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首页> 外文期刊>Estuarine Coastal and Shelf Science >Morphodynamics of nearshore rhythmic sandbars in a mixed-energy environment (SW France): 2. Physical forcing analysis
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Morphodynamics of nearshore rhythmic sandbars in a mixed-energy environment (SW France): 2. Physical forcing analysis

机译：混合能量环境中近岸有节奏沙洲的形态动力学（法国西南）：2.物理强迫分析

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The morphology and migration of rhythmic intertidal ridge and runnel systems, and subtidal crescentic bars that border the southwest coast of France were characterized using in situ surveys and maps obtained by remote-sensing methods. The period from 1986 to 2000 was investigated. A total of 35 km of coast was mapped. This data set shows several specificities, the origin of which are examined in the present report using hydrodynamic data. A complete analysis of the influence of wave climate on both the shape and the movements of these rhythmic sedimentary patterns was performed. In addition, SWAN and MORPHODYN-coupled numerical models were used to provide quantification of both wave breaking and longshore currents for wave parameters that were representative of the mean values and of the energetic conditions. This study demonstrated the short time response of intertidal systems to the wave forcing. When the offshore significant wave height (H_s) was lower than 2.5 m, regular coastal ridge and runnel systems developed in the intertidal zone and migrated in the longshore-drift direction at a rate of 1.7-3.1 m day~(-1). By contrast, the ridge and runnel system morphology abruptly changed when the H_s exceeded 2.5 m, and after the storm, the typical ridge and runnel rhythmic topography was recovered within 5-9 days. The crescentic bars, which had a convex seaward shape, were affected by waves with H_s values greater than 3 m (slightly less for short waves). Depending on the wave orientation, the crescentic bars moved in the longshore-drift direction at a rate that reached 1 m day~(-1). The data suggested a slight negative correlation between the mean alongshore length of the crescentic bar and the mean H_s. Finally, it seemed that increasing the wave obliquity with respect to the coast resulted in the flattening of the crescentic bars. Thus, coupling Spot and in situ mapping to hydrodynamic records allow the characterization of coastal morphology and dynamics, with time and space samplings that are particularly well adapted to the little studied alongshore morphodynamics. This approach should improve the difficult parameterization of morphodynamic models in high-energy environments.
机译：使用遥感方法获得的现场调查和地图，对有节奏的潮间垄和漏斗系统以及与法国西南海岸接壤的潮间带月牙形条的形态和迁移进行了表征。对1986年至2000年进行了调查。总共绘制了35公里的海岸。该数据集显示了几种特殊性，在本报告中使用流体力学数据检查了其起源。对波浪气候对这些有节奏的沉积模式的形状和运动的影响进行了完整的分析。另外，使用SWAN和MORPHODYN耦合的数值模型来提供代表平均值和高能条件的波浪参数的波浪破碎和近岸电流的量化。这项研究证明了潮间带系统对波浪强迫的短时响应。当离岸有效波高（H_s）小于2.5 m时，潮间带发育规则的海岸脊和漏斗系统，并以1.7-3.1 m day〜（-1）的速率向长岸漂移方向迁移。相比之下，当H_s超过2.5 m时，脊和漏斗的系统形态会突然改变，并且在暴风雨后，典型的脊和漏斗的节奏形貌在5-9天内得以恢复。新月形的条形呈凸的向海形状，受到H_s值大于3 m（短波的影响较小）的波的影响。取决于波浪的方向，新月形条以近岸漂移的方向移动，其移动速度达到1 m day〜（-1）。数据表明，新月形条的平均沿岸长度与平均H_s之间存在轻微的负相关。最后，似乎相对于海岸的海浪倾斜度增加导致新月形条变平。因此，将点测绘和原位制图耦合到水动力记录可以表征海岸的形态和动力学，而时间和空间采样尤其适合于很少研究的沿岸形态动力学。这种方法应该可以改善高能环境中形态动力学模型的参数设置难度。

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