下荆江尾闾的熊家洲河段自1950年斜槽裁弯形成新生汊道分流,使得下游七弓岭弯道水动力发生调整,进而加剧河道崩岸,影响河势稳定。采用水文资料和地形数据,基于MIKE21软件建立熊家洲弯道上下游河段(监利—螺山)的二维水动力数值模型,设置不同来流量和新汊道尺寸,模拟新汊道条件改变对七弓岭弯道水动力调整的影响。研究表明:汊道展宽至分流明显后,主流水动力轴线沿七弓岭弯道的凸岸偏转;当汊道尺寸较大时,汊道出流近似垂直于七弓岭弯道颈口上游河岸,加剧颈口上游未守护河段的崩岸,这为原型观测所证实。

Chute cutoff in Xiongjiazhou reach in the tail of lower Jingjiang River occurred in 1950 and gave rise to a new cutoff channel, resulting in the adjustment of downstream hydrodynamic condition in the Qigongling Bend, which further aggravated bank collapse and weakened channel stability. Based on hydrological data and channel topography, a two-dimensional hydrodynamic model of the Xiongjiazhou reach (Jianli-Luoshan) was constructed using MIKE21 to simulate the influence of the cutoff channel development on the hydrodynamic adjustment under different discharges and branch sizes. Results manifested that widening the branch leads to the increasing of flow diversion, and the flow dynamic axis deflected along the concave bank of Qigongling Bend. Given that the branch size enlarged, the outflow of the diversion flow was roughly perpendicular to the upstream bank at the neck of Qigongling Bend, which aggravated bank collapse of the unprotected river bank on the upstream side. The result was confirmed by in situ field observation.