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Satellite-derived shoreline detection at a high-energy meso-macrotidal beach
Geomorphology ( IF 3.9 ) Pub Date : 2021-03-20 , DOI: 10.1016/j.geomorph.2021.107707
Bruno Castelle , Gerd Masselink , Tim Scott , Christopher Stokes , Aikaterini Konstantinou , Vincent Marieu , Stéphane Bujan

Publicly available satellite imagery can now provide multi-decadal time series of shoreline data from local to global scale, enabling analysis of sandy beach shoreline variability across a spectrum of temporal scales. Such data can, however, be associated with large uncertainties, particularly for beaches experiencing a large tidal range (>2 m) and energetic incident waves. We use a decade of bi-monthly topographic surveys at the high-energy meso-macrotidal beach of Truc Vert, southwest France, and concurrent wave and water-level hindcast to investigate the uncertainties associated with satellite-derived time series of the shoreline position. We show that consideration of the water level and wave runup elevation is critical for accurately estimating waterline position and, in turn, shoreline position. At Truc Vert, including non-tidal water level residuals (e.g. wind-driven surge) and accounting for time- and elevation-varying beach slope for horizontal correction did not improve satellite-derived shoreline position. A new total water level threshold is proposed to maximize the number of usable images while minimizing errors. Accounting for wave runup and the new water level threshold at Truc Vert, the number of usable satellite images is doubled and shoreline position errors are at least halved compared to previous work at this site. Using the 1984–2019 reconstructed shoreline, we also show that the satellite-derived shoreline trends and interannual variability are in better agreement with field measurements. Although the approach proposed here needs to be tested on other sites in different tidal/wave forcing environments with different morphological and sediment characteristics, we anticipate that it will improve the temporal and spatial description of shoreline change on most surf tidal beaches where accurate continuous water level and wave hindcasts and/or observations are available.



中文翻译:

高能中微巨体海滩的卫星源海岸线探测

公开可用的卫星图像现在可以提供从本地到全球尺度的数十年时间序列的海岸线数据,从而可以分析整个时标范围内的沙滩海岸线变化。但是,此类数据可能具有较大的不确定性,尤其是对于潮汐范围较大(> 2 m)和高能入射波的海滩。我们在法国西南部的特鲁克维尔(Truc Vert)的高能中微巨体海滩进行了十年的双月地形调查,并发了海浪和水位同时预报,以调查与卫星派生的海岸线时间序列有关的不确定性。我们表明,水位和波浪上升高度的考虑对于准确估算水线位置以及海岸线位置至关重要。在Truc Vert,包括非潮汐水位残差(例如,风浪)和考虑随时间和海拔变化的海滩坡度进行水平校正的方法,并不能改善卫星派生的海岸线位置。提出了一个新的总水位阈值,以使可用图像的数量最大化,同时使误差最小。考虑到波浪加速和Truc Vert的新水位阈值,与该站点以前的工作相比,可用卫星图像的数量增加了一倍,海岸线位置误差至少减少了一半。使用1984-2019年重建的海岸线,我们还表明,卫星衍生的海岸线趋势和年际变化与实地测量更加吻合。

更新日期:2021-03-27
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