Olmsted County, MN Environmental Rules: Flood Zones (2026)

Floodplain regulation in Minnesota is anchored in Minn. Stat. Ch. 103F (Public Waters), specifically §§103F.101-103F.165, which require local governments with mapped floodplains to adopt and enforce a floodplain ordinance meeting Department of Natural Resources standards. Counties and cities must also satisfy federal NFIP rules at 44 CFR Parts 59-60 to keep their communities eligible for federally backed flood insurance. Olmsted County adopted Chapter 3750 - Floodplain and Shoreland Ordinance (Ordinance No. 23-5) to comply with both frameworks. Chapter 3750 regulates development in the FEMA-mapped Special Flood Hazard Area along the Zumbro River and its tributaries, including the floodway, flood fringe, and general floodplain districts. Under Chapter 3750, any change to base flood water surface elevations requires notification to FEMA and approval by the Minnesota DNR. The ordinance is administered and enforced by the Olmsted County Planning Department. New residential structures in the SFHA must have the lowest floor elevated above the regulatory flood protection elevation set by the ordinance (Minnesota's statewide minimum is one foot above the base flood elevation per DNR rules at Minn. Rules Ch. 6120). Substantial improvements - those equal to 50% or more of the structure's pre-improvement market value - trigger full floodplain compliance. The City of Rochester has a separate floodplain overlay within its UDC. FEMA Flood Insurance Rate Maps for Olmsted County can be obtained through the FEMA Map Service Center.