Tucson, AZ Environmental Rules: Flood Elevation Requirements (2026)

Chapter 26 of the Tucson Code splits floodplain land into the floodway, where development is largely barred, and the floodway fringe, where people and the watercourse can share space if the arrangement doesn't cause damage. 2 sets the fringe's development standards, and subsection (9) is the freeboard rule: the lowest floor of any structure, including a basement, must sit at least one foot above the base flood elevation established for that reach of the watercourse. In an AO Zone, where FEMA has mapped flood depths rather than a specific numbered elevation, new residential construction and substantial-damage repairs must instead be elevated to or above the regulatory flood elevation set for that zone.

Compliance is checked twice during construction. Before the first floor slab is poured or the lowest floor framing goes in, and before any framing begins, the applicant must give the city engineer a certification from a state-registered land surveyor or state-registered professional civil engineer confirming the framework elevation matches what the city engineer's office approved. That certification is submitted on FEMA's Elevation Certificate form, once as the preslab 'Building Under Construction' version and again at the 'Finished Construction' stage. Subsection (5) of the same section caps how much floodway fringe development can raise the base flood elevation for others: no more than one-tenth of a foot measured from the property boundary, which keeps upstream and downstream properties from absorbing added flood risk from new fill or structures.

The city engineer administers these standards and, under Section 26-3(b), also determines base flood elevations by engineering study on watercourses where FEMA's flood insurance rate maps don't already show a numbered elevation.