Blog · October 14, 2026 · South Dakota
Union County Flood Zone Map: checking a property's flood zone
Flood zones are set by FEMA, and checking one near Elk Point takes a few minutes.
Main page: Union County, SD GIS & Parcel Viewer (official map link, county facts and neighboring maps).
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Ahead of any purchase around Big Sioux River, check the Union County flood zone map: FEMA's zone label affects insurance, building rules and resale. What this Union County guide covers: finding the address on FEMA's map, decoding A, AE and X, and pairing it with the Union County Beacon site.
The Union County flood zone map: start here
For a more interactive look, open the National Flood Hazard Layer viewer, which draws the zones over aerial imagery, for land near Missouri National Recreational River included. Vacant ground around Dakota Dunes can still be found: zoom in from the nearest road and click inside the land.
Opening the official parcel viewer
Begin with the Union County Beacon site; it covers each assessed parcel from Beresford to Alcester. When a rural tract has no street number, pan along the nearest road and click the parcel itself, for land near Missouri River included. For property near Beresford, save the parcel ID before closing the panel; each clerk in the county asks for it first.
Next door to Union County
The county meets Plymouth County, IA, Sioux County, IA, Woodbury County, IA, Dakota County, NE, and Dixon County, NE, and each of those keeps its own parcel map for land near Beresford. A tract near the line by Elk Point can be split in two county records, so check the adjacent map too. If you're looking near Missouri National Recreational River, our state page lists every neighboring county map for South Dakota.
Reading A, AE and X
For a home near North Sioux City, A and V zones are Special Flood Hazard Areas, land with a 1-percent chance of flooding in any year. For a parcel near Beresford, a shaded X area marks moderate flood hazard, roughly the 100- to 500-year range; plain X, or C on older maps, means minimal mapped risk.
Places you'll see on the map
Elk Point serves as the county seat, home to the main records offices. Smaller places on the map include Alcester, Beresford, Jefferson, and North Sioux City. Around 17,183 people call Union County home (Census Bureau estimate, 2023) spread over about 461 square miles. The county was formed in 1862, so old deeds can run back a long way around Jefferson. Features like Big Sioux River, Missouri River, and Adams Homestead and Nature Preserve are easy to spot when you zoom out.
Matching the zone to the lot lines
FEMA doesn't draw property lines, so open the Union County Beacon site next to confirm you have the right parcel near Elk Point.
Backing up the map with records
If the land is near Richland, the map is an index, not the title: recorded deeds, plats and easements for parcels in the county sit with the Register of Deeds. Long-held tracts near Big Sioux River may trace back through many deeds, so a title company earns its fee on a real sale.
Insurance, lenders and building
If a building sits in a Special Flood Hazard Area and the loan is federally backed or regulated, mandatory purchase rules apply in communities in the NFIP, whether the land is near Richland or elsewhere in the county. Remodeling a house in a zone near Dakota Dunes usually means extra permit review; ask the local floodplain administrator early.
Limits of the parcel data
If you're looking near Dakota Dunes, listed acreage is a tax-roll number; just a licensed surveyor can set the real lines on the ground. Out toward Dakota Dunes, records update in batches, so a deed recorded last month can take weeks to appear.
Taking the map into the field
The parcel map usually runs in a mobile browser, which helps when you're standing on land near Dakota Dunes, though signal can drop in rural spots. A saved image of the lot near Elk Point and its lines helps when you meet an owner or agent.
Low spots and local drainage
Small streams around Missouri National Recreational River may not have detailed mapping, so look for water marks and debris lines. Wet ground around Missouri National Recreational River is a separate issue from flood zones; the National Wetlands Inventory mapper shows mapped wetlands.
What to request from a seller
For land near Missouri National Recreational River, ask the seller whether the home has flooded before closing; getting a quote early avoids surprises.
Union County: common questions
Does the county parcel map show flood zones around Missouri National Recreational River?
Good question; a flood layer may appear in the county Beacon site layer list; confirm a lot near Alcester on FEMA's map either way.
Is AE a high-risk flood zone near Dakota Dunes?
It depends, but AE is a Special Flood Hazard Area with a published base flood elevation, which shapes building rules near North Sioux City.
Can a property in Zone X near Elk Point flood?
On ground around Dakota Dunes, shaded X is moderate risk and unshaded X is minimal risk, and floods still happen outside high-risk zones.
Can a flood zone near Alsen change?
Usually, a new study can move a zone line near Big Sioux River; check the effective date on the panel.
Where is the legal description for land near Elk Point?
Near North Sioux City, it's the formal description of the land in the deed, and the parcel record often summarizes it.
Open the official Union County, SD parcel map See it 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.