Floodplain Mapping Update: Clark Fork River, Bitterroot River, Rock Creek

Let us know your questions on the updated floodplain maps for Rock Creek and the Clark Fork and Bitterroot rivers.

Missoula County is working with the Federal Emergency Management Agency (FEMA) and the state Department of Natural Resources and Conservation (DNRC) to update floodplain maps for the Clark Fork River, the Bitterroot River and Rock Creek. The floodplain and rivers are natural systems that change over time, and the new maps are intended to provide more reliable and detailed information about areas prone to flood hazards. Updated floodplain maps will depict the latest, most accurate flood risk data, and will eventually replace the existing floodplain maps, which are based on data from the 1970s.

Following a public engagement period, Missoula County will need to adopt the updated maps for residents in the floodplain to be eligible to buy flood insurance through the National Floodplain Insurance Program. Residents will not be eligible for this program if the County does not adopt the updated maps. Additionally, adopting the maps ensures Missoula County is eligible to receive federal assistance in the event of a major flooding disaster. If the County does not adopt the updated maps, it wouldn't eligible for federal funds, and recovery costs would likely fall to local property taxpayers. Adopting the new maps also will ensure Missoula County bases future land-use decisions on the most accurate data.

Who will be affected?

Residents who live in near these waterways in the following areas may be affected by changes to the floodplain maps. Property owners who will potentially be affected will receive a postcard about the updated maps.

• Bonner/West Riverside
• Clinton
• East Missoula
• Frenchtown
• Lolo
• Orchard Homes

How will they be affected?

Properties that previously were not in the floodplain may now be in it, and lenders may re-evaluate policies and require homeowners with mortgages to have flood insurance. Homeowners should check with their lender or insurance agent after the maps are adopted.

After the maps are adopted, Missoula County also will require any new construction in the floodplain to apply for a floodplain permit and meet certain requirements. Examples of these requirements include elevating the structure, using flood-resistant building materials and installing flood vents. While Missoula County recommends property owners in the floodplain take mitigation measures to protect their property, they will not be required to unless they plan to alter, substantially improve or replace a structure.

What’s next?

Preliminary maps are expected to be released by FEMA in winter of 2025. Residents who may be affected by any changes will receive a postcard ahead of time. Missoula County will work with FEMA and DNRC to conduct public outreach and education on the preliminary maps, including public open houses sometime in 2025.

See Timeline for more details.