Abstract
Low-lying coastal areas in the mid-Atlantic region are prone to compound flooding resulting from the co-occurrence of river floods and coastal storm surges. To better understand the contribution of non-linear tide-surge-river interactions to compound flooding, the unstructured-grid Finite Volume Community Ocean Model was applied to simulate coastal storm surge and flooding in the Delaware Bay Estuary in the United States. The model was validated with tide gauge data in the estuary for selected hurricane events. Non-linear interactions between tide-surge-river were investigated using a non-stationary tidal analysis method, which decomposes the interactions’ components at the frequency domain. Model results indicated that tide-river interactions damped semidiurnal tides, while the tide-surge interactions mainly influenced diurnal tides. Tide-river interactions suppressed the water level upstream while tide-surge interaction increased the water level downstream, which resulted in a transition zone of damping and enhancing effects where the tide-surge-river interaction was prominent. Evident compound flooding was observed as a result of non-linear tide-surge-river interactions. Furthermore, sensitivity analysis was carried out to evaluate the effect of river flooding on the non-linear interactions. The transition zone of damping and enhancing effects shifted downstream as the river flow rate increased.
Highlights
Coastal flooding hazards caused by tropical cyclones present a severe risk to nearly 40% of the U.S population living in low-lying coastal areas
This paper presents the results of a modeling study conducted to investigate the variations between tide-river interactions (TRIs), tide-surge interactions (TSIs), and Tide-surge-river interactions (TSRIs) and evaluate their interactions and their contributions to the total water levels (TWLs) during compound flooding events in the Delaware Bay Estuary (DBE)
Comparison of the TWL and unmodulated total water level (UTWL) indicates that modulations from TSRI on TWL vary with locations and extreme events
Summary
Coastal flooding hazards caused by tropical cyclones present a severe risk to nearly 40% of the U.S population living in low-lying coastal areas. The co-occurrence of storm surge and river flooding may cause compound flooding (Bevacqua et al, 2019), which results in extreme water levels caused by non-linear interactions of storm surges, river flood, and astronomical tides (Doodson, 1956; Proudman, 1957; Rossiter, 1961; Johns et al, 1985; Arns et al, 2020). The total water levels could be increased or decreased by the non-linear interactions between storm surges, river flow, and tides. Such non-linear interaction is sensitive to sea level rise, storm intensity, and river flow as a result of climate change (Yang et al, 2014; Li et al, 2020), which makes the flood hazard risk even more complex and unpredictable
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