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首页> 外文期刊>Ocean & coastal management >Geometric properties of anthropogenic flood control berms on southern California beaches
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Geometric properties of anthropogenic flood control berms on southern California beaches

机译：加利福尼亚南部海滩上人为防洪堤的几何特性

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摘要

Coastal flood risk from coincident high tides and energetic waves is concentrated around low-lying urban areas. Municipalities construct temporary sand berms (also known as sacrificial dunes) to manage potential flooding, however the relationships between berm geometry (e.g., height, width and length) and performance are not understood. Concomitant pressures of sea level rise and urbanization will increase active beach berming. Effective future coastal flood risk management will depend upon optimizing berm efficacy relative to geometry, placement, and water levels. Here, 34 individual berms at seven southern California locations are characterized using 18 LiDAR datasets spanning nearly a decade. Three berm classifications emerged based on deployment duration: event, seasonal and persistent. Event berms, deployed to manage specific storms or high water events, are triangular in cross-section, relatively low volume (～4 m~3/m) and low crest elevation (～5 m NAVD88). Seasonal berms are larger, volumes vary from 6 to 28 m~3/m, and average crest elevations are between 5.3 and 6.4 m. A persistent berm, captured in all LiDAR data for that area, is the largest (48 m~3/m), longest (1.2 km), and highest mean crest elevation (7 m NAVD88) of all study berms. Total water levels, estimated using observed tides and a regional wave model coupled with an empirical runup formula, suggest that overtopping is rare. Currently, event berms are vulnerable to wave attack only a few hours per year. However, even with modest sea level rise (～25 cm) or El Nino conditions, exposure increases significantly, and substantial nourishments may be required to maintain current flood protection levels.
机译：高潮和高潮同时发生的沿海洪灾风险集中在低洼的城市地区。市政当局建造了临时的沙堤（也称为牺牲性沙丘）来管理潜在的洪水，但是人们对堤坝的几何形状（例如高度，宽度和长度）与性能之间的关系尚不了解。海平面上升和城市化带来的压力将增加活跃的海滩边缘。未来有效的沿海洪水风险管理将取决于优化护堤相对于几何形状，位置和水位的功效。在这里，使用横跨近十年的18个LiDAR数据集，对加利福尼亚南部七个位置的34个独立护堤进行了描述。根据部署持续时间，出现了三种护堤类别：事件，季节和持续时间。事件护堤的横截面为三角形，体积较小（〜4 m〜3 / m），波峰高低（NAVD88〜5 m），用于处理特定的暴风雨或高水位事件。季节性护堤较大，体积从6到28 m〜3 / m不等，平均波峰高度在5.3到6.4 m之间。在该区域的所有LiDAR数据中捕获的永久性护堤，是所有研究护堤中最大的（48 m〜3 / m），最长的（1.2 km）和最高的平均波峰高度（7 m NAVD88）。总水位是使用观察到的潮汐和区域波浪模型结合经验推升公式估算得出的，表明超顶现象很少见。当前，事件护堤每年仅几个小时容易受到波浪攻击。但是，即使在海平面上升（约25厘米）或厄尔尼诺现象的情况下，暴露量也会显着增加，并且可能需要大量营养来维持当前的防洪等级。

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