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Alluvial Soils and Floodplains



Alluvial soils are soils deposited by running water and are often located in existing floodplains. The DNR has developed an animal feeding operations (AFO) Siting Atlas that producers can check to determine if a potential animal feeding operation site would be located on alluvial soils, and, thus, possibly in a floodplain. Instructions for using the alluvial soils maps are available on the Proper AFO Siting webpage. See floodplain requirements below for confinements and for open feedlots.
Rivers and streams just naturally flood. The AFO Siting Atlas provides information about alluvial soils and floodplains to help producers avoid building in these areas. NRCS photo on right.

Above: Rivers and streams just naturally flood. The AFO Siting Atlas provides information about alluvial soils and floodplains to help producers avoid building in these areas. NRCS photo on right.

Floodplain Requirements for Confinement Feeding Operations

State law requires anyone wishing to build, modify or expand a confinement or manure storage structure located on alluvial soils to determine if the proposed site will be located in a 100-year floodplain. State law prohibits construction of a confinement in the 100-year floodplain of a major watersource. Use the DNR AFO Siting Atlas to check if your proposed site is on alluvial soils. You will need to know the township, range and section of the proposed location. Please document your findings from the map and submit that document with your construction design plans. Small animal feeding operations - please keep a copy of the documentation on-site, unless a construction permit is needed.

  • Confinements with less than 1,000 animal unit capacity using formed structures:

If the proposed location of a confinement with less than 1,000 animal units is located on alluvial soils, the producer must petition the DNR for a declaratory order to determine if the site is in a 100-year floodplain. The petition must follow the format outlined in the 561 Iowa Administrative Code (IAC), 6.7. The DNR has developed a form for producers' convenience, Petition for a Declaratory Order, Form 542-8157, which animal producers may use.

  • Confinements needing a construction permit:

If the proposed site of a confinement with 1,000 animal units or more is located on alluvial soils, the construction permit applicant must request a floodplain determination from the DNR. The determination is different than the petition for a declaratory order. For a floodplain determination contact Kelly Stone at 866-849-0321.

Floodplain Requirements for Open Feedlots

While open feedlots are not prohibited from constructing in alluvial soils, they must meet certain DNR requirements. For proposed open feedlot structures, a floodplain construction permit must be obtained if the drainage area is greater than 10 square miles. Producers can use the DNR's AFO Siting Atlas to determine if a proposed site is in alluvial soils. Then contact the DNR Flood Plain section at 866-849-0321. 


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