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THREE FORKS — The west side of town looks much like the rest of the city. A park surrounds rows of homes. The streets are generally quiet. A few dogs play in fenced yards.

But recently released draft maps from the Montana Department of Natural Resources and Conservation show this area would be more significantly impacted by a 100-year flood of the Jefferson River than previously thought. As a result, the city is exploring ways to limit its flood risk and is grappling with questions of safety, affordability and growth.

The draft maps place most of the homes on the west side of Three Forks in the river’s floodway, while previously they were in the broader floodplain.

The new designation means these homes are likely to suffer the fastest and deepest water during a 100-year flood.

Given the risk, no new construction is allowed in a floodway. If a building in a floodway is destroyed by a natural disaster, it cannot be rebuilt.

“We’ve always had to build within the floodplain and contend with the risk that presents, but the new maps place a significant amount of land in the floodway, which could be devastating,” said Kelly Smith, the city’s floodplain administrator.

Three Forks has never experienced a 100-year flood, which has a 1% chance of happening in any given year, so it is difficult to know the impacts such a flood would have, but the new maps are the first step toward understanding the risk and planning for it, said Nadene Wadsworth, with the DNRC.

“Flooding is the most costly and common disaster and it can occur anywhere, so having that updated accurate information will really help the community,” she said.

The placement of a property into the floodway or the broader floodplain has significant economic impacts.

Properties mapped into the floodplain and floodway are often required to have flood insurance, which can be expensive, especially in areas with as high a flood risk as the west side of Three Forks.

Property values could also decline.

A 2019 study from Landscape Economics on Pennsylvania found that properties often lose value when they are mapped into a flood zone. However, the real estate market and development pressure in Gallatin County are so strong that the effect of the draft maps on the values of homes in Three Forks might be more limited.

Development is permitted in areas of the floodplain outside the floodway, but it is often expensive because of strict regulations and the additional work, such as bringing in dirt to raise homes to a certain height, that can be required.

“We have more development coming to town and businesses looking to come in, but given how much land is added to the floodplain and the floodway with the new maps, it’s hard to say if that could change,” Smith said.

The revisions to the floodplain maps come as Three Forks is updating its growth policy, which outlines a vision for the city’s future.

The document is particularly important because Three Forks, like the rest of Gallatin County, is growing rapidly. From 1990 to 2018, the number of single-family homes increased by 46%, according to an analysis of Montana Department of Revenue data by Headwaters Economics, a Bozeman nonprofit.

Previous growth policies have identified the west side of town as the location for future homes.

In fact, the land west of Jefferson Street was annexed into Three Forks years ago with the thought that it would eventually become a logical addition to the growing city. However, the draft maps place that land in the floodway, so it cannot be developed.

“That area to the west was always thought of as the way we could grow because Three Forks is constrained by the Madison River on one side, the highway on another and the talc plant,” Smith said. “The draft maps raise a lot of questions about what the future might look like for Three Forks.”

Given the constraints the new maps place on the city, developers might be more inclined to build outside city limits.

Rural subdivisions are often more expensive for cities because homeowners still use city infrastructure and services but don’t pay city taxes. That issue is particularly complicated in Three Forks because it lies at the edge of Gallatin County, so construction outside city limits could be in other counties.

“The mapping update would negatively affect growth within city limits, stifling our economy,” Mayor Sean Gifford said. “But as we work on the growth policy, we will look at how we can continue to grow even with the new maps.”

The creation of the new maps is part of a major DNRC project.

In 2017, state officials began studying portions of the Madison, Ruby, Jefferson, Beaverhead and South Boulder rivers and Mill and Indian creeks to improve the decades-old floodplain maps for some of southwest Montana.

This fall, DNRC released draft maps based on the study, which included high-accuracy topographic information and updated hydrological data.

While conducting the study, DNRC engineers discovered ways Three Forks could reduce its flood risk and presented those findings to city officials.

At about the same time, Headwaters Economics was launching its new flood program. The nonprofit reached out to state officials to see if any Montana towns needed flood assistance and was put in touch with Three Forks, said Kristin Smith, with Headwaters Economics.

Headwaters, city officials and Great West Engineering built on DNRC’s work to develop a flood mitigation project that would likely remove as many as 90% of the structures from the Jefferson River’s 100-year floodplain.

Three Forks is now hoping to construct a channel and culvert that would direct overflow of the Jefferson west of Three Forks before returning the water to the river. The building of the channel and culvert would also allow for the creation of a recreation pond near U.S. Highway 2 between Front and Sabena roads, about one mile west of town.

The project would cost $5.04 million. Three Forks, with assistance from Headwaters Economics, has applied for a FEMA grant that would cover 75% — or $3.78 million — and the city would contribute 25% — or $1.26 million.

“The new draft maps introduce a lot of uncertainty into how Three Forks will grow, and I think part of the goal of the mitigation project is to help the community grow in the way it wants to grow and to reduce that uncertainty,” Smith said.

It could take months before the city knows whether it will receive the FEMA grant. Even if the city is awarded the grant, the project might not go forward if the city is unable to purchase easements required for the construction from private property owners or if it is unable to come up with its share of the costs.

Because of the uncertainty, Headwaters is working with the city to explore other options, Smith said.

Over the last few months, DNRC has been presenting the draft maps to Three Forks residents and is setting up meetings for affected landowners in other places, including Ennis and Twin Bridges.

DNRC has also provided its draft maps to the Federal Emergency Management Agency, which will use them to update its official floodplain maps.

FEMA is expected to publish official draft maps later this year. FEMA will then hold a formal public comment and appeal period before the official draft maps are finalized, likely in 2022 or 2023.

As state and federal officials complete the mapping update, Three Forks home and business owners are beginning to understand how a major flood could impact them and the city.

Chuck Wambeke, a business owner involved with the Three Forks Chamber of Commerce and the growth policy update, said he’s worried about what the new maps could mean for Three Forks.

“Right now, our growth is hampered by the floodplain, and with the new maps, it will be even worse,” he said. “Our city can’t grow within the city limits because the whole city is essentially in the floodplain and the cost of the development regulations is untenable.”

He said the only path forward for Three Forks is building the channel and culvert for the Jefferson River.

“If the new maps are approved without the mitigation project, it is basically condemning all of this property around town,” he said. “With the mitigation project, we can grow here in Three Forks and continue to invest in our community.”

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Perrin Stein can be reached at pstein@dailychronicle.com or at 582-2648.

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