FEMA expects more hazard damage per building in Rock Valley than in 69% of U.S. towns, mostly from river and rain flooding
On FEMA’s National Risk Index, Rock Valley gets a C for hazard risk: higher expected damage per building than 69% of U.S. towns, #110 of 140 in Iowa. Most of that expected damage is river and rain flooding (74%), then tornadoes (19%). Flood insurance has paid 12 claims here since 2014.
Graded on FEMA’s expected yearly building damage per dollar of building value (NRI v1.20, December 2025), weighted by where residents live; flood claims are shown, not graded. How hazard risk is graded
What Rock Valley faces
Each hazard’s share of the building damage FEMA expects here, and how its rate compares with the rest of the country.
River and rain flooding
Tornadoes
Shares are of FEMA’s expected building damage, the measure the grade uses; ranks compare each hazard’s building-damage rate with all 85,154 U.S. census tracts. In FEMA’s terms, river and rain flooding is FEMA’s “Inland Flooding” (rivers and streams overflowing their banks, or rain overwhelming drainage). FEMA defines coastal flooding as high or rising tides and storm surge, so surge damage is counted there. Drought isn’t listed: FEMA counts its losses in crops only.
What’s behind Rock Valley’s grade
River and rain flooding is 74% of the building damage FEMA expects in Rock Valley, and Rock Valley’s rate of river and rain flooding damage is higher than 74% of U.S. census tracts. Tornadoes add 19%, at a rate in the top 1% of U.S. census tracts.
C #110 of 140 in Iowa; higher expected damage per building than 69% of U.S. towns (21,298).
All of Rock Valley’s residents live in one census tract; the figures are that tract’s.
The typical Iowa town has lower expected damage than 57% of U.S. towns; within the state, Rock Valley has more expected damage per building than 78% of Iowa towns.
In dollars, FEMA expects about $4.5M a year in losses across Rock Valley: $3.0M to buildings, the rest to people and crops.
Does Rock Valley flood? Sometimes: 12 flood claims since 2014
Every paid claim on a federal flood insurance policy in Rock Valley, from FEMA’s records: 8.2 per 1,000 homes, more than 70% of the 13,809 U.S. towns with a flood insurance record.
- The June Midwest Flooding8 claims · $1.1M
- The Iowa Flooding1 claim · $276K
Rock Valley isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.
Insurance rates: Sioux County.7 federal disasters brought FEMA money to Rock Valley
Disasters that paid out in Rock Valley itself (aid to households or repair grants to the City of Rock Valley), newest first, with that year’s flood claims.
- 2024Severe Storms, Flooding, Straight-line Winds, and Tornadoes656 households applied for aid$15.0M aid approved$22.9M to the City of Rock Valley for repairs9 flood claims paid that year
- 2019Severe Storms and Flooding$119K to the City of Rock Valley for repairs
- 2018Severe Storms, Tornadoes, Straight-line Winds, and Flooding$479K to the City of Rock Valley for repairs2 flood claims paid that year
- 2014Severe Storms, Tornadoes, Straight-line Winds, and Flooding$723K to the City of Rock Valley for repairs1 flood claim paid that year
- 2013Severe Winter Storm$46K to the City of Rock Valley for repairs
- 2010Severe Storms, Flooding, and Tornadoes8 households applied for aid$1K aid approved
Show all 7
- 2009Severe Winter Storms and Snowstorm$15K to the City of Rock Valley for repairs
Sioux County has had 12 natural disasters declared by the President since 1953, most often severe storms, then floods. Not counted: the 2005 Hurricane Katrina evacuee emergency, which covered counties that took in evacuees.
Old photos of Rock Valley after a storm or flood belong in the town’s history. Add one, or share what you remember below.
Add to the Rock Valley archive →Get ready for what Rock Valley faces
A short kit for the hazards that drive the building damage here, what to check before you buy, and where neighbors get alerts.
- Turn around at flooded roads: a foot of moving water can carry off a car.
- Flood insurance usually takes 30 days to start, so buy it before the forecast.
- Keep papers and medicines up high, in a grab-and-go bag.
- Pick your spot now: the lowest floor, an inside room, no windows.
- A watch means be ready; a warning means take cover now.
- Keep shoes and a flashlight by the bed.
- Look up the address on FEMA’s flood map.
- Ask the seller or landlord whether it has ever flooded, and what flood insurance costs there.
- Get a flood insurance quote early: policies usually start 30 days after you buy.
Know where neighbors sign up for alerts? Add it to the Handbook so everyone has it.
Questions about natural hazards in Rock Valley
Is Rock Valley at risk for natural disasters?
On FEMA’s National Risk Index, Rock Valley has higher expected damage per building than 69% of U.S. towns: C for hazard risk, #110 of 140 in Iowa. Most of the expected damage is river and rain flooding (74%) and tornadoes (19%). The figures are for the one census tract the town shares with its neighbors. This is FEMA’s model of an average year for today’s buildings, not a forecast.
Does Rock Valley flood?
Flood insurance has paid 12 claims in Rock Valley since 2014, $1.4M in all, or 8.2 per 1,000 homes, more than 70% of U.S. towns with a flood insurance record. 1 properties have flooded more than once. The most claims came from June Midwest Flooding (8).
Is Rock Valley in a flood zone?
Flood zones are drawn street by street, so the answer depends on the address: look it up on FEMA’s flood map. In Sioux County, 1.2% of all homes carry federal flood insurance.
How much is flood insurance in Rock Valley?
FEMA’s Community Rating System list shows no discount for Rock Valley’s flood program. Premiums depend on the building; policies usually start 30 days after you buy, so get a quote early.
What was the biggest storm in Rock Valley?
By FEMA money that reached Rock Valley, Severe Storms, Flooding, Straight-line Winds, and Tornadoes (2024): 656 households applied for aid, $15.0M approved, and $22.9M to the City of Rock Valley for repairs. By flood claims, June Midwest Flooding: 8 paid, $1.1M.
Is Rock Valley at risk from river and rain flooding?
It is the largest share of the building damage FEMA expects here (74%), and Rock Valley’s rate for it is higher than 74% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in Rock Valley.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Rock Valley’s residents lived in the 2020 census; OpenFEMA: NFIP redacted claims, multiple-loss properties, community status book and residential penetration rates, housing assistance (owners and renters), public assistance funded projects, hazard mitigation properties and disaster declarations. Homes: Census ACS 2020–24. Preparedness tips: Ready.gov. FEMA’s model is an average of expected damage, not a forecast. How hazard risk is graded.