Martin County, FL Environmental Rules: Flood Zones (2026)

Division 10 reaches nearly everything built or changed in a flood hazard area: subdivisions, fill and grading, utility installations, new or altered buildings, manufactured homes, tanks, recreational vehicles, swimming pools and emergency generators. Section 4.422.C adopts the Flood Insurance Study dated February 19, 2020 and the accompanying Flood Insurance Rate Maps, with all later amendments, as the minimum basis for the mapped areas. The studies and maps are on file in the Engineering Department. Where this division conflicts with another regulation, the more restrictive one governs (section 4.422.E), and the county engineer holds the Floodplain Administrator post unless the County Administrator decides otherwise (section 4.424.A).

Permits come in two forms. Ordinary development needs a development order, building permit or Excavation and Fill Permit, and none is issued until the division is satisfied. Development in a Special Flood Hazard Area that sits outside the Florida Building Code needs a separate Floodplain Approval under section 4.425. That list covers railroads, nonresidential farm buildings, temporary construction sheds, mobile or modular temporary offices, electric utility generation and distribution facilities, chickees, family mausoleums up to 250 square feet, and temporary film production structures. Applicants are encouraged to meet the Floodplain Administrator before filing.

Construction standards are specific. Accessory structures below base flood elevation can hold only parking or storage. In Zone A/AE they are limited to one story and 600 square feet with flood openings; in Zone V/VE and Coastal A Zones they cannot sit below elevated buildings and are capped at 100 square feet. Materials below base flood elevation plus one foot must resist flood damage, and mechanical, plumbing and electrical systems go at or above that same level. No new manufactured home can be installed in Zone V or a Coastal A Zone. In a regulatory floodway, no fill, regrading or other development is authorized unless the encroachment analysis shows no increase in the base flood elevation.

Substantial improvement is a 50 percent test. Repairs, additions and rehabilitation within a five-year period that cost 50 percent or more of the building's market value before the work starts qualify, and so do repairs after substantial damage of the same size. For each building, the five-year clock begins with its first improvement after March 16, 2015.