长江口南汇嘴近岸海床近期演变分析——兼论长江流域来沙量变化的影响

The evolvement characteristics of Nanhuizui foreland in the Changjiang Estuary, China

长江口南汇嘴地处长江口和杭州湾的交汇处,是长江三角洲南翼向海延伸部分,是长江入海径流和泥沙进入杭州湾和东南沿海的主要输沙通道.在丰富的长江入海泥沙供应下,随着长江三角洲的向海伸展,南汇嘴近岸海床不断淤积.进入20世纪90年代,由于长江流域下泄泥沙的减少,引起南汇嘴近岸海床由淤积过程转向冲刷过程.此外,沿岸滩地的大规模的促淤造地工程,亦拦截了长江口入海的过境泥沙,从而加速近岸海床的冲刷.在今后相当长的一段时期内,随着长江流域大中型水库的不断兴建,长江入海泥沙量将持续保持在较低水平上,海床冲刷将不可逆转地持续下去,这应引起海洋工程建设部门的重视.

The Nanhuizui is located between the Changjiang Estuary and the Hangzhou Bay, is the prolongation in the south of Changjiang River Delta. It is the main passage of runoff and sediment transportation into the Hangzhou Bay and southeast coast. With the abundant sediment supply of the Changjiang River and the extension of Changjiang River Delta to the sea, the sea bed of this area was continually deposited before 1990. Because of the decrease of sediment flux from the Changjiang River after the 1990s, the sea bed near the Nanhuizui is eroded instead of deposit. On the other hand, projects such as land-making to accelerate the coastal deposit obstruct some passing sediment so that the erosion process has been speeded up. From now on, for some big projects in the Changjiang Estuary are under construction, the sediment flux into sea will keep in a low level in history, then the sea bed will be eroded sequentially and this phenomenon should be recognized by the related marine engineering departments.