Sea Level Rise Allowance Calculator for a Cape Coral Seawall Cap

This sea level rise allowance calculator is for the cap of a Cape Coral seawall. You enter the cap height, the number of years you want to plan for and, if you like, a start year. It adds up the rise NOAA's three middle scenarios put between those two years and shows what that does to the gap between your cap and two water levels. We are an independent referral service that connects visitors with independent local contractors, not a contractor or an engineer.

En español: Calculadora de aumento del nivel del mar para la tapa de un muro (Cape Coral)

How the math works

1. Pick the years.

   End year = start year + years of service, capped at 2100, the last year NOAA gives a table for.

2. Find the rise at each year.

   NOAA gives the rise since 2000 at 2050 and 2100 for each scenario. We draw a straight line from 2000 to 2050 and from 2050 to 2100 and read the rise at your two years.

3. Subtract.

   Rise at the end year minus rise at the start year is the extra rise your wall may face. We convert meters to feet (1 m = 3.28084 ft).

4. Move the water levels up.

   Gap to the average high tide = cap - 0.28 ft - added rise. Gap to the minor flood level = cap - 1.97 ft - added rise. Both levels are on our NOAA sea level page.

Table: NOAA's rise for the Eastern Gulf, since the year 2000

Median values from NOAA's 2022 technical report, converted from meters to feet (our arithmetic). The tool uses these three rows. NOAA also gives a Low and a High scenario that we leave out so the tool stays simple; the High scenario ends 2100 at 2.2 m (7.2 ft).

Example with round numbers

A cap at 3.6 ft NAVD88, planned for 30 years from 2026 (so to 2056). Before the added rise, the cap sits 3.32 ft above average high tide and 1.63 ft above the minor flood level.

Columns are NOAA's Intermediate-Low, Intermediate and Intermediate-High scenarios.

What the result leaves out

• Your canal. The scenarios are regional. A canal can rise and fall differently from the river or the Gulf.
• Land movement and local effects. NOAA's regional values include average land movement, not a survey of your lot.
• Storm surge and waves. A hurricane puts water far above these levels for hours. The scenario rise comes on top of any surge.
• Rise before your start year. The two levels used here come from a 1983 to 2001 reference period. Water already sits higher today, and the tool only adds the future rise from your start year.
• Everything about the wall itself. Panels, depth, tiebacks and the cap design are the engineer's job.

Questions to ask your engineer before you pick a cap height

• Which service life does the design assume? Ask for the number of years in writing.
• Did the design allow for future sea level rise? Ask which scenario or source, and who chose it.
• What cap elevation is on the plans? Ask for it in feet NAVD88 and ask what it was measured against.
• Can the cap be raised later? Some designs make it easier to add height than others. Ask.
• Does a higher cap change anything next door? See returns and neighbor tie-ins.

Compare written bids with the seawall bid comparison calculator, and read how to choose a seawall contractor before you sign.

Next step: get real quotes

This result is a planning check, not a quote or a design. Use the request form on this page to be connected with independent local marine contractors. We are a referral service, not a contractor. Ask each one which cap height the plans use and why.

Sources

• Global and Regional Sea Level Rise Scenarios for the United States (NOAA Technical Report NOS 01, 2022): Table 2.2 gives 2050 values by region and Table 2.5 gives 2100 values, in meters, relative to the year 2000. The Eastern Gulf is the west coast of Florida to Mississippi.
• Cape Coral Sea Level and High Tides: NOAA Gauge Data on this site, for average high tide (+0.28 ft NAVD88) and the minor flood level (+1.97 ft NAVD88) at NOAA's Fort Myers gauge, station 8725520.