Doubling of coastal flooding frequency within decades due to sea-level rise

TLDR

Global climate change drives sea‑level rise, which, though smaller than natural tidal and storm‑surge fluctuations, can rapidly increase the frequency and severity of coastal flooding, and current global estimates underestimate this impact by neglecting wave‑induced water‑level elevations. The study aims to estimate global increases in coastal flooding by combining sea‑level projections with wave, tide, and storm‑surge models using extreme‑value theory. Using extreme‑value theory, the authors integrated sea‑level projections with wave, tide, and storm‑surge models to produce continuous global estimates of flooding frequency. They found that tropical regions with short‑tailed flood‑level distributions will experience the largest increases, with a 10–20 cm sea‑level rise by 2050 more than doubling extreme water‑level events, threatening developing economies and low‑lying Pacific islands.

Abstract

Abstract Global climate change drives sea-level rise, increasing the frequency of coastal flooding. In most coastal regions, the amount of sea-level rise occurring over years to decades is significantly smaller than normal ocean-level fluctuations caused by tides, waves, and storm surge. However, even gradual sea-level rise can rapidly increase the frequency and severity of coastal flooding. So far, global-scale estimates of increased coastal flooding due to sea-level rise have not considered elevated water levels due to waves, and thus underestimate the potential impact. Here we use extreme value theory to combine sea-level projections with wave, tide, and storm surge models to estimate increases in coastal flooding on a continuous global scale. We find that regions with limited water-level variability, i.e., short-tailed flood-level distributions, located mainly in the Tropics, will experience the largest increases in flooding frequency. The 10 to 20 cm of sea-level rise expected no later than 2050 will more than double the frequency of extreme water-level events in the Tropics, impairing the developing economies of equatorial coastal cities and the habitability of low-lying Pacific island nations.