The timing of decreasing coastal flood protection due to sea-level rise
Tim H.J. Hermans (NIOZ Royal Netherlands Institute for Sea Research, Universiteit Utrecht, TU Delft - Physical and Space Geodesy)
Víctor Malagón-Santos (NIOZ Royal Netherlands Institute for Sea Research)
Caroline A. Katsman (TU Delft - Environmental Fluid Mechanics)
Robert A. Jane (University of Central Florida)
D. J. Rasmussen (Princeton University)
Marjolijn Haasnoot (Deltares, Universiteit Utrecht)
Gregory G. Garner (GRO Intelligence)
Robert E. Kopp (Rutgers University)
Michael Oppenheimer (Princeton University)
Aimée B.A. Slangen (NIOZ Royal Netherlands Institute for Sea Research)
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Abstract
Sea-level rise amplifies the frequency of extreme sea levels by raising their baseline height. Amplifications are often projected for arbitrary future years and benchmark frequencies. Consequently, such projections do not indicate when flood risk thresholds may be crossed given the current degree of local coastal protection. To better support adaptation planning and comparative vulnerability analyses, we project the timing of the frequency amplification of extreme sea levels relative to estimated local flood protection standards, using sea-level rise projections of IPCC AR6 until 2150. Our central estimates indicate that those degrees of protection will be exceeded ten times as frequently within the next 30 years (the lead time that large adaptation measures may take) at 26% and 32% of the tide gauges considered, and annually at 4% and 8%, for a low- and high-emissions scenario, respectively. Adaptation planners may use our framework to assess the available lead time and useful lifetime of protective infrastructure.