华南岬湾海滩冲淤演变特征及其机制分析—以南澳岛前江湾为例

岬湾海滩在华南地区普遍分布，众多海滩面临侵蚀退化问题，对其海滩冲淤演变特征及机制的研究具有重要的现实意义。本文以粤东重要的旅游海岛南澳岛南部的前江湾为研究区，利用滩面调查、遥感影像数据与历史海图和实测水深数据，研究1970—2022 年海滩冲淤特征，并从水动力、沿岸输沙、稳定岸线形态等方面，探讨人类活动对海滩冲淤演变的影响机制。结果表明：前江湾海滩蚀淤演变在东南沿岸码头防波堤海岸工程建设前后呈现不同的空间变化特征，切线岸段前期侵蚀、后期侵蚀加剧，弧形岸段前期淤积、后期侵蚀；人类海岸工程造成的岬角位置变化和沿岸输沙受阻是影响海滩蚀淤演变的主要机制，导致岬湾岸线平面形态变为不稳定状态，区域沉积物的亏损也加剧了海岸失衡；自东向西的沿岸输沙的不均衡对其海岸线演变的空间特征起控制作用。

Analysis on the Evolution and Mechanism of Headland-Bay Beaches in South China—A Case from Qianjiang Bay in the Nan’ao Island

In South China where headland-bay beaches are commonly developed along the coast and many beaches are currently facing erosion problems, the study of the erosion and accretion evolution characteristics and mechanisms of headland bay beaches has important practical significance. This study took Qianjiang Bay in the south of Nan’ao Island, an important tourist island in Guangdong Province, as the research area. On the basis of beach surveys, remote sensing image data, historical charts and measured water depth data, this study conducted research on the beach erosion and accretion characteristics from 1970 to 2022. This study also explored the impact of human activities on the beach evolution from the aspects of the hydrodynamics, the longshore sediment transport, and the equilibrium embayment planform. The results showed that, the beach evolution of Qianjiang Bay showed different spatial characteristics before and after the construction of the pier breakwaters along the southeast coast. The tangent bank section was eroded in the early stage and the erosion was intensified in the later stage, the arc bank section was silted in the early stage and eroded in the later stage. The change in the position of the headland and the obstruction of the longshore sediment transport caused by the human coastal projects were the main mechanisms affecting the beach evolution, causing the unstable planform of the headland-bay beach coastline. The loss of regional sediments also aggravated the coastal imbalance. The longshore sediment transport from east to west controlled the spatial characteristics of the coastline evolution.