摘 要：滨岸带作为水陆生态系统的关键过渡区，对维护河湖生态安全具有屏障作用，其空间识别与动态监测是流域水生态保护与空间管控的重要基础。以长江中下游（宜昌至入海口）为研究区域，基于Google Earth Engine（GEE）平台，利用多时相Sentinel-2影像构建水淹频率指数，并通过阈值分区方法划定水位变幅区内外边界，提出了一种适用于大尺度河流的滨岸带遥感划定方法。结果表明：（1）综合考虑岸线合理开发与生态空间保护的双重要求，划定的长江中下游滨岸带平均宽度为608m，流经城市滨岸带宽度为289m～982m；（2）生态岸带比为45.9%，空间上呈现出“中游优于下游、右岸高于左岸、水位变幅区优于陆域缓冲区”的分布格局，各流经城市生态岸带比为32%～66%；（3）滨岸带开发利用率为54.1%，以农业用地（33.7%）和工矿用地（7.2%）为主；约87km的硬质护岸工程集中分布于下游地区，显著削弱了自然水陆交互过程；（4）2022—2023年，生态用地净减少6.6km2，滨岸带仍面临“生态退、人工进”的发展趋势。研究表明，基于水淹频率阈值的遥感方法可实现滨岸带范围的连续化、自动化识别，为流域尺度滨岸带动态监测、水生态评估与空间管理提供了技术支撑，对滨岸带生态空间保护具有重要参考价值。

Objective: The riparian zone serves as a critical ecotone between terrestrial and aquatic ecosystems, playing a vital role in maintaining riverine ecological security and regulating water-land interactions. Accurate delineation and dynamic monitoring of riparian zones are fundamental for watershed-scale ecological protection and spatial management. Method: This study developed a novel remote sensing method for large-scale riparian zone delineation based on the inundation frequency index, leveraging multi-temporal Sentinel-2 imagery and the Google Earth Engine (GEE) platform. By constructing a water inundation frequency index and implementing a threshold-based partitioning approach, we objectively defined the inner and outer boundaries of the water-level fluctuation zone in the middle-lower reaches of the Yangtze River. Result: (1) the delineated riparian zone has an average width of 608 m, ranging from 289 m to 982 m across different urban sections; (2) the ecological riparian ratio is 45.9%, exhibiting distinct spatial patterns of “middle reaches > lower reaches”, “right bank > left bank”, and “water-level fluctuation zone > terrestrial buffer zone”; (3) the development utilization rate of riparian zones reaches 54.1%, primarily occupied by agricultural land (33.7%) and industrial-mining land (7.2%); (4) approximately 87 km of hardened embankments are concentrated in the lower reaches, substantially impairing natural land-water interactions. Furthermore, we observed a net reduction of 6.6 km2 in ecological land area during 2022-2023, indicating a continuing trend of “ecological retreat and artificial expansion”. Conclusion: This study confirms that the inundation frequency-based remote sensing method enables continuous, automated, and large-scale delineation of riparian zones, providing robust technical support for watershed-scale ecological assessment and spatial management strategies.