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Predictable changes in extreme sea levels and coastal flood risk due to long‐term tidal cycles

Predictable changes in extreme sea levels and coastal flood risk due to long‐term tidal cycles
Predictable changes in extreme sea levels and coastal flood risk due to long‐term tidal cycles

We demonstrate that long-term tidally induced changes in extreme sea levels affect estimates of major flood hazard in a predictable way. Long-term variations in tides due to the 4.4 and 18.6-year cycles influence extreme sea levels at 380 global tide gauges out of a total of 581 analyzed. Results show coherent regions where the amplitudes of the modulations are particularly relevant in the 100-year return sea level, reaching more than 20 cm in some regions (western Europe, north Australia, and Singapore). We identify locations that are currently in a positive phase of the modulation and therefore at a higher risk of flooding, as well as when (year) the next peak of the long-term tidal modulations is expected to occur. The timing of the peak of the modulation is spatially coherent and influenced by the relative importance of each cycle (4.4 or 18.6-year) over the total amplitude. An evaluation of four locations suggests that the potentially flooded area in a 100-year event can vary up to ∼45% (in Boston) as a result of the long-term tidal cycles; however, the flooded area varies due to local topography and tidal characteristics (6%–13%). We conclude that tidally modulated changes in extreme sea levels can alter the potentially inundated area in a 100-year event and that the traditional, fixed 100-year floodplain is inadequate for describing coastal flood risk, even without considering sea-level rise.

extreme sea levels, flood hazard, flood mapping, nodal cycle, tide
2169-9275
Enríquez, Alejandra R.
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Wahl, Thomas
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Baranes, Hannah E.
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Talke, Stefan A.
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Orton, Philip M.
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Booth, James F.
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Haigh, Ivan D.
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Enríquez, Alejandra R.
8f3d3f7a-5879-4b61-bac6-85ab386975e7
Wahl, Thomas
6506794a-1f35-4803-b7f7-98702e57e667
Baranes, Hannah E.
9966d567-8406-4440-851c-83308bd6fa87
Talke, Stefan A.
e5df0d60-d93e-457f-939b-07fc4983efc5
Orton, Philip M.
1f31d7a7-c84c-4685-a760-2c5c36dbac31
Booth, James F.
c01f018f-09b9-4819-98c1-18e4e5ae2f60
Haigh, Ivan D.
945ff20a-589c-47b7-b06f-61804367eb2d

Enríquez, Alejandra R., Wahl, Thomas, Baranes, Hannah E., Talke, Stefan A., Orton, Philip M., Booth, James F. and Haigh, Ivan D. (2022) Predictable changes in extreme sea levels and coastal flood risk due to long‐term tidal cycles. Journal of Geophysical Research: Oceans, 127 (4), [e2021JC018157]. (doi:10.1029/2021JC018157).

Record type: Article

Abstract

We demonstrate that long-term tidally induced changes in extreme sea levels affect estimates of major flood hazard in a predictable way. Long-term variations in tides due to the 4.4 and 18.6-year cycles influence extreme sea levels at 380 global tide gauges out of a total of 581 analyzed. Results show coherent regions where the amplitudes of the modulations are particularly relevant in the 100-year return sea level, reaching more than 20 cm in some regions (western Europe, north Australia, and Singapore). We identify locations that are currently in a positive phase of the modulation and therefore at a higher risk of flooding, as well as when (year) the next peak of the long-term tidal modulations is expected to occur. The timing of the peak of the modulation is spatially coherent and influenced by the relative importance of each cycle (4.4 or 18.6-year) over the total amplitude. An evaluation of four locations suggests that the potentially flooded area in a 100-year event can vary up to ∼45% (in Boston) as a result of the long-term tidal cycles; however, the flooded area varies due to local topography and tidal characteristics (6%–13%). We conclude that tidally modulated changes in extreme sea levels can alter the potentially inundated area in a 100-year event and that the traditional, fixed 100-year floodplain is inadequate for describing coastal flood risk, even without considering sea-level rise.

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Accepted/In Press date: 18 March 2022
e-pub ahead of print date: 21 March 2022
Published date: April 2022
Additional Information: Funding Information: This work was funded by NSF PREEVENTS Award Numbers 1854896 (T. Wahl and A. R. Enriquez), 94267271 (J. F. Booth), 1855037 (P. M. Orton) and 2013280 (S. A. Talke). S. A. Talke was also funded by the National Science Foundation Award Numbers 1455350. A. R. Enr?quez was also funded byMarie Sk?odowska-Curie Actions, project 101019470 - SpaDeRisks. Funding Information: This work was funded by NSF PREEVENTS Award Numbers 1854896 (T. Wahl and A. R. Enriquez), 94267271 (J. F. Booth), 1855037 (P. M. Orton) and 2013280 (S. A. Talke). S. A. Talke was also funded by the National Science Foundation Award Numbers 1455350. A. R. Enríquez was also funded byMarie Skłodowska‐Curie Actions, project 101019470 ‐ SpaDeRisks. Publisher Copyright: © 2022. American Geophysical Union. All Rights Reserved. Copyright: Copyright 2022 Elsevier B.V., All rights reserved.
Keywords: extreme sea levels, flood hazard, flood mapping, nodal cycle, tide

Identifiers

Local EPrints ID: 457358
URI: http://eprints.soton.ac.uk/id/eprint/457358
ISSN: 2169-9275
PURE UUID: 9ba7ed6d-11d0-4553-bc93-81a04275b5eb
ORCID for Ivan D. Haigh: ORCID iD orcid.org/0000-0002-9722-3061

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Date deposited: 01 Jun 2022 16:45
Last modified: 06 Jul 2022 04:01

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Contributors

Author: Alejandra R. Enríquez
Author: Thomas Wahl
Author: Hannah E. Baranes
Author: Stefan A. Talke
Author: Philip M. Orton
Author: James F. Booth
Author: Ivan D. Haigh ORCID iD

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