地理学报 ›› 1997, Vol. 64 ›› Issue (S1): 170-178.doi: 10.11821/xb1997S1019

• 论文 • 上一篇    下一篇

香港大屿山岛南岸沙坝海滩的动力地貌变化

王为, 章典   

  1. 香港大学地理地质学系,香港
  • 出版日期:1997-12-15 发布日期:1997-12-15

MORPHODYNAMIC CHANGES OF BAY BARRIER BEACHES ON THE SOUTH COASTS OF LANTAU ISLAND, HONG KONG

Wang Wei, Zhang Dian   

  1. Department of Geography and Geology, the University of Hong Kong, Hong Kong
  • Online:1997-12-15 Published:1997-12-15

摘要: 深入海湾的沙坝海滩,其侵蚀与堆积主要表现为海滩泥沙的横向运动,纵向运动仅出现在潮汐通道附近。而在宽阔的海湾内,海滩横向与纵向的泥沙运动同样重要;沙坝海滩的形态随着海滩沿岸波高、沉积物特征和外滨地形的不同而变化。在东亚季风和香港当地的波浪和海岸输沙条件下,沙坝海滩具有冬季稳定、夏初堆积和夏末侵蚀的年变化。同时由于沉积物来源有限,海滩体积小,海滩对海岸环境的突然变化反应敏感,而具有无规律的变化。

关键词: 香港海岸, 海滩剖面, 海滩变化, 侵蚀与堆积

Abstract: Three bay barrier beaches in Pui O, Mui Wo and Cheung Sha bays on the south coast of Lantau Island, Hong Kong were selected as examples for the study of morphodynamic changes of bay barrier beaches on the Hong Kong coasts. The selected beaches were studied by means of geomorphology and sedimentology including the analysis of two years longshore and cross-shore variations of beach morphology in association with the changes of grain size and cusp spacing along the beaches in the same period.The study shows that firstly, according to the directions of arriving refracted waves, the sediment process on the bay barrier beaches is different in the deep and shallow indented bays. In deep indented bays,the sand movements on the bay barrier beaches are mainly in an on-shore/offshore direction with the longshore movement near the stream outlets. Both lateralsediment movements and onshore/off shore ones are of similar importance for the beach process in a shallow bay.Secondly, under the condition of a tidal range larger than wave heights on the Hong Kong coasts, the profiles vary along each beach in the bays due to a longshore variation in wave heights, offshore width and sediment grain size. In places where the wave heights are small, sediments are not well sorted and the sediment supply is sufficient to build up a wide and shal-low offshore, the beach profiles are characterized by a high tide beach, which has a relatively steep beach face, termimated rather abruptly at its base by a wide low-tide terace, a low tide beach. The high tide beach slope becomes gentle connecting at its foot to the low tide beach without the abrupt change, while the wave heights increase reducing the difference between the tidal range and wave heights. If the sediment supply is not sufficient supply is not suffi-cient , the beach slope will become steep, even the difference between the tidal range and wave height is small.Finally, under the local geological, monsoon climatic and wave conditions, the barrier beaches in Hong Kong have a very regular yearly change in sand movements which can be summarized as a tendency for late summer cut followed by a stable period in winter and early summer fill. However, the barrier beaches in Hong Kong may also have irregular changes in response to abrupt changes in coastal environment, such as big storm waves attacks or human impacts on the beaches, because of the beaches developing based mainly on the materials from the inland strems, which are limited resulting in the bay barriers and beaches on the Hong Kong coasts having formed in small size.

Key words: Hong Kong coast, beach profile, beach change, erosion and accretion

中图分类号: 

  • P737.1