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Coastal flooding generated by ocean wave- and surge-driven groundwater fluctuations on a sandy barrier island
Journal of Hydrology ( IF 5.9 ) Pub Date : 2021-09-11 , DOI: 10.1016/j.jhydrol.2021.126920
Rachel Housego 1, 2 , Britt Raubenheimer 2 , Steve Elgar 2 , Sandy Cross 3 , Christian Legner 3 , David Ryan 4
Affiliation  

Three years of observations of groundwater elevations, ocean tides, surge, and waves, and rainfall are used to study coastal groundwater-driven flooding along the ocean side of a barrier island. Increases in surge and wave-driven water levels (setup) during 26 ocean storms with little rainfall, including the passage of 3 hurricanes, caused O(1 m) increases in groundwater heads under the dunes on the ocean side of the island, nearly double previously reported magnitudes. The inland propagation of the resulting pulses in groundwater levels is consistent with an analytical model (without recharge) based on shallow aquifer theory (Nash Sutcliffe model efficiencies of >0.7, maximum water-table level estimates within 0.1 m of observations). Infiltration of precipitation results in approximately a threefold increase in the groundwater level relative to the amount of rainfall. The analytical model (with recharge) driven with estimated ocean shoreline water levels (based on the 36-hr-averaged offshore tide, surge, and wave height) and measured precipitation predicts the maximum water-table height within 0.15 m of that observed across the barrier island during Hurricane Matthew, which was the only wave event during the 3-yr data set with more than 0.1 m rainfall.

Citizen-science reports from a smartphone app (iFlood) are used to evaluate the regional application of the model. Twenty-five ocean-side reports associated with 7 ocean storms (6 of which had minimal rainfall) between Sept 2019 and Feb 2020 showed flooding on natural (permeable) land surfaces along 70 km of the northern Outer Banks barrier island, from Corolla to Rodanthe, NC. The analytical model (with recharge) predicts flooding that is consistent with the timing and location for 19 of the 25 reports. Applying the model regionally suggests that more than 10% of the land area on the ocean side of the northern Outer Banks would be inundated by coastal groundwater even in the absence of rainfall for an ocean storm that generates a 2.25 m increase in the shoreline water level.



中文翻译:

沙障岛上由海浪和浪涌驱动的地下水波动产生的沿海洪水

对地下水高程、海洋潮汐、潮汐、波浪和降雨的三年观测被用于研究沿屏障岛海洋一侧的沿海地下水驱动的洪水。在 26 次降雨量很少的海洋风暴期间,包括 3 次飓风的通过,浪涌和波浪驱动的水位(设置)增加,导致O(1 m) 岛屿海洋一侧沙丘下的地下水水头增加,几乎是先前报告的两倍。产生的地下水位脉冲的内陆传播与基于浅层含水层理论的分析模型(无补给)一致(Nash Sutcliffe 模型效率 > 0.7,最大地下水位估计值在 0.1 m 观测范围内)。降水的入渗导致地下水位相对于降雨量增加了大约三倍。分析模型(带补给)由估计的海洋海岸线水位(基于 36 小时平均近海潮汐、潮汐和波浪高度)和测量的降水驱动,预测最大水位高度在 0.15 m 范围内观察到的水位高度范围内马修飓风期间的障壁岛,

来自智能手机应用程序 (iFlood) 的公民科学报告用于评估模型的区域应用。与 2019 年 9 月至 2020 年 2 月之间的 7 场海洋风暴(其中 6 场降雨量极少)相关的 25 份海洋报告显示,从卡罗拉到罗丹特的北外滩障岛沿线 70 公里的天然(可渗透)陆地表面发生洪水,数控。分析模型(带补给)预测的洪水与 25 份报告中 19 份的时间和地点一致。在区域范围内应用该模型表明,即使没有降雨导致海岸线水位增加 2.25 m 的海洋风暴,外滩北部海洋一侧超过 10% 的陆地面积也将被沿海地下水淹没.

更新日期:2021-10-02
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