Lake Martin seawall elevations: read the right reference.
Keep full-pool elevation, exposed wall height and the top-of-cap survey measurement separate before changing your shoreline.
- Top of the capMeasured from a fixed survey reference.
- WaterlineChanges with weather and reservoir operations.
- Survey reference (datum)A named reference, such as NAVD88.
Use the survey reference printed beside the elevation.
491 MSL and 490 Martin Datum are not wall-height targets.
Alabama Power’s residential guidelines describe Lake Martin full pool as 491 feet MSL, also expressed as 490 feet Martin Datum. Those are the document’s reservoir references. They do not prescribe the top of your seawall.
Do not convert a NAVD88 survey by simply adding or subtracting one foot. Ask the surveyor to establish the relationship between the references used on your property documents and the shoreline approval.
Bring the survey and approved shoreline drawing.
Show the proposed cap elevation, existing grade, dock landing and drainage outlets on the project drawing. Ask the designer which changes the existing structure can support and how runoff will leave the retained land.
The control strip, where applicable, is described from a specified contour—not today’s waterline. Confirm Alabama Power’s rights and the applicable local floodplain review for the parcel.
Martin, Yates & Thurlow residential guidelines · Elmore County floodplain and access FAQ
How high should your seawall be?
Begin with the approved shoreline plan, survey and proposed change. Ask Alabama Power and the local reviewer which elevation constraints apply. The designer also needs to resolve drainage, retained ground and connections to adjoining structures.
Use the surveyed top-of-cap elevation and its named reference. Exposed wall height changes with Lake Martin’s water level; the survey value describes the cap against a fixed reference. Those measurements cannot be substituted for one another.
Find these two items on your survey.
Locate both the cap value and its datum on the survey. The following number is a hypothetical reading, not a Lake Martin construction requirement.
Seawall cap elevation
- Top of seawall cap
- 493.00 ft
- Survey reference (datum)
- NAVD88
493.00 ft NAVD88 is shown only to demonstrate the notation. It is not a recommended cap elevation.
Match the value and the reference.
- The elevation: use the number for the top of the wall cap, not a building floor, water depth or the wall’s full height.
- The reference: copy the name beside the elevation, such as NAVD88 or NGVD29. You can compare elevations only when they use the same reference.
- Cannot find both? Choose “No / not sure” in the checker. Ask a surveyor to help find them; measuring from the water will give a different result.
What does NAVD88 mean?
A datum defines the reference for an elevation. NAVD88, NGVD29 and the reservoir reference named in a shoreline document must not be treated as interchangeable labels. Have the surveyor resolve any conversion needed for this property. Read NOAA’s explanation of survey references.
A building elevation certificate may not contain a seawall cap measurement. If the shoreline value or reference is absent, request the appropriate survey information. Measuring upward from the visible waterline does not supply a fixed datum.
Repair, replacement and permits
Adding height changes the structure and the way the land meets the wall. Ask the designer to evaluate retained loads, existing support, runoff and dock or stair connections. Submit the actual proposed change rather than describing a height increase as routine surface repair.
Use the permit guide to find the local, ADEM and U.S. Army Corps of Engineers contacts. Describe your location and planned work and ask which permits you need. Alabama Power’s application instructions explain the information needed for shoreline projects.
Common questions
How do I plan a change in wall height?
Give the designer the existing survey and a marked description of the proposed change. Resolve the supports, drainage and adjacent structures, then confirm the permission needed for that scope.
Is maximum height the height I must build?
A stated upper limit does not choose a design elevation. Confirm any applicable lower limit and have the designer resolve the property’s structural, drainage and access needs.
What if I do not know the elevation?
You can start with the property address and what you want to change. A surveyor can identify the top-of-cap elevation and its reference on your survey.
Can an existing seawall be raised?
An engineer needs to check the wall, supports and drainage before recommending a height change. The right approach may involve modifying the wall or replacing parts of it.
Does meeting a number mean the wall is safe?
Height is only one part of the wall’s condition. The supports, drainage and signs of damage also matter. Use the warning-sign check to prepare for an assessment.
How can I get help with the height?
Tell us the property’s city or county and what you want to change. Discuss the next steps, including whether you need a survey or seawall assessment. Confirm any service details and price before going ahead.
Show sourcesHide sources
- Martin, Yates & Thurlow residential guidelinesSource reviewed 2026-11-04 · official indexed text
- Elmore County floodplain and access FAQSource reviewed 2026-11-04 · official indexed text
Ask about local requirements
Identify the property and the question to resolve. Keep any available survey with your planning notes.