Grant County, WI Environmental Rules: Flood Elevation Requirements (2026)

Grant County builds its elevation standard on the regional flood elevation plus freeboard. Section 290-46 defines the FLOOD PROTECTION ELEVATION as an elevation of two feet of freeboard above the water surface profile elevation designated for the regional flood. Freeboard is a safety factor above a calculated flood level that compensates for ice jams, debris accumulation, wave action, obstruction of bridge openings and floodways, and loss of flood storage areas. The regional flood is the flood with a one-percent chance of being equaled or exceeded in any given year, and on the FIRM the regional flood elevation is equivalent to the base flood elevation.

Flood-fringe standards (§ 290-27). A residence newly built or moved into the flood-fringe, including a manufactured home, must have its lowest floor at or above the flood protection elevation on fill. The fill must be one foot or more above the regional flood elevation and extend at least 15 feet beyond the limits of the structure. A basement or crawlway floor can sit at the regional flood elevation only if it is dry floodproofed to the flood protection elevation, and none is allowed below the regional flood elevation. Accessory structures go on fill with the lowest floor at or above the regional flood elevation; that rule names the regional flood elevation, not the flood protection elevation. Commercial structures follow the residential rule. Manufacturing and industrial structures need the lowest floor at or above the flood protection elevation or must meet the floodproofing standards in § 290-40. Buoyant, flammable, explosive or injurious materials are stored at or above the flood protection elevation.

AO and AH zones (§ 290-30A). The lowest floor must meet whichever is higher of three tests: at or above the flood protection elevation, two feet above the highest adjacent grade around the structure, or the depth shown on the FIRM.

Other elevation rules. In existing manufactured home parks, new, replacement and substantially improved homes need the lowest floor elevated to the flood protection elevation and must be anchored (§ 290-27K(2)). Mobile recreational vehicles on site 180 consecutive days or more, or not ready for highway use, meet the same elevation and anchoring rules (§ 290-27L). The Zoning Administrator must see that the regional flood elevation appears on every permit application and keeps records of certified lowest floor elevations (§ 290-36A).