Lyon County, NV Environmental Rules: Flood Zones (2026)

Lyon County Code section 15.800.08A requires a floodplain development permit before construction or development begins in any area of special flood hazard mapped under section 15.800.07A. The permit covers every structure, including manufactured homes, accessory dwelling units and accessory structures, whether or not a separate building permit applies, and every development activity including fill placement and river bank or stream bank erosion repair. Applications go to Community Development on department forms with applicable fees; the applicant must supply lowest floor elevation data, a Nevada-licensed engineer or architect's flood proofing certification for nonresidential structures, and, for any watercourse alteration, a No-Rise certificate supported by a FEMA conditional letter of map revision or letter of map revision.

Where base flood elevation data is unavailable, the applicant must generate it for any subdivision or development of fifty lots or five acres, whichever is less. The Director or designee, as Floodplain Administrator, reviews every application under section 15.800.08C to confirm required federal, state and local permits are in hand and that the site and structures are reasonably safe from flooding, and that the project will not raise the base flood water surface more than half a foot at any point. Larger proposals of five parcels or more also go to the Planning Commission and Board of County Commissioners, weighed against the county's master plan and multi-jurisdictional hazard mitigation plan before approval.