Extreme sea levels threaten Department of Defense (DoD) facilities, operations, and connected communities. To support informed decision making and resilient planning, the DoD Regional Sea Level (DRSL) database provides regionalized sea level change scenarios for three future time horizons to assess vulnerability and risks at DoD sites worldwide. With the recent release of more detailed projections of extreme water levels, and with the development of advanced methods for defining extreme water level (EWL) probabilities, the modeling and analysis study will result in recommendations for DRSL updates and expansions for consideration by the Coastal Assessment Regional Scenario Working Group. Two methods for projecting EWL using the TESLA model (Marra et al. 2022) and global models of storm surge and waves forced by global model outputs, will be compared at four total test sites, two in the Atlantic and two in the Pacific, for the purpose of improving extreme event assessments. Tools to incorporate wave effects in extreme sea levels will be demonstrated at the test sites. Mean sea level projections at sites that can be added to the Real Property Asset Database and a methodology for updating vertical land motion (VLM) rates will be developed.

A formalism for selecting VLM rates, a key contributor to regional sea level variations, will be specified using tide gauge, satellite altimetry, and global positioning system data as well as glacial isostatic adjustment models. The DRSL incorporates a regional frequency analysis (RFA) for specifying EWL statistics from nearby tide gauges. Recent updates to the RFA methodology (Sweet et al. 2020, Sweet et al. 2022) will be evaluated for possible incorporation into the DRSL. Other approaches for specifying EWLs (e.g., Anderson et al. 2019, Muis et al. 2020) will be evaluated and best estimates will be developed. A demonstration of a Total Water Level (TWL) product (combined sea level, tides, water level residuals, and wave runup) (Erikson et al. 2018, Anderson et al. 2021) will be implemented at selected sites with recommendations for potential TWL products.

The information will support resilient strategies for facilities management, emergency planning, and regional operations.

(Anticipated Project Completion-2026)