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Tide-surge interaction creates perturbations to storm surge at tidal frequencies and can affect the timing and magnitude of surge in tidally energetic regions. To date, limited research has identified high frequency tide-surge interaction (> 4 cycles per day) in coastal areas, and its significance in fluvial estuaries (where we consider it tide-surge-river interaction) is not well documented. Water level and current velocity observations were used to analyze tide-surge-river interaction at multiple tidal and overtide frequencies inside of a shallow estuary. Near the head of the estuary, higher frequency harmonics dominate tide-surge-river interaction and produce amplitudes more than double that of wind and pressure-driven surge. Bottom friction enhanced by storm-induced currents is the primary mechanism behind the interaction, which is further amplified by within-estuary resonance. High frequency tide-surge-river interactions in estuaries present a significant threat to human life, as the onset of flooding (in < 1.5 hrs.) is more rapid than coastal storm surge flooding. Commonly used storm surge forecasting models neglect high frequency tide-surge-river interaction and thus can markedly underestimate the magnitude and timing of inland storm surge flooding.
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Compound flooding in convergent estuaries: insights from an analytical model
Abstract. We investigate here the effects of geometric properties (channel depth andcross-sectional convergence length), storm surge characteristics, friction,and river flow on the spatial and temporal variability of compound floodingalong an idealized, meso-tidal coastal-plain estuary. An analytical model isdeveloped that includes exponentially convergent geometry, tidal forcing,constant river flow, and a representation of storm surge as a combination oftwo sinusoidal waves. Nonlinear bed friction is treated using Chebyshevpolynomials and trigonometric functions, and a multi-segment approach isused to increase accuracy. Model results show that river discharge increasesthe damping of surge amplitudes in an estuary, while increasing channeldepth has the opposite effect. Sensitivity studies indicate that the impactof river flow on peak water level decreases as channel depth increases,while the influence of tide and surge increases in the landward portion ofan estuary. Moreover, model results show less surge damping in deeperconfigurations and even amplification in some cases, while increasedconvergence length scale increases damping of surge waves with periods of 12–72 h. For every modeled scenario, there is a point where river dischargeeffects on water level outweigh tide/surge effects. As a channel isdeepened, this cross-over point moves progressively upstream. Thus, channeldeepening may alter flood risk spatially along an estuary and reduce thelength of a river estuary, within which fluvial flooding is dominant.
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- Award ID(s):
- 2013280
- PAR ID:
- 10417437
- Date Published:
- Journal Name:
- Ocean Science
- Volume:
- 18
- Issue:
- 4
- ISSN:
- 1812-0792
- Page Range / eLocation ID:
- 1203 to 1220
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/os-18-1203-2022
