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Missoula County proclaims flood emergency; prepares response for “high probability”

Crews work on an access bridge to what will become Broadway Island on the Clark Fork River in downtown Missoula on Thursday. Missoula County has issued a proclamation declaring a flood emergency, citing high probability that the river will reach flood stage in the coming weeks. (Martin Kidston/Missoula Current)

With the waters rising and a moderate snowpack waiting, Missoula County on Thursday issued a resolution for a flood emergency, citing the high potential that the Clark Fork River will at least hit minor flood stage in the weeks ahead.

Doing so allows the county to prepare its emergency operations plan and begin coordinating with agencies charged with responding if or when flooding takes place.

“This is something we do typically ahead of a flood season or fire season when we have a high degree of likelihood that it’s going to occur,” said Adriane Beck, director of Disaster and Emergency Services for Missoula County. “Now that we’re in this stage, when that river gauge and those forecasts look like (flooding) is imminent, we’ll be able to move forward.”

One year ago, a heavy snowpack and early spring runoff left several neighborhoods around the Missoula Valley inundated with water. The Clark Fork River closed in on 13 feet and remained well above the 10-foot flood stage for several weeks.

On Wednesday, the gauge above Missoula showed the river at 6.7 feet.

“What we saw in 2018 was the previous flood stage of 10 feet was insufficient,” Beck said. “We were starting to see negative flood impacts around homes and on streets well below that 10-foot mark. We didn’t see water come out of that (Orchard Homes) neighborhood until around 8 feet.”

After consulting with the National Weather Service, the minor flood stage on the Clark Fork above Missoula was lowered to 7.5 feet. And while this year’s snowpack is about average, history and the region’s changing climate suggests 7.5 feet will become a common occurrence.

“Looking at this gauge’s history, the 7.5-foot mark is something we see very routinely,” Beck said. “When we hit our traditional spring runoff, that’s when we look at this gauge and how often we hit that 7.5-foot mark. It’s at least an every-other-year event.”

Using several models that consider snowpack, history and potential, the current scenario suggests a high probability that the Clark Fork will top 7.5 feet in April or May.

“When you look at where our confidence level is that we’ll reach that 7.5-foot flood stage, we’re looking at that being between an 80 to 90 percent chance that it’s going to occur, based upon the conditions today,” Beck said. “It’s just a snapshot in time, but it’s a pretty high degree of confidence that we’ll hit that 7.5-foot mark.”

The county is coordinating with volunteer organizations to ensure sandbags are available. A public meeting is set for April 24 at 6 p.m. at Hawthorne School to apprise residents in low-lying areas of the current conditions.

“This (proclamation) allows us to start pulling in all those agencies that have a role to play in flooding, and it allows us to start documenting all our efforts toward flooding, so in the event we’re in a position to recoup those costs, we have good documentation,” Beck said.