the flow intersection at the neck is on July 152018,which is consistent with the time of the actual bank collapse triggering the neck cutoff.The cutoff time of the combined erosion mode is 2 days or 6 days earlier than that of the upstream or downstream bank erosion mode,respectively.The accelerated bank erosion caused by this extreme flood event is the direct driving force of neck cutoffs occurred in advance in the lower Black River.