长江口横沙浅滩冲淤演变特征分析

Analysis of the characteristics of erosion and accumulation evolution of the Hengsha Shoal in the Yangtze River Estuary

横沙浅滩作为长江口前沿滩涂湿地的重要组成部分,是“上海市长远发展战略空间”的预留区,掌握其滩涂演变规律对该地区的资源保护及合理开发具有重要的参考价值。基于2005—2021年长江口实测水下地形数据,定量分析研究了横沙浅滩地形演变过程,及其对周边河口工程建设和水沙条件变化的响应。研究结果表明:横沙浅滩近年来整体呈现“长高长不大”的演化格局,中、东部区域明显淤高,沙体向海延伸与河口泥沙滞流点的向外海移动关系紧密。流域输沙量锐减是横沙浅滩滞涨的重要原因,滩面北沿和深水航道北侧冲刷明显,造成N23堤顶冲坑的扩大与滩面潮水沟的贯通。深水航道工程与横沙东滩促淤圈围工程的建设是潮水沟与N23堤顶冲坑迅速发育的主要原因。

As an important component of the Yangtze River Estuary’s forefront tidal flat wetland,the Hengsha Shoal is a reserved area for the“long-term development strategic space”of Shanghai.Understanding its tidal flat evolution pattern is of great reference value for resource protection and rational development in the region.Based on the underwater topographic data from 2005 to 2021 of the Yangtze River Estuary,this study quantitatively analyzes the geomorphic evolution process of the Hengsha Shoal and its response to surrounding estuarine engineering construction and changes in water and sediment conditions.The research results indicate that in recent years,the overall evolution pattern of the Hengsha Shoal shows a trend of“elongation without enlargement”,with significant accumulation in the central and eastern regions.The extension of the sand body towards the sea is closely related to the outward movement of the estuarine siltation point.The sharp decrease in sediment transport in the basin is a significant reason for the shoal’s stagnation.Erosion is evident along the northern edge of the shoal and the north side of the deep-water channel,leading to the expansion of erosion pits on the N23 embankment and the connection of tidal creeks on the shoal surface.The construction of the deepwater channel project and the Hengsha East Shoal’s siltation-promoting enclosure project are the main reasons for the rapid development of tidal creeks and erosion pits on the N23 embankment.