FEMA Flood Zones in Lewis and Clark County, Montana
FEMA has mapped 10,096 acres of Lewis and Clark County, Montana inside a Special Flood Hazard Area — the 1% annual chance floodplain, often called the 100-year floodplain. The map below shows every mapped flood zone inside the county boundary.
Lewis and Clark County, Montana at a glance
| Land in a FEMA Special Flood Hazard Area | 10,096 acres |
|---|---|
| Share of mapped land in a Special Flood Hazard Area | 0.5% |
| Share of the county with a published FEMA flood map | 99.8% |
| Largest mapped flood hazard area | Unstudied area (Zone D) — 1,944,358 acres |
| Distinct flood hazard categories mapped | 4 |
| Distinct FEMA flood zone codes mapped | 5 |
| Most widespread FEMA flood zone | Zone D — 1,944,358 acres |
| Land in the 0.2% annual chance (500-year) floodplain | 2,699 acres |
| Land in a regulatory floodway | 2,376 acres |
Lewis and Clark County, Montana is home to 75,331 residents. Land Owl's FEMA flood zone layer records the following within the county boundary — Land in a FEMA Special Flood Hazard Area: 10,096 acres. Share of mapped land in a Special Flood Hazard Area: 0.5%. Share of the county with a published FEMA flood map: 99.8%. Largest mapped flood hazard area: Unstudied area (Zone D) — 1,944,358 acres. Distinct flood hazard categories mapped: 4. Distinct FEMA flood zone codes mapped: 5. Most widespread FEMA flood zone: Zone D — 1,944,358 acres. Land in the 0.2% annual chance (500-year) floodplain: 2,699 acres. Land in a regulatory floodway: 2,376 acres. Every feature shown on the map above is clickable, and the figures on this page are derived from the same data the map renders, so they always agree. A free Land Owl account adds parcel boundaries, ownership records, soils, wetlands and topography over the same view.
Frequently asked questions
- How much of Lewis and Clark County, Montana is in a FEMA flood zone?
- Land Owl maps 10,096 acres of Lewis and Clark County, Montana inside a Special Flood Hazard Area, which is 0.5% of the land FEMA has flood-mapped in the county. That is a regulatory designation used for floodplain management and federal flood-insurance requirements — it is not a prediction that the land will flood.
- Is this flood zone map free to use?
- Yes. This map is free to view. A free Land Owl account unlocks the other data layers, parcel boundaries and ownership records.
- Where does this data come from?
- Land Owl maps flood zones from FEMA's National Flood Hazard Layer (NFHL), the digital record of the effective Flood Insurance Rate Maps. It is a screening view, not a flood determination: FEMA revises maps, 495 US counties have never had a digital FIRM published at all, and a lender or insurer will ask for the official record. Check the FEMA Map Service Center, or ask your local floodplain administrator, before you rely on a zone.
- Is land outside the flood zone safe from flooding?
- No. A Special Flood Hazard Area marks where FEMA has studied and mapped a 1% annual chance of flooding; ground outside one has a lower mapped risk, not no risk, and some of it has never been studied at all. Roughly a quarter of US flood-insurance claims come from outside high-risk zones.
- What is the difference between a 100-year and a 500-year flood zone?
- They are shorthand for annual probability, not for how often a flood happens. A 100-year flood zone has a 1% chance of flooding in any given year; a 500-year zone has a 0.2% chance. Either can flood twice in a decade — the odds reset every year.
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