Floodplain Regulations

Certain types of development within the floodplain is generally allowed, but proper floodplain management aims to minimize risk from potential flood hazards. Landowners should work with their local government for floodplain-related development. 

Communities use their floodplain ordinance in conjunction with FEMA-approved maps to guide land use decisions. The DNR assists local communities by providing general regulatory assistance.

Contact information

Permits and zoning regulations

  • City - If your property is within the boundary of a city, contact your city.
  • Unincorporated Area of the County - If your property is not within a city, contact your county zoning authority.
  • Townships with Floodplain Zoning - In some cities, townships administer floodplain management permits and zoning rather than the county. Contact your township officials directly.

FEMA maps and flood elevations

What is a floodplain?

The Federal Emergency Management Association (FEMA) defines floodplain very broadly as “any area of land susceptible to being inundated by floodwaters from any source.” This is typically the areas outside the channel or banks of a waterbody. A floodplain, when allowed to function naturally, helps to slow stormwater runoff, improve water quality, and encompasses some of our most critical habitat and ecosystems.

A typical FEMA floodplain map, and the associated modeling data, is most typically associated with the “100-year” (or base flood elevation, or 1% percent annual chance) floodplain. For some areas, other data may be available identifying other recurrence intervals, such as the “10-year” (10% annual chance) or “500-year” (0.2% annual chance) floodplain. Minnesota has been documenting more water and extreme events due to climate change, and has seen floods meeting or exceeding 100-year intervals more frequently than has been historically observed.

From a regulatory standpoint – as it guides land uses, alterations, and other activities – floodplains are regulated based on the Regulatory Flood Protection Elevation, which is typically one (1.0’) to one and half (1.5’) above the 1% annual chance floodplain. Floodplains are also comprised of a floodway and flood fringe. However, these details may not always be identified on official floodplain maps.

100-year floodplain diagram

What is the floodway?

The floodway is the land immediately adjoining the river channel that is the natural conduit for flood waters. The floodway must remain open in order to allow flood waters to pass. When the floodway is obstructed by buildings, structures, or debris, flood waters will be dammed up and will flood even greater areas. Large portions of the floodplain store and later release flood waters, which reduce river flood stages.

Under statewide floodplain management standards, communities can designate areas for development in the floodplain, called flood fringe areas, that would cumulatively cause no more than a six-inch stage increase in the 100-year flood. A lesser stage increase than six inches would be appropriate where filling/development of proposed flood fringe areas would increase flood damage potential to nearby properties.

Many communities have delineated the boundary of the floodway and flood fringe on zoning maps. If the property a person owns or is interested in buying lies within this mapped floodway, they will not be permitted to construct a dwelling or other enclosed structure, place fill material, or obstruct flood flows in any other way. Since this area must be left open to pass flood waters, only open space uses, such as farm land, residential yards or gardens, golf courses, parks, playgrounds, or parking areas, are normally allowed in the floodway.

What is the flood fringe?

The flood fringe is the remainder of the floodplain lying outside of the floodway. This area is generally covered by shallow, slow moving flood waters. Development is normally allowed in the flood fringe provided that residential buildings are placed so that the lowest floor, including the basement, is above the flood protection elevation. In areas where the floodplain maps do not delineate the floodway and flood fringe, a permit applicant will likely be asked to provide certain engineering information to verify the flood protection elevation of the site , and that it is outside of the floodway before they could build a structure in the floodplain.

What is the flood protection elevation?

The flood protection elevation refers to an elevation 1 foot above the 100-year flood plus any stage increase due to the designation of flood fringe areas. Some communities may designate a higher flood protection elevation to further reduce risk. The elevation of the lowest floor of a dwelling must be at or above the flood protection elevation. Local regulations will also require the top of the access road elevations to be within 2 feet of the flood protection elevation.

What is a flood insurance rate map?

FEMA works with the State of Minnesota and its communities to conduct flood studies and identify special flood hazard areas (SFHAs) on flood maps, known as Flood Insurance Rate Maps. They incorporate a variety of information, are publicly available, and are most often used by planning professionals, engineers, lenders, and insurance agents.

Why are the existing flood insurance rate maps being updated?

New data and modern hydraulic and hydrologic engineering methods are now being used to map floodplains more accurately than they once were. Additionally, newer maps are much more readily accessible in a digital format.

How do I know if my property or house is in the floodplain?

The DNR's Find Flood Maps page details the maps available throughout the state. Your local government may have access to better local data available or preliminary mapping data. Property owners are encouraged to contact their local official for the best available data.

Why is my building in the floodplain? How can I challenge this?

Once the 100-year flood elevation is determined, the boundaries of the floodplain are delineated using a topographic map. The burden of proof to challenge such "in or out" decisions and mandatory insurance purchase requirements rests with the owner. The property owner may file a Letter of Map Amendment (LOMA) with FEMA to appeal a boundary determination. Your local community should be able to help guide you through this process. Additional guidance for obtaining a LOMA is available.

Can I build in the floodplain?

Construction and fill is generally permitted in portions of the floodplain, provided they adhere to their community’s floodplain management ordinance. Such projects as building a house, placement of fill, or installing a culvert or bridge would all require a floodplain permit.

 

What is floodproofing?

Flood proofing includes a variety of construction methods, such as watertight doors, windows, walls, and bulkheads, which can be used to prevent flood waters from entering a structure. This method of flood protection, called "dry" flood proofing is not a sure deterrent to flooding and is used only in very special circumstances where it may not be possible to place the building or accessory structure on fill. Local floodplain regulations restrict dry flood proofing to non-residential structures. New residential basements are prohibited unless the community has been granted a residential basement exemption from the Federal Emergency Management Agency (FEMA). "Wet" flood proofing, which involves intentional internal flooding of areas constructed of flood resistant materials, may be allowed for minor additions to structures and certain accessory structures that constitute a minimal investment. Furthermore, state and federal floodplain management standards require all flood proofed structures to be designed and certified by a registered architect or engineer.

Floodplain management informational sheets

Floodplain administration resources

Questions

  • Ceil Strauss, State Floodplain (NFIP) Manager, 651-259-5713

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