Changing Vertical Datums
Datums are baseline standards against which we measure geographic location and elevations. They are frequently referenced in state and local codes to ensure a precise, shared understanding of regulatory action. NOAA is updating their geodetic datums (anticipated 2024-2025), which include horizontal (NAD 83) and vertical (NAVD 88) datums, and their tidal datums (anticipated 2026), which impact definitions of water levels (e.g. mean lower low water, mean low water, mean sea level, mean high water, etc.). The code of Virginia uses tidal datums as the baseline for legal (e.g. waterfront property) boundaries, ecological (e.g. tidal wetlands) boundaries, and to constrain jurisdictional roles (e.g. Potomac River Fisheries Commission). Derived elevation measurements (such as freeboard standards) are also used in local codes. Although less frequently used, the geodetic datum has also been referenced in bills for defining legal boundaries (e.g. public oyster grounds). NOAA recognizes the potential ramifications of the changing baseline resulting from the updated datums and recommends evaluating if a state needs to change its legislation as a result and if it is necessary to create a plan to ensure that state datasets are either: 1) adapted to the new datums by conversion to the new datums or 2) by being clearly identified with datum under which they were developed and then including/referencing the appropriate conversion methodology to shift uses of old datums to the new ones. This project will catalog references to vertical datums in the Virginia Code, Virginia Administrative Code, and at least one set of representative local government documents, evaluate potential impacts, evaluate how this might affect policy, and make recommendations to address latent policy changes if necessary.
- Peoples and Entities Involved Outside of W&M:
- Outside reviewers and sample local government TBD
- Cirse Gonzalez, Coastal Training Program Coordinator, Chesapeake Bay National Estuarine Research Reserve-VA
- Erin Reilly, Conservation and Restoration Coordinator, Chesapeake Bay National Estuarine Research Reserve-VA
- People and Entities at W&M Involved:
- Molly Mitchell, Asst. Professor, Center for Coastal Resource Management
- Jeryl Phillips, Research Scientist, Center for Coastal Resources Management
- Thomas Ruppert, VCRC Director
- Cameron Bruce, VCRC Assistant Director
- Kevin Fontenot, W&M Law School J.D. Candidate (Summer, 2025)
- Natalie Klesch, VIMS M.A. in Marine Policy Candidate (Summer, 2025)
This Vertical Datums Project is funded by the Virginia Coastal Zone Management Program through a grant to DEQ from NOAA under the Federal Coastal Zone Management Act.
