Blog · October 14, 2026 · South Dakota
Deuel County Flood Zone Map in South Dakota
FEMA's free flood maps and the Deuel County parcel viewer, used together for property near Brandt.
Main page: Deuel County, SD GIS & Parcel Viewer (official map link, Deuel County facts and neighboring maps).
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A Deuel County flood zone map check belongs in the due diligence for any Deuel County property, from a house lot in Gary to farm ground near Altamont. For any tract in Deuel County, South Dakota, the answer affects insurance, permits and resale.
Below are the FEMA links, a plain reading of the zone labels, notes on where water shapes land around Gary, and short answers to common questions.
How to use the Deuel County flood zone map
Open the FEMA Flood Map Service Center and type a county street address, say one in Altamont. If a piece of ground near Clear Lake has no street number yet, search the nearest road and pan to it. On acreage outside Altamont, the National Flood Hazard Layer viewer is easier to use; zoom to the piece of ground near Clear Lake and click. Next, the Deuel County parcel viewer confirms which Deuel County parcel you're looking at. Laying the county parcel outline beside the FEMA shading displays whether a homesite near Clear Lake sits above or inside the zone.
Step one: the free Deuel County viewer
The county's own public map is the Deuel County parcel viewer, and it opens without an account for parcels in Astoria and the rest of the county. Use the search box for an address in Astoria or a parcel number, or simply zoom in and click a piece of ground near Toronto. For a backup route to the map covering Toronto, our Deuel County directory entry keeps the link current.
What the flood zone letters mean
On the FIRM covering Deuel County, zones that start with A or V are Special Flood Hazard Areas, defined by a 1-percent annual chance of being flooded. Zone AE near Clear Lake means FEMA published a base flood elevation; plain Zone A means no detailed elevation was studied. Land near Clear Lake in shaded X (Zone B on older maps) sits in the moderate band between the 100-year and 500-year floods. Unshaded Zone X near Clear Lake is minimal risk.
Unmapped creeks in Deuel County
Small streams and ditches near Altamont may not be studied in detail can still flood; FEMA says moderate- and low-risk areas still carry risk.
The lay of the land around Clear Lake
Clear Lake is the county seat, and Gary, Altamont, Astoria, and Brandt are among the other towns on the county map. Unincorporated communities in the county, including Bemis, Johnsonville, and Moritz, display up as small groups of parcels along the roads. Deuel County had an estimated 4,354 people in 2023 (Census Bureau), spread across about 623 square miles. Outside Gary, most of the county map is farm, ranch or timber ground with large, irregular tracts.
Deuel County land records
For land near Astoria, the deed itself lives in the county recording office, and the map is an index to it. Copy the parcel number and legal description from the county record well before you request a deed for land near Toronto.
Tracts that cross the Deuel County line
A farm near the county line can carry separate records in Lac qui Parle County, MN, Lincoln County, MN, and Yellow Medicine County, MN as well. Our South Dakota page links each map neighboring Deuel County.
When the map affects a deal
Lenders watch the zone closely on Deuel County properties. Where a building in Altamont is mapped in a high-risk zone and is financed by a regulated or federally insured lender, flood insurance is mandatory, provided the community near Altamont takes part in the National Flood Insurance Program. In Zone X near Altamont, coverage is optional, although some lenders require it anyway. Where a structure near Altamont looks higher than the shading suggests, FEMA's LOMA process allows a review, supported by elevation data from a licensed land surveyor. Placing fill on low ground near Altamont commonly requires a permit and an elevation check; the county floodplain administrator can say what applies.
Quick answers for Deuel County
What does BFE mean on the flood map for Brandt?
On the map covering Brandt, the base flood elevation marks how high the 100-year flood is expected to rise, and a surveyor compares the building near Brandt to it.
My lot in Brandt displays Zone AE. What does that mean?
For a Deuel County parcel, Zone AE means a Special Flood Hazard Area with a 1-percent annual chance of flooding and a published base flood elevation.
Is flood insurance required for a Zone X lot in Brandt?
FEMA doesn't require it for a Zone X lot in Brandt, but coverage is available and some lenders ask for it.
What does 100-year flood mean for Deuel County land?
Not at all; a Deuel County tract in that zone has a 1-percent chance of flooding every year, so floods can come in back-to-back years.
How do I know if a property in Deuel County is in a flood zone?
Look it up at FEMA's Flood Map Service Center, then match the parcel lines in the county parcel viewer; for land near Astoria, a zone starting with A or V is high risk.
Do I need a permit to build in the floodplain near Brandt?
Often, but local floodplain rules apply; ask the county or town building office in Brandt well before you buy.
Open the official Deuel County, SD parcel map Deuel County in the Platbookmapper directory
Not a survey. County GIS and tax parcel maps are assessment and planning layers. They are not a substitute for a recorded plat, deed, or licensed survey, especially for fences, setbacks, or boundary disputes.