New Missoula floodplain map delayed for more research into Orchard Homes neighborhood
Completion of a new draft floodplain map for Missoula County has been delayed after state engineers said they need more information on levee protection already in place in the Orchard Homes neighborhood, according to the county's floodplain administrator.
Federal Emergency Management Agency and the state Department of Natural Resources and Conservation are currently designing a new floodplain map for Missoula County for the first time in nearly 50 years.
The new floodplain could restrict construction on hazardous land and require some residents in the 100-year flood mark to get flood insurance.
Matt Heimel, the county's floodplain administrator, said Tuesday the state originally planned to release the maps and notify affected property owners on Nov. 21, but a lingering question remains over levee protection in the Orchard Homes neighborhood that could change the map.
Heimel said the floodplain engineers had not yet considered the protective levee already in place near the neighborhood in their mapping process. The levee is maintained by the Army Corps of Engineers, but is not certified by FEMA like the levee in downtown Missoula.
"The draft maps show areas behind the levee as going into the floodway," Heimel said. "FEMA has come out with guidance saying when you have areas on the landward side ... the area does not automatically have to be treated as a floodway."
The levee could make a difference as to whether some land in the Orchard Homes neighborhood are considered part of the "floodway" or part of the "floodway fringe" area.
Floodway is the section of river where water would be the highest and most dangerous during a major flooding event. Those areas are generally left undeveloped and require a special permit for building.
The floodway fringe includes areas within the 100-year floodplain that would not be in the path of the main flow of the river and can generally be developed.
A current state-released draft floodplain map places more than a dozen houses in Orchard Homes in the floodway. That draft is available online , but is not the final draft floodplain map, which will include parcel-by-parcel detail, according to Heimel.
Creating the new floodplain is like a math problem. Engineers must consider the hydrology and river flows weighed against natural boundaries like hills, levees, roadways and other elevated features.
If the floodway is moved away from the south side of the Clark Fork River, Heimel said the floodway would likely shift north to more agricultural land.
"The base flood elevations, the flood depths, the flood velocities, how much water there is — that remains the same in the mapping," Heimel said. "It's just a matter of what area has to be designated as a floodway."
Adopting the proposed map as it stands would add roughly 660 properties to the 100-year floodplain, remove roughly 390 structures and leave 700 properties unchanged, according to the Montana Free Press .
Several residents have formed a group opposed to the changes and have asked the county to sever ties with FEMA. County officials have argued becoming uncompliant with FEMA would jeopardize millions in federal grant funds.
The city of Missoula is working on introducing the same draft map, but will work through its own public process to finalize the changes.
The actual draft map will not be released until sometime this winter, Heimel said. An exact time was not available at the Tuesday meeting.
Once the formal draft is released and the county holds public outreach meetings, residents will have a 90-day window to protest the new map, which county officials estimated will occur in summer 2025.
The map could be approved by the county in 2025, while the state and federal government might take more time to finalize the floodplain.
Griffen Smith is the local government reporter for the Missoulian.
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