Janesville, WI Environmental Rules: Flood Elevation Requirements (2026)

Section 42-489 defines 'Flood protection elevation' as 'an elevation of two feet of freeboard above the water surface profile elevation designated for the regional flood,' which sets Janesville's freeboard margin two feet higher than the base or regional flood level shown on the FIRM. That definition drives the construction standard in Section 42-481(c)(1)a for residential structures in the Floodfringe District: the lowest floor must sit at or above the flood protection elevation on fill, and the fill itself must be at least one foot above the regional flood elevation and extend a minimum of 15 feet beyond the limits of the structure.

Where fill is not used, Section 42-481(c)(1)b allows the basement or crawlway floor to sit at the regional flood elevation only if it is dry floodproofed up to the full flood protection elevation, and no basement or crawlway floor is ever allowed below the regional flood elevation itself. Nonresidential and manufacturing structures in the floodfringe face the same two-foot freeboard target under Section 42-481(c)(3) and (c)(4), either by elevating the lowest floor to the flood protection elevation or by floodproofing to the standards cross-referenced in Section 42-487(f).

The Zoning Administrator relies on certified elevation surveys, not visual estimates, to confirm the two-foot freeboard has actually been achieved before a certificate of occupancy is issued.