446 flood insurance claims·$31.4M paid·12 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 Johnson 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 Johnson County, with NOAA Storm Events Database records showing 49 flash flood events compared to 25 general flood events over the last 30 years. Recent events illustrate this pattern, including heavy rainfall of 2 to 3.50 inches and flash flooding near Iowa City and south of Interstate 80 on July 2, 2024, as well as heavy rain leading to flash flooding in the Iowa City metropolitan area on July 10, 2024.
National Flood Insurance Program records indicate that flood risks extend beyond high-risk areas. Properties in Zone A recorded 294 claims with an average water depth of 23 inches and an average payout of $88,566. Meanwhile, properties in Zone X recorded 91 claims with an average water depth of 25 inches and an average payout of $85,902, and Zone X_SHADED recorded 43 claims with an average water depth of 6 inches and an average payout of $81,098. Zone X_UNSHADED properties recorded 15 claims with an average water depth of 11 inches and an average payout of $36,073, while Zone UNKNOWN recorded 3 claims with an average water depth of 2 inches and an average payout of $19,904.
Homeowners, real estate agents, and journalists should pay the most attention to properties located within both designated high-risk zones and moderate-to-low risk Zone X areas, where significant claim counts and recorded water depths demonstrate vulnerability to heavy rainfall.
Summary written from NOAA storm reports and NFIP claims for this county. Not a prediction.
16% of Johnson County’s flood insurance claims were on properties rated outside FEMA’s high-risk zones.
352 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 21 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 181 claims and $26.9M 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.
23 NOAA storm reports from Johnson County describe what happened, in the words of the forecasters who covered it. Read the Iowa flood stories →
24 federal disaster declarations since 1965, 12 of them floods, coastal storms or hurricanes.
| Disaster | Began |
|---|---|
| Severe Storms | Aug 10, 2020 |
| Severe Storms, Tornadoes, Straight-line Winds, And Flooding | Jun 26, 2014 |
| Severe Storms, Tornadoes, And Flooding | May 19, 2013 |
| Severe Storms, Straight-line Winds, And Flooding | Apr 17, 2013 |
| Severe Storms, Tornadoes, And Flooding | May 25, 2008 |
| Severe Winter Storm | Dec 10, 2007 |
| Severe Winter Storms | Feb 23, 2007 |
| Hurricane Katrina Evacuation | Aug 29, 2005 |
Weather and water disasters only; most recent first. Source: OpenFEMA Disaster Declarations.
74 since 1996: 49 flash floods and 25 river or area floods.
| Event | Date | Damage |
|---|---|---|
| Flash Flood | Jul 10, 2024 | — |
| Flash Flood | Jul 2, 2024 | — |
| Flash Flood | Jun 25, 2022 | — |
| Flash Flood | Jul 8, 2022 | — |
| Flash Flood | Jun 27, 2020 | — |
| Flash Flood | Jun 9, 2020 | — |
| Flash Flood | May 29, 2019 | — |
| Flash Flood | May 28, 2019 | — |
— = no damage estimate in the record. Source: NOAA Storm Events Database.
Flash Flood · Jul 10, 2024. Thunderstorms developed in central Iowa and moved across eastern Iowa during the late afternoon and evening hours of July 10th. These storms produced damaging winds and heavy rainfall across the area. Heavy rain led to flash flooding as the storms moved into the Iowa City metropolitan area.
Flash Flood · Jul 2, 2024. A line of organized storms surged into eastern Iowa late in the day and produced severe winds and heavy rainfall. The strongest storms occurred in a swath just south of Interstate 80, including near Iowa City, producing thunderstorm wind gusts of 60 to 80 MPH. There were rainfall amounts of 2 to 3.50 inches.
Flash Flood · Jun 25, 2022. Several intense clusters of storms moved through eastern Iowa into Illinois. The morning cluster produced flash flooding. In the afternoon and evening, a cluster of intense thunderstorms moved through far eastern Iowa into west central and northwest Illinois the evening of June 25th, with torrential rainfall and wind damage along it's way.
Flash Flood · Jul 8, 2022. Rain showers produced heavy rain of 3 to 5 inches across the warned area. This led to flash flooding in Johnson county and Muscatine County.
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 Johnson 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.