Longshore Transport at Cape Lookout, North Carolina: Shoal Evolution and the Regional Sediment Budget
Longshore Transport at Cape Lookout, North Carolina: Shoal Evolution and the Regional Sediment Budget
复制标题
北卡罗来纳州卢考特角的沿岸运输：浅滩演化和区域沉积物预算
作者：
Jun–Yong Park;J. Wells
摘要自从19世纪第一次进行初步的野外研究以来，海角了望尖前陆经历了显著的近海加积。尽管波为主的设置，但是，鲜为人知的是沿岸的过程下的广泛的波的条件下，影响复杂的海岸几何形状在海角。在这项研究中，我们研究了沿岸的过程，驱动沿岸流，使用数值波浪折射/衍射模型（参考文献/DIF 1），并通过使用航空照片和海图。结果表明，沿岸流的方向和速度，正如预期的那样，是高度可变的，主要取决于传入波的方向。在东北和东波方法下，核心银行上的南部沿岸流占主导地位，而东南和南波方法下产生较弱的北部流。这些模式的结果为Cape Lookout Shoal提供了沉积物来源。结果表明，从岩心库到浅滩的沉积物输入量为512，000至581，000 m3/年。该系统的西翼接收了这些沉积物的一部分，这些沉积物从浅滩释放出来，并被从东南、南部和西南方向接近的波浪向北输送。预测的沿岸流的浅滩上表明，反复的延伸和退缩的海角了望点将导致的不平衡偏南沿岸流的浅滩东侧和偏北沿岸流的西侧。Cape Lookout Shoal可能通过干扰向岸波的传播和允许波将能量集中到其离岸水下区域，在保护邻近屏障岛屿的部分方面发挥作用。然而，尚不清楚浅滩北方近端区域的沉积物是如何被输送到更南部的远端区域的。
Abstract The Cape Lookout cuspate foreland has undergone significant offshore accretion since the first rudimentary field studies were conducted in the 1800s. Despite the wave-dominated setting, however, little is known about littoral processes under the wide range of wave conditions that impact the complicated coastal geometry at the cape. In this study we examined littoral processes, driven by longshore currents, using a numerical wave refraction/diffraction model (Ref/Dif 1) and through use of aerial photographs and nautical charts. Results show that longshore current direction and speed, as expected, are highly variable and depend primarily on incoming wave direction. Southerly longshore currents on Core Banks predominate under northeast and east wave approaches, whereas weaker northerly currents are generated under southeast and south wave approaches. The result of these patterns provides a source of sediments to Cape Lookout Shoal. Results show the sediment input from Core Banks to the shoal is of the order 512,000 to 581,000 m3/yr. The western limb of the system receives a portion of these sediments, which are released from the shoal and transported north by waves that approach from the southeast, south, and southwest. Predicted longshore currents on the shoal indicate that repeated extension and retreat of Cape Lookout Point would result from the imbalance between southerly longshore currents on the east side of the shoal and northerly longshore currents on the west side. Cape Lookout Shoal may play a role in protecting sections of adjacent barrier islands by interfering with shoreward wave propagation and by allowing waves to focus energy onto their offshore subaqueous areas. It is still unclear, however, how sediments on the northern proximal regions of the shoal are transported to the distal regions farther south.