Teton County, WY Environmental Rules: Flood Zones (2026)

Floodplain regulation in unincorporated Teton County is governed by the Teton County Floodplain Management Resolution, adopted under the authority of Wyoming Statute 18-5-201 and administered by the County Engineer as designated Floodplain Administrator (Section 1310). The current resolution was originally approved August 19, 2010 and amended September 15, 2015. Areas of Special Flood Hazard are based on the Flood Insurance Study for Teton County and Incorporated Areas dated September 16, 2015 with accompanying Flood Insurance Rate Maps (Section 1220). The countywide DFIRM consists of 78 panels (panel suffixes C1525E through C3300E) maintained at the FEMA Map Service Center and on file at the County Engineering Building, 320 S. King Street, Jackson. Mapped flood zones include Zone A, AE, AH, AO, AI-99, V, and VO along the Snake River, Flat Creek, Fish Creek, and the Gros Ventre River. Wyoming participates as a state-coordinated NFIP program through the Wyoming Office of Homeland Security (state coordinator Aaron Birkemeier, 307-777-4910). Under Section 1420.A, new construction and substantial improvement of any residential structure must have the lowest floor (including basement) elevated one (1) foot above the base flood elevation, exceeding the FEMA NFIP minimum. Below-grade crawlspaces are permitted only when they meet seven specific conditions including interior grade no lower than 2 feet below lowest adjacent grade, crawlspace height not exceeding 4 feet, adequate drainage, anchoring against flotation, flood-resistant materials, and automatic hydrostatic equalization openings. Nonresidential structures (Section 1420.B) may either elevate one foot above BFE or be dry-floodproofed with watertight walls and registered engineer/architect certification. Manufactured homes (Section 1420.D) must be installed on a permanent foundation elevated to or above BFE in new parks/expansions or where the home suffered substantial damage; existing-park placements must elevate one foot above BFE or be supported on reinforced piers at least 36 inches above grade. Recreational vehicles (Section 1420.E) may stay in an SFHA fewer than 180 consecutive days, otherwise must be fully licensed and ready for highway use or meet manufactured-home elevation and anchoring standards. Section 1450 prohibits all encroachments (fill, new construction, substantial improvement, or other development) within the regulatory floodway unless a registered engineer demonstrates through hydrologic and hydraulic analysis that there will be no increase in base flood elevation; CLOMR/floodway revision through FEMA is required for any approved encroachment that would raise BFE. A Development Permit is required before any construction, mining, dredging, filling, grading, paving, excavation, drilling, or storage of equipment or materials in an SFHA (Sections 1230 and 1330). Substantial improvement and substantial damage are defined at 50% of pre-improvement market value (Division 1100). The county also coordinates with the U.S. Army Corps of Engineers Walla Walla District on the federally constructed Snake River and Gros Ventre Levee System (24.5 miles), with annual July inspections and fall rehabilitation work. As of recent FEMA correspondence, three active Letter of Map Revision cases are pending or recently approved: Snake River (Case 23-08-0788P), Rafter J Ranch Flat Creek (Case 23-08-0662P), and Flat Creek G&F Stream Restoration Project (Case 23-08-0655P). Permit applications are processed through the SmartGov platform; questions go to the Floodplain Administrator at (307) 733-3317.