14 flood insurance claims·$133,648 paid·6 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, Iowa. 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.
Flash flooding from summer thunderstorms dominates Union County, accounting for 26 out of 39 recorded flood events over the last 30 years, alongside 13 general flood events. Heavy rainfall events are driven by stationary boundaries, shortwave activity, and warm fronts moving from Missouri that cause slow-moving storms to repeatedly drop rain over the same areas. For example, a slow-moving warm front on July 11, 2015, brought over 4 inches of rain to parts of southern Iowa with totals reaching up to 5.75 inches near Lorimor, resulting in localized flash flooding. Wet conditions and saturated soils further amplified risks during events such as the moderate to heavy rainfall on September 5, 2018, and storms fueled by high precipitable water values on June 25, 2019.
Homeowners, real estate agents, and journalists should pay attention to properties across multiple FEMA zones where historical claims have occurred. NFIP records show claims and water depths varying by zone, including Zone X with an average of 12 inches of recorded water depth across 6 claims, Zone A with an average of 28 inches of recorded water depth across 3 claims, Zone X shaded with an average of 12 inches of recorded water depth across 3 claims, and Zone X unshaded with an average of 3 inches of recorded water depth across 1 claim.
Summary written from NOAA storm reports and NFIP claims for this county. Not a prediction.
In flood insurance claims here that reported a flood depth, the average was 15 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 2008, with 4 claims and $95,631 paid, the year of Severe Storms, Tornadoes, and 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.
34 NOAA storm reports from Union County describe what happened, in the words of the forecasters who covered it. Read the Iowa flood stories →
21 federal disaster declarations since 1969, 6 of them floods, coastal storms or hurricanes.
| Disaster | Began |
|---|---|
| Severe Storms And Tornadoes | Apr 26, 2024 |
| Severe Storms And Flooding | Mar 12, 2019 |
| Severe Storms, Flooding, And Tornadoes | Jun 1, 2010 |
| Severe Winter Storm | Jan 19, 2010 |
| Severe Storms, Tornadoes, And Flooding | May 25, 2008 |
| Severe Winter Storm | Dec 10, 2007 |
| Severe Storms And Flooding | Aug 17, 2007 |
| Severe Storms, Flooding, And Tornadoes | May 5, 2007 |
Weather and water disasters only; most recent first. Source: OpenFEMA Disaster Declarations.
39 since 1996: 26 flash floods and 13 river or area floods.
| Event | Date | Damage |
|---|---|---|
| Flash Flood | Jun 25, 2019 | $10,000 |
| Flash Flood | Sep 5, 2018 | $10,000 |
| Flood | Jul 11, 2015 | $100,000 |
| Flash Flood | Jul 11, 2015 | $50,000 |
| Flood | Sep 10, 2014 | $200,000 |
| Flash Flood | Sep 9, 2014 | $200,000 |
| Flash Flood | May 16, 2013 | $10,000 |
| Flash Flood | Jun 26, 2011 | $10,000 |
— = no damage estimate in the record. Source: NOAA Storm Events Database.
Flash Flood · Jun 25, 2019. During the evening of the 25th, a number of storms were able to initiate along a relatively stationary boundary situated across southern Iowa. On the warm side of the boundary surface conditions were in the mid 80s for temperature and upper 60s to low 70s dewpoints. Additionally, the conditions yielded an environment with 2000-3000+ J/kg SB/MUCAPE, 30-40 kts of effective bulk shear, 500-700 J/kg CAPE in the hail…
Flash Flood · Sep 5, 2018. Wet conditions continued across the state with yet another round of moderate to heavy rainfall on top of already mostly saturated conditions. A shortwave moving through the upper level flow out of the southwest, a surface front situated to the west and northwest of the state, and strong 850 mb flow were the main contributors to showers and storms. ||Conditions were certainly conducive for heavy rainfall, includi…
Flood · Jul 11, 2015. A warm front pushed into southern Iowa from Missouri, bringing with it storms and heavy rainfall. The front progressed slowly, aiding in keeping the rain over the same areas for long periods of time. By the end of the day, a number of areas across the south reported 4+ inches of rain with the highest totals around 5.5-5.75 near Lorimor, Rathbun, Derby, and Humeston. Localized flash flooding ensued.
Flash Flood · Jul 11, 2015. A warm front pushed into southern Iowa from Missouri, bringing with it storms and heavy rainfall. The front progressed slowly, aiding in keeping the rain over the same areas for long periods of time. By the end of the day, a number of areas across the south reported 4+ inches of rain with the highest totals around 5.5-5.75 near Lorimor, Rathbun, Derby, and Humeston. Localized flash flooding ensued.
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.