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FEMA flood zones · Idaho

Twin Falls County, Idaho Flood Zone Map

16 flood insurance claims·$24,809 paid·1 federal flood & hurricane disasters

Less than 1% of Twin Falls County’s area is in FEMA’s high-risk flood zones.

Share of the whole county outline, rivers and lakes included; parts FEMA hasn’t mapped count as zero.

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 Twin Falls County, Idaho. 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.

How deep the water got

outlet80″ door12″24″36″48″60″72″84″

In flood insurance claims here that reported a flood depth, the average was 16 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.

Flood claims, year by year

The worst year was 1979, with 4 claims and $4,696 paid.

1979: 4 claims1989: 1 claims1993: 2 claims1999: 1 claims2005: 1 claims2014: 2 claims2017: 2 claims2021: 1 claims2024: 2 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.

Federal disasters

4 federal disaster declarations since 2005, 1 of them floods, coastal storms or hurricanes.

DisasterBegan
Severe Winter Storms And FloodingFeb 5, 2017
Hurricane KatrinaAug 29, 2005

Weather and water disasters only; most recent first. Source: OpenFEMA Disaster Declarations.

Recorded flood events

11 since 1996: 8 flash floods and 3 river or area floods.

EventDateDamage
FloodFeb 8, 2017$2.5M
Flash FloodAug 13, 2014—
Flash FloodSep 4, 2013—
Flash FloodAug 5, 2010—
Flash FloodJul 5, 2009—
Flash FloodJul 25, 2006—
Flash FloodJun 8, 2006—
FloodJun 1, 1997$50.0M

— = no damage estimate in the record. Source: NOAA Storm Events Database.

From the storm reports

Flood · Feb 8, 2017. Strong Southwesterly flow behind a warm front spread heavy rain across most of the intermountain west. Flooding occurred in most of South Central Idaho.

Flash Flood · Aug 13, 2014. An upper level low pressure system off the coast of Oregon moved slowly inland on the 13th leading to more severe weather across Southwest Idaho.

Flash Flood · Sep 4, 2013. Moist flow and increasing winds across the Intermountain West ahead of an upper low situated off the coast of Washington helped to create conditions for severe thunderstorms across parts of Southeast Idaho on the 4th of the month.

Flash Flood · Aug 5, 2010. An area of strong thunderstorms developed over the West Central Mountains of Idaho and downed trees along an approximately 50 mile path.

National Weather Service narratives, lightly trimmed. Source: NOAA Storm Events Database.

The zones you’ll see on the map

Every colour on the map above is a place on this drawing: where the ground sits relative to the flood FEMA plans for.

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 Twin Falls County

If a building in Twin Falls 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.