Natural hazards · Big Sioux

Big Sioux, SD natural hazards

Most of the natural-hazard damage FEMA expects in Big Sioux comes from inland flooding, and overall the risk is very high for a U.S. community. Flood insurance has paid 27 claims here since 2011.

FEMA National Risk Index, December 2025 · OpenFEMA claims, aid & declarations

Expected damage

How exposed is Big Sioux?

Very high

vs. U.S. communities

FEMA expects yearly storm and flood damage to homes and buildings in Big Sioux to be higher than in 86% of U.S. communities, mostly from inland flooding and tornadoes.

Inland flooding67%Tornadoes18%Everything else16%

By hazard

What Big Sioux faces

Each hazard’s share of the damage FEMA expects here, and how that compares with the rest of the country.

Inland flooding

67% of expected damage

Well above average · higher than 94% of U.S. places

Recorded about 4 times a year in the area

Tornadoes

18% of expected damage

Well above average · among the top 1% of U.S. places

Lower here

HailIce stormsWinter weatherCold wavesHeat wavesWildfireEarthquakesLandslidesStrong windLightningDrought

Not a risk here

Coastal floodingHurricanesAvalanchesTsunamisVolcanic activity

Flood risk changes street by street. Check a specific address on FEMA’s flood map, and ask about flood insurance before you buy.

Flood insurance claims

Does Big Sioux flood?

Every paid claim on a federal flood insurance policy in Big Sioux, from FEMA’s records.

27paid claims since 2011

$1.1Mpaid to owners

0homes flooded more than once

20112026

Biggest named events

Late spring storms: 19 claims, $782K
June Midwest Flooding: 3 claims, $260K

of homes in flood zones
are insured

of all homes
are insured

No community discount. Big Sioux isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.

Insurance rates: Union County.

Disasters that hit Big Sioux

Federal disasters declared here

None of the disasters declared for Union County shows FEMA aid or repair money reaching Big Sioux itself in FEMA’s records.

Brought FEMA money into Big SiouxDeclared for Union County only

Union County has had 15 natural disasters declared since 1953, most often floods and severe storms.

Around Big Sioux

Big Sioux and the towns around it

Very lowLowModerateHighVery high

Big Siouxmostly inland floodingVery high

Dakota Dunesmostly inland floodingVery high

North Sioux Citymostly inland floodingVery high

Jeffersonmostly inland floodingVery high

Sioux Citymostly tornadoesModerate

About these numbers

How to read this page

An average, not a forecastFEMA’s National Risk Index estimates the damage 18 kinds of natural hazards cause in a typical year, from decades of records and models. A quiet decade can follow a bad year.

Compared by rate“Higher than N%” compares yearly damage as a share of what’s here, so a big city isn’t rated riskier just for having more buildings. Big Sioux covers 1 census tract, combined by population.

Money that reached townFlood claims are matched to Big Sioux’s own flood-insurance community (here, the census tracts inside it); household aid to the registrant’s city; repair grants to the Township of Big Sioux. FEMA’s model follows property values, so a place that recently lost many homes can rate lower than it feels.

FEMA’s expected losses across Big Sioux total about $5.7M a year, counting buildings, people and crops.

Sources: FEMA National Risk Index (December 2025); 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. Census tracts: U.S. Census Bureau.