1959—2018年九段沙地貌演化特征及动力机制

基于近60年（1959—2018年）系列水下地形资料，研究九段沙成形以来的地貌演化特征和动力成因。结果表明：九段沙1959—1990年处于稳速淤涨、以低滩为主的自然演化状态；近30年（1990—2018年），0 m及以上高滩受植被生长和长江口深水航道治理工程作用快速淤涨，-1~-2 m滩面受干扰程度小、稳速淤涨；近20年（1998—2018年），-3 m及以下低滩受流域减沙和临近的大型涉水工程影响淤涨放缓并由淤积转冲刷，期间流域减沙使得九段沙淤积放缓滩地由低到高向上延伸。未来流域来沙可能进一步下降并维持在较低水平，九段沙将面临-3 m及以下低滩进一步冲蚀，-3 m以上滩地淤积放缓并由低到高逐渐转冲的风险。

Morphological evolution and dynamic mechanics of the Jiuduansha Shoal (China) during 1959—2018

This paper studies the morphological evolution and dynamic mechanics of the Jiuduansha Shoal (China),based on analysis of bathymetric data over the last 60 years (1959—2018). The results show that from 1959 to 1990,a natural evolution trend with relatively stable accretion rates occurred for the Jiuduansha Shoal particularly in the lower intertidal zone. During the last 30 years(1990—2018),the high mudflat of 0 m above the chart datum was subjected to rapid accretion due to the plant development and the construction of the Yangtze Estuary deep-water channel regulation project. During the last 20 years(1998—2018),the low mudflat 3 m below the chart datum was affected by the decrease in the river sediment supply and the adjacent large-scale water-related projects. The accretion rates slowed down and instead sediment erosion became to occur. During this period,the sediment reduction in the river basin led the slow-accretion mudflat to move upward in the Jiuduansha Shoal. In the future,the sediment supply in the river basin may keep decreasing and maintain a lower level. The low mudflat 3 m below the chart datum in the Jiuduansha Shoal will face a risk of further erosion,and the rest will be subjected to a decreasing accretion or sediment erosion.