Impact assessment of sea level rise-induced high tide flooding and socioeconomic losses in a highly vulnerable coastal region

Study region: The southwestern coast of Taiwan. Study focus: By employing sea-level rise (SLR) projections from the Sixth Assessment Report, we assess the future high tide flooding (HTF) and the resulting inundation extents and evaluate the impacts on populations and economic losses. New hydrological insights for the region: Under the low-emissions scenario, SLR-induced minor HTF days, i.e., 0.55 m above the mean higher high water (MHHW) are projected to exceed 300 annually by 2100; moderate HTF (0.85 m above the MHHW) events are expected to occur daily in the high-emissions scenario by 2090; major HTF (1.2 m above the MHHW) events were projected to occur in 2070, regardless of the emission scenario considered; regarding the extent of inundation, the projected HTF events would lead to a flooded area ranging from 30 to 600 km2. The impact on the present population ranged from 41,000 to 490,000 individuals. The upper limit of total economic losses based on current land use resulting from HTF was anticipated to range from 3.25 million US dollars to 35.31 million US dollars across the low-, medium-, and high-emission scenarios. The at-risk population decreased from 520,000 in 2008–490,000 in 2022, representing a decline of 5.8 % over 15 years in this coastal region.