温州瓯飞浅滩海域悬沙输运特征及其来源探讨

Discussion on characteristics of suspended sediment transport and source in sea area adjacent Wenzhou Oufei Shoal

基于2011年温州市瓯飞浅滩海域冬、夏季大、小潮共4次大面同步海流和悬沙观测资料,利用统计和物质长期输运机制分解方法,初步分析研究海域悬沙时空分布和水体、悬沙三维输运特征。结果表明,海域悬沙浓度平面上呈现近岸高、外海低,高浓度区出现于河口,浅滩外沿存在相对低值区的分布格局;垂向分布受复杂水动力(包括波浪、潮流、径流和沿岸流等)影响具有准直线型、抛物线型以及混合型分布等多种分布形态,且底层悬沙浓度与流速变化趋势具有虽同步但存在一定滞后的特性。水体与悬沙长期输运受径流、风生表层流、闽浙沿岸流等多种作用影响,存在明显季节变化和区域特征;其中河口站因径流作用表层输运强度大于其它区域,中底层泥沙由于波流共同作用影响、河口区显著的潮泵效应使得冬、夏季输运特征迥异;浅滩站表层水沙输运主要受风生表层流影响,中、底层的悬沙因潮致余流作用多指向岸线,外海受闽浙沿岸流的影响加强,垂向上输运强度差异减小。浅滩海域泥沙的主要来源为海域来沙(浙江沿岸流输沙和外海沉积水下沙洲的再搬运)和瓯江、飞云江的河流陆域输沙。

During winter and summer of 2011, simultaneous current and suspended sediment investigations in the sea area adjacent the Wenzhou Oufei Shoal were carried out in both spring and neap tide. Based on the da- ta, mathematical statistics and transport mechanism decomposition methods are used to preliminary analysis of characteristics of suspended sediment distribution and 3：D water and suspended sediment transport. The re- sults indicate that the suspended sediment concentration gradually decreased from offshore to open seas, and high-ratio turned up in the estuary, while the low-value center appeared at the outboard of shores. On account of the complex hydrodynamic conditions （including waves, tides, runoff and alongshore currents, etc. ）, the vertical distribution forms included quasi-linear type, parabolic type and mixing type and so on. The variation trend of suspended sediment concentration and current velocity near the bottom displayed consistent, but hys- teretic quality. Influenced by runoff, wind-driven surface currents and alongshore currents etc. , the transport of water and sediment showed significant seasonal variation and regional features. In the estuary, suspended sediment transport of the surface layer was larger than other areas because of runoff-effect, and the joint func- tion of currents and waves and outstanding tide-pump effect made the transport features in winter and in sum- mer disparate in middle and bottom layers. The surface water and sediment transport near the shoal was mainly affected by wind-driven surface currents, while most of the middle and near bottom sediment moved to the shoreline due to the tide-induced residual current. Due to the influence of alongshore current, the vertical transport difference gradually decreased in open waters. Furthermore, the suspended sediment of the seas mainly came from the runoff and open seas （including Zhejiang alongshore current, re-suspended and re-transported bottom sediment）.