长江中游典型通江故道物理形态演变特征研究

Morphological evolution characteristics of typical oxbow connecting middle reaches of Yangtze River

水文过程改变、物理形态收缩是制约长江中游天鹅洲与上车湾故道作为国家级保护物种重要迁地保护区高质量发展的主要因子。通过遥感解译提取两条故道1990~2021年逐年枯水期水域形态,识别主要形状参数,分析计算岸线发育系数(SDI)、形态发育系数(Φ)及收缩特征系数(R_(s))等,然后利用LASSO回归模型构建消除水域面积影响的形态参数序列,再利用PELT算法和分段拟合方法分析形态参数年际间变化规律。分析结果表明:闸控通江故道可用形态发育系数表征,自然通江故道可用收缩系数表征;闸控后天鹅洲故道牛轭湖化进程基本停滞,岸线逐渐趋向于简单及平滑;随着下荆江河道持续冲刷,上车湾故道牛轭湖化进程可能会逐步加速;建议采用水道疏浚、岸线整治、涵闸节制与调度等措施对故道形态进行保护。研究成果对于辨析三峡水库运行、闸控等对故道物理形态的影响具有指导意义。

Hydrological connectivity barriers and physical morphology shrinkage are the main factors restricting Tian′ezhou and Shangchewan oxbow′s role as important translocation protection areas for nationally protected species.Through remote sensing interpretation,the water morphology during dry seasons from 1990 to 2021 was extracted annually,and the main shape parameters were identified.Analysis of physical morphology parameters such as shoreline development coefficient(SDI),morphology development coefficient(Φ),and shrinkage coefficient(R_s)were conducted.A morphological parameter sequence eliminating the influence of water area was constructed using the LASSO regression model.The annual variation in morphological parameters were analyzed using the PELT algorithm and segmented fitting method.The gate regulated communication channel can be characterized by the morphological development coefficient,while the natural communication channel can be characterized by the shrinkage coefficient.The process of transformation of Tian′ezhou oxbow lake has basically stagnated after regulation,and the shoreline has gradually tended to become simpler and smoother.With the continuous scouring of the Shangchewan river channel,the process of oxbow lake transformation may gradually accelerate.It is recommended to adopt measures such as waterway dredging,shoreline improvement,sluice gate controlling and regulation to protect the morphology of the oxbow.The research results have guiding significance for the analysis on influence of the Three Gorges Reservoir operation and gate regulation on the physical form of oxbows.