Seawalls in Islamorada

Bay side and ocean side tides differ fourfold

NOAA's Florida Bay gauge at Upper Matecumbe Key shows a great diurnal range of only 0.61 ft, with mean higher high water about 0.41 ft below NAVD 88, while the Hawk Channel gauge a short way across the key shows 2.28 ft (1983 to 2001 epoch). A lift or floating dock sized for one side of Islamorada is wrong for the other.

The tide also sets how much of the wall can be worked on dry at low water, which changes crew time.[1][2]

Flood maps from 2005, new ones pending

Islamorada still builds to effective flood maps dated 18 February 2005. Preliminary maps went through appeals between March and June 2021, FEMA has not announced when they take effect, and the Village has promised six months' notice once it does.

Height is the first question on any wall job here, because it decides whether a repair can stay at the current cap or turns into a raise.[3]

Watch the datum: about 1.5 ft

The Village notes that converting from NGVD29 to NAVD88 shifts elevations by about -1.5 ft on average in Monroe County, and the shift varies from place to place. Old plans and new maps use different datums, so a cap or floor height has to be converted before anyone compares numbers.[3]

Seawalls and riprap inside the setback

Islamorada's shoreline setback keeps buildings 20 to 50 ft from mean high water, but it does not apply to seawalls, riprap and bulkheads whose purpose is erosion control or upland protection. Because the Keys are an area of critical state concern, the 2024 ordinance was approved by the Florida Department of Commerce.

We build that permit path into the schedule from the first site visit.[4]

What makes Islamorada different

Principal buildings sit 20 ft from the mean high water line on altered shorelines such as canals, 30 ft on open water with conditions, and 50 ft on unaltered shorelines. Docks, lifts, davits, seawalls and riprap are water-dependent structures that may sit inside that setback under the Village's standards.[4]

Sanctuary and manatee layers

The federal small-project permit, SPGP VI, required Sanctuary sign-off before any Islamorada project in Keys waters, and crews follow the state manatee conditions on every in-water job.[5][6]

Permits for seawalls in Islamorada

• Islamorada, Village of Islands, Planning and Development Services: Docks, lifts and shoreline structures under Village Code Chapter 30.
• Florida Keys National Marine Sanctuary: Sanctuary waters surround every Islamorada key from the mean high water mark; we confirm what Sanctuary approval each project needs.
• Florida DEP or South Florida Water Management District: State permit or exemption; part of the Village's water is the Lignumvitae Key Aquatic Preserve.
• US Army Corps of Engineers, Jacksonville District: Federal authorisation for work in the Sanctuary waters around the Village.

Which permits does seawall work need?

In Miami-Dade, any work in, on, over or upon tidal waters needs a DERM Class I permit under Section 24-48 of the County Code, including inside cities. Minor repairs are exempt, cap and tieback work gets an expedited authorisation, and rebuilding a wall at the mean high water line or up to 18 inches waterward is a short-form permit approved by staff.

The city building department also issues a structural permit. A state exemption does not remove county and city permits: Florida Statute 403.813 says its exemptions do not relieve anyone from county and municipal requirements, so in Miami-Dade a DERM Class I permit still applies.[7][8]

How long does a seawall last?

Fort Lauderdale's seawall ordinance FAQ assumed a design life of about 50 years, and city engineers described a 30 to 50 year lifespan for a wall built today. Salt water, wave action from boat wakes and rising tides shorten that when cracks and failed joints are left open.[10]

Why heights matter now

Cities are raising the bar. Miami Beach requires new and substantially repaired seawalls to reach 5.7 ft NAVD, Coral Gables sets bulkheads at a minimum of 6 ft NGVD 1929, and Fort Lauderdale requires 5 ft NAVD. A repair that triggers these rules can turn into a raising job, so we check the local standard before we price.[9][12][13]

Frequently asked questions