The highest annual tide line is the jurisdictional limit for all coastal wetlands and is used by local, state, and federal authorities in determining setbacks or impact to the natural resource. The highest annual tide typically occurs several times a year and corresponds to the full moon. Highest annual tide is not the average high tide that occurs twice each day.
The highest annual tide elevation can be determined by professionals; however, in lieu of hiring a professional there is a simple method for locating highest annual tide that can be performed by property owners with a few simple tools (NOAA Annual Tide Table, grade stake, string, and a line level).
1) Obtain the annual tide table for your area from the NOAA website. The pdf annual tide table format provides a good snapshot of the predicted tidal elevation for a 12-month period.
2) Obtain the time and elevation of today’s high tide as well as the highest elevation listed for the 12-month period from the tide table. For example, today’s high tide might be at 2:14 pm and be a 9.2-foot tide, while the highest tide listed might be a 12.1-foot tide.
3) At the exact time of today’s high tide place the stake at the location of the high tide.
4) Measure up the stake the difference between today’s tide elevation and the highest one listed in the tide table and mark the location on the stake.
5) Tie the string to the mark on the stake and with the line level attached, pull the string back toward land (away from the water) until the level string intersects the beach or bluff profile. Mark this location as it represents the highest annual tide elevation. Since tidal elevations are not typically straight lines, repeat this exercise at several locations across the frontage to accurately locate the highest annual tide line.