We combine archival research, semi‐analytical models, and numerical simulations to address the following question: how do changes to channel geometry alter tidal properties and flood dynamics in a hyposynchronous, strongly frictional estuary with a landward decay in tidal amplitudes? Records in the Saint Johns River Estuary since the 1890s show that tidal range has doubled in Jacksonville, Florida. Near the estuary inlet, tidal discharge approximately doubled but tidal amplitudes increased only ∼6%. Modeling shows that increased shipping channel depths from ∼5 to ∼13m drove the observed changes, with other factors like channel shortening and width reduction producing comparatively minor effects. Tidal amplitude increases are spatially variable, with a maximum change 20–25 km from the estuary inlet; tidal theory suggests that increases in amplitude approximately follow , where x is the distance from the ocean and μ is a damping coefficient. Tidal changes are a predictor of altered surge dynamics: Numerical modeling of hurricane Irma under 1898 and 2017 bathymetric conditions confirms that both tidal and storm surge amplitudes are larger today, with a similar spatial pattern. Nonetheless, peak water levels are simulated to be larger under 1898 bathymetry. The cause is likely the record river discharge observed during the storm; as suggested by a subtidal water‐level model, channel deepening since 1898 appears to have reduced the average surface slope required to drain both mean river flow and storm flows toward the ocean. Nonetheless, results suggest an increased vulnerability to storms with less river flow, but larger storm surge.

中文翻译：

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河道加深对潮汐，河水排放效应和风暴潮的影响

我们将档案研究，半分析模型和数值模拟相结合，以解决以下问题：在不同步的强摩擦河口中，随着潮汐振幅的向后衰减，通道几何形状的变化如何改变潮汐特性和洪水动态？自1890年代以来在圣约翰斯河河口的记录显示，佛罗里达州杰克逊维尔的潮汐范围增加了一倍。在河口附近，潮汐排放量大约增加了一倍，但潮汐幅度仅增加了约6％。建模显示，运输通道深度从约5m增加到约13m，驱使观察到的变化，而其他因素（例如通道缩短和宽度减小）产生的影响则相对较小。潮汐振幅的增加在空间上是可变的，距河口入口的最大变化为20–25 km。，其中x是到海洋的距离，而μ是阻尼系数。潮汐变化是潮汐动力学变化的预测因素：1898年和2017年的等深线条件下的Irma飓风的数值模型证实，如今潮汐和风暴潮的振幅都更大，具有类似的空间格局。尽管如此，根据1898年的测深法，峰值水位被模拟为更大。原因可能是暴风雨期间观察到的创纪录的河流流量。正如潮下水位模型所建议的那样，自1898年以来的航道加深似乎减少了向海洋排放平均河流量和暴雨流量所需的平均地表坡度。但是，结果表明，河水流量较小但风暴潮较大的地区，对风暴的脆弱性增加。