The Seawall That Is Not the Water Boundary
Lot 4, Block A, Sunset Isle, is a Gulf-front parcel. The 1972 deed bounds it on the west by "the mean high water line of the Gulf of Mexico"; the east line is 100.00 ft from the east right-of-way of Gulf Boulevard. A 1974 survey shows a steel seawall at the west line and a MHW line 6 ft west of that seawall. Today the beach has accreted: your level/tide observations place MHW 28 ft west of the seawall. The owner wants the survey to stop at the seawall because "that is the developed line" and because the lender's flood certificate uses the seawall. The adjacent owner says the accretion belongs to the state. You also find a 2019 survey by another firm showing MHW 19 ft west of the seawall, based on a single day's water-level reading with no tide study. The owner asks you to adopt the 2019 line because it is "more conservative."
1. What is the legal boundary of the lot, and what is the surveyor's role in locating it?
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The deed boundary is the mean high water line, not the seawall. The seawall is a man-made occupation feature and may be evidence of where the shoreline was in 1974, but it does not replace the called water boundary. The surveyor's role is to locate and monument the MHW line as a boundary of the upland, not to decide title to accretion or submerged land. Under Florida law, the state holds title to sovereign submerged lands below the MHW line, while accretion may belong to the upland owner under common-law rules; those title questions are ultimately for the courts or the state, not for the surveyor's certificate. Show the seawall, the 1974 MHW line, the current MHW line, and any prior survey line, and explain what each represents. Do not stop the survey at the seawall merely because the lender's flood certificate uses it.
2. How should you determine the mean high water line, and why is the 2019 single-day line unreliable?
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MHW is a tidal datum, defined as the average of high waters over the National Tidal Datum Epoch, not the water level on one day. Use a defensible method: observe tides over a sufficient period with a staff or gauge, reduce the observations to a local tidal datum, and transfer the MHW elevation to the shore profile. Published tide-station data, leveling from a known datum, and repeated profiles help. A single-day reading can be affected by wind, barometric pressure, seasonal setup, and wave run-up, so it may be several feet off. The 2019 line may be useful as a comparison, but it is not controlling unless the method is documented and reduced to MHW. Your survey should state the method, the tide observations, the datum, and the date. If the owner wants a 'conservative' line, explain that choosing a line for its effect on the lender or the neighbor is not a boundary determination.
3. What should you show on the survey and what should you tell the owner and the adjacent owner?
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Show the current MHW line as a surveyed boundary line, the seawall as a separate feature with ties, the 1974 MHW line from the prior survey, and the 2019 line as a prior survey line if you can verify its basis. Add notes explaining that the seawall is not the deed boundary and that the area between the seawall and MHW is shown for information. Tell the owner that the survey cannot be shortened to the seawall to satisfy a flood certificate; the lender can use the survey as it is. Tell the adjacent owner that you are locating the MHW line, not adjudicating ownership of accretion. If the owners dispute title, recommend that they consult counsel and consider a boundary agreement or quiet-title action. Your file should document the tide data and the reason for rejecting the single-day line so your judgment is defensible if challenged.