Disruptive Role of Vertical Land Motion in Future Assessments of Climate Change-Driven Sea-Level Rise and Coastal Flooding Hazards in the Chesapeake Bay

Future projections of sea-level rise (SLR) used to assess coastal flooding hazards and exposure throughout the 21st century and devise risk mitigation efforts often lack an accurate estimate of coastal vertical land motion (VLM) rate, driven by anthropogenic or non-climate factors in addition to climatic factors. The Chesapeake Bay (CB) region of the United States is experiencing one of the fastest rates of relative sea-level rise on the Atlantic coast of the United States. This study uses a combination of space-borne Interferometric Synthetic Aperture Radar (InSAR), Global Navigation Satellite System (GNSS), Light Detecting and Ranging (LiDAR) data sets, available National Oceanic and Atmospheric Administration (NOAA) long-term tide gauge data, and SLR projections from the Intergovernmental Panel on Climate Change (IPCC), AR6 WG1 to quantify the regional rate of relative SLR and future flooding hazards for the years 2030, 2050, and 2100. By the year 2100, the total inundated areas from SLR and subsidence are projected to be 454(316-549)-600(535-690) km(2) for Shared Socioeconomic Pathways (SSPs) 1-1.9 to 5-8.5, respectively, and 342(132-552)-627(526-735).... km(2) only from SLR. The effect of storm surges based on Hurricane Isabel can increase the inundated area to 849(832-867)-1,117(1,054-1,205) km(2) under different VLM and SLR scenarios. We suggest that accurate estimates of VLM rate, such as those obtained here, are essential to revise IPCC projections and obtain accurate maps of coastal flooding and inundation hazards. The results provided here inform policymakers when assessing hazards associated with global climate changes and local factors in CB, required for developing risk management and disaster resilience plans. Plain Language Summary The Chesapeake Bay (CB) region of the United States is experiencing one of the fastest rates of relative sea-level rise on the Atlantic coast of the United States. However, future projections of sea-level rise (SLR) used to assess coastal flooding hazards and exposure throughout the 21st century often lack an accurate estimate of changes in land elevation. This poses a significant challenge to present and future management efforts because vertical land motion (VLM) can cause underestimation/ overestimation of flooding risk to coastal communities. This work combines satellite data and in situ observations to measure VLM and assess 21st-century flooding hazards due to SLR, hurricane effect, and land elevation change in the CB. By the year 2100, the total inundated areas from SLR and subsidence are projected to be 454-600 km(2) for very low to very high greenhouse gas scenarios. The effect of storm surges associated with Hurricane Isabel can increase the inundated area to 849-1,117 km(2) under different SLR scenarios and VLM. The results provided here inform policymakers when assessing hazards associated with global climate changes and local factors.