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利用北部湾海域1987-2013年7个时期多时序遥感影像为信息源,通过提取水体指数并以最大类间方差法计算水陆分割阈值,从而分割得到“水边线”并进行潮位校正后得到海岸线;对各时期海岸线的时空分布、分形维数、变迁速率等特征进行计算,并初步分析了海岸线变化的驱动力。研究结果表明:从1987-2013年北部湾海岸线增加120km,其中:北海市增加65km,防城港市增加54km,钦州市保持稳定。海岸线分维数从1.0677增加至1.0870,与海岸线长度变化趋势相同;从空间上看,北海、钦州、防城港段海岸线分维数逐渐增大,说明了北部湾海岸线由东向西逐渐变得曲折与复杂。从海岸线变迁的速率来看,总体变化速率为3.48m/a,77.30%的岸段变化速率低于平均值(保持稳定),22.70%的岸段变化速率远高于平均值(变化剧烈);从海岸线变迁的方向来看,约68.20%的岸段向海推(淤)进,约27.30%的岸段保持稳定,仅有约4.50%的岸段向陆侵蚀。人类生产建设活动是引起北部湾海岸线变化的主要驱动力,河口淤积与水力侵蚀对海岸线影响较小。
Using the multi-temporal remote sensing images of Beibu Gulf waters from 1987 to 2013 as the information source, the water body index was extracted and the land-water partitioning thresholds were calculated by the maximum-variance method to divide the waterline and get the tide level correction Coastline. The spatial-temporal distribution, fractal dimension, change rate and other characteristics of the coastline in each period are calculated, and the driving force of coastline change is analyzed. The results show that from 1987 to 2013, the Beibu Gulf coastline increased by 120km, of which: Beihai increased 65km, Fangchenggang increased 54km, Qinzhou remained stable. The fractal dimension of the coastline increased from 1.0677 to 1.0870, which is the same as that of the coastline. From the spatial point of view, the fractal dimension of the coastline in Beihai, Qinzhou and Fangchenggang gradually increased, indicating that the Beibu Gulf coastline gradually becomes tortuous from east to west and complex. In terms of the rate of coastline change, the overall rate of change was 3.48m / a, that of 77.30% was below the average (stable), and that of the rate of 22.70% was much higher than the average (dramatic changes). Seen from the direction of coastline change, about 68.20% of the shore sections pushed into the sea, about 27.30% of the shore sections remained stable, and only about 4.50% of the shore sections eroded toward the shore. Human production and construction activities are the major driving forces that cause the coastline of Beibu Gulf to change. Silt siltation and hydraulic erosion have less impact on the coastline.