杭州湾北岸金山深槽侵蚀-淤积状态研究

Erosion and Deposition State of the Jinshan Through at the North Bank of Hangzhou Bay

利用1989—2018年杭州湾北岸金山咀邻近区金山深槽实测地形资料以及2005—2018年高分辨率断面测量数据,分析了金山咀前沿深槽动力地貌变化过程及其影响缘由。结果表明:①金山深槽区受杭州湾北岸侵蚀/淤积波的影响展现出淤积-冲刷的周期性循环变化,但整体以侵蚀为主,且30 a间总冲刷厚度超过2.4 m;②金山深槽面积与体积呈增长扩大的状态,年均增长率分别为0.32 km^(2)/a和1.94×10^(6) m^(3)/a,这与长江入海泥沙量的急剧减少密切相关;③金山深槽重心大致在城市沙滩前沿摆动,在NE—SW方向上运移但整体变化幅度不大。然而,因深槽面积扩大而引起深槽与堤岸之间的边坡处于不稳定状态,若金山深槽进一步向岸移动则金山咀附近岸段的稳定性将面临巨大风险。

Based on the regional measured bathymetric data during 1989-2018 and the field profile observation during 2005-2018,this study analyzed the morphodynamic processes and associated evolution mechanism of the Jinshan Trough of the north bank of Hangzhou Bay.The results show that:①Affected by erosion/siltation waves on the north bank of Hangzhou Bay,the Jinshan Trough has experienced a cyclic process of deposition and erosion,which mainly present eroded features with total erosion thickness over 2.4 m in recent thirty years;②There is an extension trend in both area and volume of the Jinshan Through.The average annual increasing rate of area and volume is 0.32 km^(2)/a and 1.94×10^(6) m^(3),respectively.The decreasing sediment discharge from the Yangtze River was responsible for the area and volume extension of Jinshan Through;③The barycenter of the Jinshan Trough basically oscillates around the front of the City Beach,with a weak movement extent in southwest-northeast direction.The slope between the Jinshan through and the embankment is in an unstable state due to the expansion of the through.And the bank near the Jinshanzui will face a huge risk in the bank stability if Jinshan Through keeps moving shorewards.