近50年北海市海岸线变迁及其环境效应分析

Analyses on Shoreline Changes and Its Environmental Impacts in Beihai City Since the Last 50 Years, Guangxi, China

关键词:  海岸线变迁  遥感  北海市

Key words:  remote sensing  shoreline changes  Beihai City

摘要:

[目的]研究近50年来海岸线变迁的规律及其环境效应。[方法]以北海市1955-2004年遥感影像为数据源,并结合野外调查。[结果]南流江三角洲河口区沿岸海岸线变化最大。海岸线长度除1977-1988年略有增加外,整体上呈递减趋势,1998年至2004年变化减缓。北海市海岸线变化的环境效应表现为引起冲淤变化。[结论]海岸线变迁主要是受围海工程影响,海岸的自然侵蚀、淤积作用不明显,海岸线变化总体上是趋于平直,长度减少。环境效应变化较明显的是南流江三角州河口区河道改道导致河道自然冲刷拓宽、部分江心岛受到冲刷侵蚀;人工堤坝保护了海岸,但滩涂可能遭受侵蚀影响,或海浪翻腾沙滩底部影响了沙滩质量。

Abstract:

[Objective] The law of shoreline change and its environmental impact over the past 50 year was studied.[Methods] The remote-sensing images of Beihai City from 1955 to 2004 were used as data sources and combined with field surveys.[Results] The results showed that the shoreline along the delta estuary area of Nanliujiang River changed most.The shoreline length had increased slightly from 1977 to 1988, but it had shown a trend of decline in general and changed slowly from 1998 to 2004.The environmental effect of coastal changes in Beihai City manifested as causing change in erosion and siltation.[Conclusion] Shoreline changes in Beihai City were mainly affected by coast reclamation works.The effects of natural erosion and deposition of the coast were not obvious.The shoreline generally became flat and reduced in length.The most obvious change in the environmental effect was the channel realignment of the delta estuary area of Nanliujiang River, which led to that the river was widened through self-scouring and part of the central island suffered from scouring and erosion.Although artificial dams protected the coast, the tidal flats might be affected by erosion, and the beach quality was affected owing to that the waves rolled over the bottom of the beach.