On 15 November 2024, a widespread coastal flooding event swept across China’s coastal zones, bringing into sharp focus the urgency of characterizing flood risks driven by tidal dynamics. To date, however, tide-driven flooding of this nature has received scarce research attention along the entirety of China’s coastline. Against this background, the present work seeks to raise the profile of high-tide flooding (HTF) across China’s coastal regions by quantifying the future potential for recurrent HTF events. Drawing on a likelihood-derived proxy for HTF inundation thresholds and numerically modeled water levels, we assess the joint influence of sea level rise (SLR) and amplified astronomical tides on projected increases in HTF exceedance frequency.
Our analysis reveals a marked uptick in HTF exceedance frequency in the decades ahead, driven by both SLR and the upward phase of the nodal tidal cycle. Under the Shared Socioeconomic Pathway 2-4.5 (SSP2-4.5) scenario in particular, HTF exceedance events are forecast to occur at an average rate of twice per week along China’s northern coastline by the 2050s — a frequency far exceeding that projected for the southern coast. Chronic HTF exceedance conditions are set to emerge first in Bohai Bay under the SSP2-4.5 scenario, with onset expected by the mid-2040s. We further demonstrate that projected tidal amplification will not only boost the annual count of HTF exceedance days but also advance the timing of chronic HTF onset. Taken together, our findings underscore the substantial projected increase in HTF occurrence potential along China’s coastline, and call for heightened research and policy attention to HTF hazards in this region.

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