Abstract Groundwater is a major component of the water cycle in the river-deltaic environment. However, the dynamics of groundwater flows in the river delta remains an open question owing to the complexities in the hydrologic and geological settings. This study employed a hydrogeological modeling approach to investigate groundwater dynamics in the Mississippi River Delta (MRD). A detailed groundwater model for the top 50 m of the MRD was constructed from the Head of Passes (RK 0) to Jesuits Bend (RK 108) using geotechnical borings and topobathymetric maps. Mississippi River stage and tide stage data were the key hydrologic data, which reflect hydrologic forcing (floods, storms, and hurricanes) to the groundwater system. By investigating the 2012 hydrologic year, the study presents several intriguing findings. Groundwater discharge and recharge rates to the river and surrounding bays were estimated 3 or 4 orders of magnitude smaller than Mississippi River discharge rate to the Gulf of Mexico. Nevertheless, the model showed strong surface-groundwater interactions controlled by local hydraulic gradient at the river and bay interfaces during severe hydrologic events. Specifically, during Hurricane Isaac pore water pressure was estimated 4–6 times higher than the normal condition and peak groundwater recharge was reached due to storm surges. Peak groundwater discharge sharply occurred a few days later after the hurricane passed. The study found such a dramatic change in surface-groundwater interactions was due to quick surface water receding and delayed groundwater response. As a consequence, more areas are likely exposed to harmful high pore water pressure and low factor of safety condition, which would destabilize sediments, enhance erosion, and compromise safety of coastal infrastructures such as the ring levees.

中文翻译：

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了解密西西比河三角洲地下水流的动态

摘要 地下水是河流三角洲环境中水循环的重要组成部分。然而，由于水文和地质环境的复杂性，河流三角洲地下水流动的动态仍然是一个悬而未决的问题。本研究采用水文地质建模方法来调查密西西比河三角洲 (MRD) 的地下水动态。MRD 顶部 50 m 的详细地下水模型是使用岩土钻孔和地形测深图从通道头 (RK 0) 到耶稣会士弯 (RK 108) 构建的。密西西比河水位和潮位数据是关键的水文数据，反映了地下水系统的水文强迫（洪水、风暴和飓风）。通过调查 2012 水文年，该研究提出了几个有趣的发现。河流和周围海湾的地下水排放和补给率估计比密西西比河向墨西哥湾的排放率小 3 或 4 个数量级。然而，该模型显示出在严重水文事件期间受河流和海湾界面局部水力梯度控制的强烈地表-地下水相互作用。具体来说，在艾萨克飓风期间，孔隙水压力估计比正常情况高 4-6 倍，并且由于风暴潮达到了地下水补给峰值。飓风过去几天后，地下水流量急剧上升。研究发现地表-地下水相互作用发生如此巨大的变化是由于地表水快速后退和地下水响应延迟。作为结果，