Coeur d'Alene, ID Environmental Rules: Flood Elevation Requirements (2026)

Chapter 15.32 sets the elevation rule through a definition and a construction standard. The definition of flood protection elevation (FPE) in Section 15.32.040 starts from the one percent (1%) chance annual flood, the 100-year flood, adds any increase due to floodway encroachment and any required freeboard, and then states the city position: the city does not allow an increase in water surface elevation in the floodway and no additional freeboard is required. The FPE is the base flood elevation plus the floodway elevation, if present, plus zero freeboard. The base flood elevation (BFE) is the water surface elevation during the base flood, depicted on the FIRM to the nearest foot and in the FIS to the nearest 0.10 foot, measured against the NAVD88 vertical datum. The code still defines freeboard as a factor of safety in feet above a flood level, meant to cover wave action, obstructed bridge openings, debris and ice jams and the hydrologic effects of urbanization.

Section 15.32.130 applies the FPE to homes. Where BFE data are available, the lowest floor of new residential construction or substantial improvement, including basement, must be at or above the FPE. A fully enclosed area below the lowest floor must be an unfinished or flood resistant enclosure with a minimum of two (2) openings, a total net area of not less than one square inch for every square foot of enclosed area, and the bottom of every opening no higher than one foot (1') above the higher of the exterior or interior grade. The enclosure can only be used for parking of vehicles, limited storage of maintenance equipment or entry to the elevated area, and cannot be partitioned or finished into separate rooms. Below grade crawl spaces are prohibited where floodwater velocity exceeds five feet (5') per second, the interior grade cannot be more than two feet (2') below the lowest adjacent exterior grade, and the crawl space height cannot exceed four feet (4').

Nonresidential buildings in zones A1-30, AE or AH not elevated to the FPE must be floodproofed watertight to the FPE or to one foot (1') above the BFE, whichever is higher, under Section 15.32.140, with a licensed professional engineer or architect certifying the design to the administrator. Section 15.08.005 deletes IRC Section R322 so this chapter governs flood-resistant construction.