山东青岛灵山湾南部海滩的时空演变及其影响因素*

全面准确评估海滩的时空演变,是海滩侵蚀防护的前提;基于卫星图像资源全面准确评估海滩的时空演变,对于缺乏长期连续实测数据的海滩的侵蚀防护具有重要意义。本研究基于谷歌地球引擎合成并下载灵南海滩(灵山湾南部海滩)1984—2021年的880幅卫星图像,聚焦海滩剖面提取干湿线和水边线在剖面上的位置;结合模拟潮位分析海滩剖面形态,计算海滩坡度和平均高、低潮线等,采用多指标研究灵南海滩的时空演变;结合历史资料分析影响灵南海滩演变的主要因素,并利用海滩实测数据评估利用卫星图像提取的海滩岸线的误差。结果表明,大量卫星图像的应用提高了研究结果的时间分辨率、精度和可靠性。在1984—2021年间,灵南海滩部分岸段发生了阶段性快速侵蚀,侵蚀速率为5.2~60 m/a,总侵蚀量达30~78 m,持续时间为0.5~11年,该快速侵蚀主要是挖沙、养殖场改建和废弃等人为因素造成的,风暴潮起次要的辅助作用。除上述快速侵蚀时段外,灵南海滩普遍发生慢速侵蚀,侵蚀速率一般小于2 m/a,这是相对海平面上升和河流入海泥沙锐减等的结果。

Spatial and temporal evolution of Lingnan Beach in Qingdao of Shandong Province and its influencing factors

Comprehensively and accurately assessing the spatial and temporal evolution of beaches is the premise of beach erosion protection. Comprehensively and accurately assessing the spatial and temporal evolution of beaches based on satellite imagery is of great significance to the erosion protection of beaches which lack long-term continuous measured data.In this paper,880 satellite images of Lingnan Beach from 1984 to 2021 were synthesized and downloaded from Google Earth Engine;the dry/wet line and waterline positions on transects were extracted using a method focusing on beach transects.Combined with simulated tidal heights,the beach profile morphology was analyzed. The beach slope,mean high and low tide lines were calculated,and the spatial and temporal evolution of Lingnan Beach was studied by using above multiple indicators. Combined with historical data,the main factors affecting the evolution of Lingnan Beach were analyzed,and the errors of the satellite-derived beach shorelines were evaluated using the measured data of the beach.The results show that the application of a large number of satellite images improves the temporal resolution,accuracy and reliability of the results. In 1984-2021,part of Lingnan Beach have experienced periodic rapid erosion with a rate of 5.2~60 m/a and a total amount of 30~78 m,lasting for about 0.5~11 years. The rapid erosion was mainly caused by human factors such as dredging sand,reconstruction and abandonment of aquaculture farms,while storm surges played a secondary role. Apart from rapid erosion periods,there was widespread slow erosion at Lingnan Beach,and the erosion rate was mostly less than 2 m/a,resulting from the relative sea level rise and the significant reduction of river discharged sediments into the sea.