Short answer: Montana's Department of Natural Resources and Conservation explains that a 1% annual chance (100-year) floodplain is a high-risk Special Flood Hazard Area, and the floodway inside it must be kept free of new development so the base flood can pass. DNRC warns that levees and roads or railroad embankments reduce but don't remove risk, and it runs new flood studies on watersheds such as the Milk River and the Yellowstone basins.
This guide is general information for Montana property owners and renters about flood risk and the National Flood Insurance Program. It isn't a coverage determination. FEMA maps, your community's floodplain ordinance and your policy wording control.
Floodplain versus floodway
DNRC's landowner page separates two ideas:
- The 100-year (1% annual chance) floodplain is a high-risk Special Flood Hazard Area. Newer maps label these A, AE, AO or AH zones; low and moderate risk show as X and shaded X.
- The floodway is the part of that floodplain that must be kept free from new development so the base flood can pass without substantially raising flood heights. It usually sees the fastest, deepest water.
DNRC adds that there is no "no-risk zone"—everyone has some flood risk.
Levees, roads and embankments
DNRC is blunt: levees may reduce risk but don't eliminate it, can deteriorate, and can be overtopped or breached. Most roads, railroad grades and other embankments were not designed as levees; to be shown as reducing risk on a map, a structure must meet FEMA engineering standards with certified documentation. DNRC also points to channel migration zone mapping, since Montana rivers move laterally over time.
New flood studies
DNRC's Floodplain Mapping Projects page lists studies underway—examples include the Madison–Ruby–Jefferson watersheds, Milk River watershed, Missoula–Granite, and the Upper, Mid and Lower Yellowstone basins. If your county is in one, compare the draft and effective maps before you renew.
Coverage
To check a property, DNRC sends you to FEMA's National Flood Hazard Layer or Map Service Center. Its own advice: "The best way to protect yourself is to buy flood insurance." Quote NFIP through FloodSmart; most new policies wait 30 days.
Questions? Contact Alishahi Insurance or call (877) 711-4545. See insurance in Montana.
Frequently asked questions
What's the difference between the floodplain and the floodway in Montana?
The floodway is the part of the 1% annual chance floodplain kept free of new development so the base flood can pass; it usually has the deepest, fastest water.
Does a levee or road embankment protect a Montana property from flooding?
DNRC says levees may reduce risk but don't remove it, and most roads and embankments weren't built as levees.
Where do I check a Montana property's flood zone?
DNRC points to FEMA's National Flood Hazard Layer or Map Service Center.
Alishahi Insurance · 439 N Canon Dr, Penthouse, Beverly Hills, CA 90210 · (877) 711-4545 · CA License #4348151. General information only. This isn't legal, tax or financial advice or a coverage determination. Coverage depends on policy language and underwriting, and rules vary by state.