443 flood insurance claims·$7.5M paid·10 federal flood & hurricane disasters
Share of the whole county outline, rivers and lakes included; parts FEMA hasn’t mapped count as zero.
Shaded areas are FEMA’s mapped flood hazard zones in and around Union County, South Dakota. Zoomed out they are simplified; at street level the map switches to FEMA’s exact layer. Tap anywhere to check that spot, or search an address above.
River flooding and regular floods dominate Union County, accounting for 141 recorded events compared to 19 flash floods over the last 30 years. Recent severe events include a multi-day heavy rainfall event from June 20 to June 22, 2024, which brought widespread rain totals between 5 and 15 inches, leading to major river crests, widespread overland flooding, and devastating impacts across southeast South Dakota. Additionally, thunderstorms on July 23, 2025, produced 2 to 5 inches of rain in a matter of hours, causing significant flash flooding.
National Flood Insurance Program claims data demonstrates risk across multiple zones. Properties in Zone X recorded 316 claims with an average payout of $39,440 and an average recorded water depth of 6 inches. Zone A properties experienced 124 claims with an average payout of $35,835 and an average recorded water depth of 11 inches. Zone X_UNSHADED recorded 2 claims averaging $1,000 with an average water depth of 1 inch, while Zone UNKNOWN recorded 1 claim with a $0 payout and 0 inches of recorded water depth.
Homeowners and real estate agents in Zone A should pay the closest attention due to higher average water depths and concentrated claim payouts, though residents in Zone X also face substantial flood risk based on the high volume of historical claims.
Summary written from NOAA storm reports and NFIP claims for this county. Not a prediction.
2% of Union County’s flood insurance claims were on properties rated outside FEMA’s high-risk zones.
126 NFIP claims with a recorded rated flood zone, 1978 to date. The zone is the one FEMA used to rate that policy, which may not match today’s map. Source: OpenFEMA NFIP claims.
In flood insurance claims here that reported a flood depth, the average was 7 inches.
Drawn to scale against an 80-inch door. Even a few inches soaks flooring, the bottom of the drywall and anything plugged in near the floor.
Average of the depths reported on claims (zero and implausible values left out); FEMA’s record doesn’t say exactly where each depth was measured. Source: OpenFEMA NFIP claims.
The worst year was 2011, with 366 claims and $4.3M paid, the year of Flooding.
Bar height is scaled by square root so ordinary years stay visible next to the worst one. NFIP claims by year of loss. Source: OpenFEMA.
45 NOAA storm reports from Union County describe what happened, in the words of the forecasters who covered it. Read the South Dakota flood stories →
19 federal disaster declarations since 1969, 10 of them floods, coastal storms or hurricanes.
| Disaster | Began |
|---|---|
| Severe Storms, Straight-line Winds, And Flooding | Jun 16, 2024 |
| Severe Storms, Tornadoes, And Flooding | Sep 9, 2019 |
| Severe Storms And Flooding | May 21, 2019 |
| Severe Winter Storm, Snowstorm, And Flooding | Mar 13, 2019 |
| Severe Storms, Tornadoes, And Flooding | Jun 13, 2014 |
| Severe Storms, Tornado, And Flooding | May 24, 2013 |
| Flooding | Mar 11, 2011 |
| Severe Storms And Flooding | Sep 22, 2010 |
Weather and water disasters only; most recent first. Source: OpenFEMA Disaster Declarations.
160 since 1996: 19 flash floods and 141 river or area floods.
| Event | Date | Damage |
|---|---|---|
| Flash Flood | Jul 24, 2025 | — |
| Flood | Jun 24, 2024 | — |
| Flood | Jun 23, 2024 | — |
| Flood | Jun 21, 2024 | — |
| Flood | Jun 21, 2024 | $54.5M |
| Flood | Jun 20, 2024 | — |
| Flood | Jul 1, 2024 | — |
| Flood | Mar 16, 2023 | — |
— = no damage estimate in the record. Source: NOAA Storm Events Database.
Flash Flood · Jul 24, 2025. A cluster of thunderstorms erupted within a very moist and unstable airmass ahead of a slow moving frontal boundary during the evening of July 23. These thunderstorms bisected the city of Sioux Falls from southwest to northeast with neighborhoods southeast of I-229 reporting 2 to 5 inches of rain in a matter of 1-2 hours. This resulted in significant flash flooding across impacted portions of the city. Later in th…
Flood · Jun 24, 2024. A multi-day significant heavy rainfall event from June 20-22 resulted in widespread rain totals between 5 and 10 inches with pockets in excess of 15 inches across portions of southeast South Dakota, northwest Iowa, and southwest Minnesota. As rainfall reached area streams and rivers, major to record flooding was observed, devastating several towns and communities. Extensive overland flooding also resulted in signi…
Flood · Jun 23, 2024. A multi-day significant heavy rainfall event from June 20-22 resulted in widespread rain totals between 5 and 10 inches with pockets in excess of 15 inches across portions of southeast South Dakota, northwest Iowa, and southwest Minnesota. As rainfall reached area streams and rivers, major to record flooding was observed, devastating several towns and communities. Extensive overland flooding also resulted in signi…
Flood · Jun 21, 2024. A multi-day significant heavy rainfall event from June 20-22 resulted in widespread rain totals between 5 and 10 inches with pockets in excess of 15 inches across portions of southeast South Dakota, northwest Iowa, and southwest Minnesota. As rainfall reached area streams and rivers, major to record flooding was observed, devastating several towns and communities. Extensive overland flooding also resulted in signi…
National Weather Service narratives, lightly trimmed. Source: NOAA Storm Events Database.
Every colour on the map above is a place on this drawing: where the ground sits relative to the flood FEMA plans for.
If a building in Union County is in a high-risk zone (A or V) and its mortgage comes from a federally regulated or insured lender, or is federally backed, flood insurance is required.
Outside those zones it is optional, and often worth having: from 2014 to 2024 nearly one-third of NFIP claims came from outside the high-risk Special Flood Hazard Area. Since Risk Rating 2.0, NFIP premiums are set for each building, so the only reliable price is a quote: FloodSmart.gov or a local agent.