TY - JOUR
T1 - Predictable Changes in Extreme Sea Levels and Coastal Flood Risk Due To Long-Term Tidal Cycles
AU - Enríquez, Alejandra R.
AU - Wahl, Thomas
AU - Baranes, Hannah E.
AU - Talke, Stefan A.
AU - Orton, Philip M.
AU - Booth, James F.
AU - Haigh, Ivan D.
N1 - Publisher Copyright:
© 2022. American Geophysical Union. All Rights Reserved.
PY - 2022/4
Y1 - 2022/4
N2 - 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.
AB - 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.
KW - extreme sea levels
KW - flood hazard
KW - flood mapping
KW - nodal cycle
KW - tide
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U2 - 10.1029/2021JC018157
DO - 10.1029/2021JC018157
M3 - Article
AN - SCOPUS:85128849384
SN - 2169-9275
VL - 127
JO - Journal of Geophysical Research: Oceans
JF - Journal of Geophysical Research: Oceans
IS - 4
M1 - e2021JC018157
ER -