[Federal Register Volume 68, Number 102 (Wednesday, May 28, 2003)]
[Notices]
[Page 31689]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-13190]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration


Notice of Change to the Nation's Tidal Datums With the Adoption 
of a New National Tidal Datum Epoch Period of 1983 through 2001

AGENCY: National Ocean Service (NOS), National Oceanic and Atmospheric 
Administration (NOAA), Department of Commerce (DOC).

ACTION: Notice to advise the public of national updates to tidal datums 
due to the adoption of a new National Tidal Datum Epoch 1983 through 
2001.

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SUMMARY: NOAA's National Ocean Service, Center for Operational 
Oceanographic Products and Services (CO-OPS), will update the Nation's 
tidal datums to a new National Tidal Datum Epoch (NTDE) to adjust for 
changes in mean sea level that have occurred along the Nation's coast 
over the past 25 years. The NTDE update from the 1960-1978 to the 1983-
2001 time period will be effective April 21, 2003. The NTDE is a 
specific 19-year period over which tide observations are taken to 
determine Mean Sea Level and other tidal datums such as Mean Lower Low 
Water and Mean High Water. This period includes an 18.6 year 
astronomical cycle that accounts for all significant variations in the 
distances to the moon and sun that cause slowly varying changes in the 
range of tide. It is the policy of NOS to consider a revised NTDE every 
20-25 years in order to take into account relative sea level changes 
caused by global sea level rise and the effects of long term land 
movement on local sea level due to subsidence or glacial rebound. The 
NTDE of 1983-2001 has been adopted so that all tidal datums throughout 
the United States will be based on one specific common reference 
period.
    This action is necessary to provide the latest up-to-date 
information available for applications that are essential to supporting 
Federal, State and private sector coastal zone activities, including 
hydrographic surveys and coastal mapping, navigational safety, wetland 
restoration, marine boundary determinations, coastal engineering, storm 
warnings and hazard mitigation, emergency management, and hydrodynamic 
modeling.

FOR FURTHER INFORMATION: Visit the NOS' CO-OPS Web site (http://www.tidesandcurrents.noaa.gov) or contact the CO-OPS office at the 
following address: NOAA, National Ocean Service, CO-OPS, Products and 
Services N/OPS3, Attn: Water Levels, 1305 East-West Highway, Silver 
Spring, MD 20910-32821, U.S.A., Telephone: 301-713-2877 x176, Fax: 301-
713-4437.

SUPPLEMENTARY INFORMATION: Due to the small vertical changes (0.10 
meters/0.3 foot or less) in comparison to the overall accuracy of 
hydrographic-cartographic processes and scale of the charts, for the 
most part, the shoreline, depth soundings values, isobaths, etc., will 
not be significantly modified as a result of the tidal datum updates. 
However, in some regions that have experienced rapid land movement, 
changes to actual soundings and shoreline depiction may be required on 
the next regularly scheduled chart edition. Although depictions of the 
datum changes will not be evident on the largest scale NOS nautical 
charts, the datum changes will be noticeable when establishing or re-
occupying tide stations using accepted surveying techniques and the 
numerical relationships for tidal benchmarks provided by NOS' CO-OPS. 
These tidal datum relationships will be made available to the public in 
the form of updated published tidal benchmark sheets and accepted 
datums.

    Dated: May 21, 2003.
Jamison S. Hawkins,
Acting Assistant Administrator, Ocean Services and Coastal Zone 
Management, National Oceanic and Atmospheric Administration.
[FR Doc. 03-13190 Filed 5-27-03; 8:45 am]
BILLING CODE 3510-JE-M