Union, NY Hurricane Preparedness: Flood Elevation (2026)

Section 121-14, Specific standards, applies in all areas of special flood hazard where base flood elevation data has been provided under § 121-6 or obtained by the local administrator under § 121-12(B). It is the part of Chapter 121 that turns a flood map into construction requirements for storm and high-water events.

For residential construction, subsection A(1) requires new construction and subsequent improvements to have the lowest floor, including basement or cellar, elevated to two feet above the base flood elevation. Enclosed areas below the lowest floor must equalize hydrostatic flood forces on exterior walls by letting floodwaters enter and exit automatically. The design either carries a licensed professional engineer's or architect's certification or meets minimum criteria: at least two openings, a total net area of not less than one square inch for every square foot of enclosed area subject to flooding, with the bottom of every opening no higher than one foot above the lowest adjacent finished grade. Louvers, valves, screens or other coverings are allowed if they permit the automatic entry and exit of floodwaters.

For nonresidential construction, subsection B lets the owner choose: elevate the lowest floor, including basement or cellar, to or above the base flood elevation, or floodproof to the base flood level. An elevated building uses the same automatic openings rule. A floodproofed building needs a licensed professional engineer or architect to certify the design makes the structure watertight with walls substantially impermeable to water and components able to resist hydrostatic and hydrodynamic loads and buoyancy. A licensed professional engineer or land surveyor certifies the specific floodproofed elevation above mean sea level, and the local administrator keeps a copy of every certificate on record.

Where no base flood elevation exists, subsection C requires the lowest floor, including basement, to be elevated at least two feet above the highest adjacent grade next to the foundation, with the same automatic openings rule.

Related general standards in § 121-13 require anchoring against flotation, collapse and lateral movement, and say manufactured home anchoring is in addition to state and local anchoring requirements for resisting wind forces. Electrical, heating, ventilation, plumbing and air-conditioning equipment must be designed or located to keep water out, and equipment placed below the base flood elevation needs an engineer's or architect's certification. Section 121-9 warns that larger floods can and will occur on rare occasions.