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FEMA flood zones · Iowa

Sioux City, Iowa Flood Zone Map

85,797 residents·in Woodbury County·294 flood claims county-wide

Coastal high risk (V, VE)FloodwayHigh risk (A, AE)Moderate (X, 500-year)Minimal (X)Undetermined (D)

Shaded areas are FEMA’s mapped flood hazard zones in and around Sioux City, 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.

Flood risk in Sioux City

The map above shows FEMA’s flood zones in and around Sioux City; tap any spot, or search an address, for the exact zone. FEMA’s flood insurance records are kept by county, not by city, so the numbers below are for all of Woodbury County, which includes Sioux City.

18% of Woodbury County’s area is in FEMA’s high-risk flood zones, and another 2% in shaded X (mostly the 0.2% floodplain and areas behind levees).

Where the flood claims came from

8% of Woodbury County’s flood insurance claims were on properties rated outside FEMA’s high-risk zones.

247 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.

How deep the water got

outlet80″ door12″24″36″48″60″72″84″

In Woodbury County flood insurance claims that reported a flood depth, the average was 3 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 the county’s claims (zero and implausible values left out). Source: OpenFEMA NFIP claims.

Flood claims, year by year

The worst year was 1990, with 152 claims and $808,268 paid, the year of Severe Storms & Flooding.

1978: 10 claims1979: 11 claims1980: 2 claims1981: 2 claims1982: 2 claims1983: 10 claims1984: 4 claims1986: 4 claims1989: 2 claims1990: 152 claims1991: 1 claims1993: 3 claims1994: 1 claims1996: 4 claims1998: 3 claims1999: 2 claims2000: 1 claims2001: 9 claims2003: 1 claims2004: 1 claims2006: 1 claims2007: 2 claims2009: 1 claims2010: 4 claims2011: 5 claims2012: 1 claims2014: 10 claims2016: 1 claims2018: 1 claims2019: 21 claims2023: 1 claims2024: 21 claims19801990200020102020

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.

Full Woodbury County flood history: disasters, storm reports and events →

The zones you’ll see on the map

Cross-section of a river floodplainDiagram: a river valley. The floodway is the channel and the land beside it; the 1%-annual-chance flood surface (the base flood elevation) covers the valley floor as zone A or AE; a narrow band higher up is shaded X, the 0.2% floodplain; higher ground is X.0.2% CHANCE A YEAR (500-YEAR)BASE FLOOD ELEVATION · 1% A YEARXAEFloodwayAEX
  1. A / AE Inside the 1%-a-year floodplain: about a 26% chance of flooding over a 30-year mortgage. AE has a mapped base flood elevation; plain A does not.
  2. Floodway The channel and the land beside it that has to be kept clear enough to carry the flood. Building here is tightly limited.
  3. X shaded The 0.2% (500-year) floodplain, plus some levee-protected and very shallow flood areas.
  4. X Outside both lines. No federal requirement to insure, which is not the same as no risk.

Every flood zone code explained →

Flood insurance in Sioux City

If a building 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.

The average NFIP premium across Iowa was $1,363 a year on August 31, 2026 (premium plus the federal policy fee; the reserve fund assessment and HFIAA surcharge come on top). Risk Rating 2.0 prices each building on its own flood risk, so a quote can be far from the average.

Outside the high-risk 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. Quotes: FloodSmart.gov or a local agent.