Rising rivers don’t necessarily follow the lines on a map

June’s record-breaking flooding in Montana illustrates the importance of risk mapping for people living in the floodplain.

As the Yellowstone River rose in June, sandbag walls sprouted like Lego sets, buffering properties around the city of Livingston, Montana, population about 8,000. People moved valuables into their cars, ready to hit the road. Hundreds of structures in town were evacuated, including my house, which is located in a so-called “500-year floodplain” — a zone with a .2% annual risk of flooding. The high, muddy water caused millions of dollars of damage in the region. 

Waiting out the flood at a friend’s place on higher ground, uncertain about the fate of my own home, the map lines that inform how officials think about flood risk abruptly became tangible to me. For most people, floodplain maps are difficult to find and even tougher to understand. The city’s official map — a hodgepodge of smudges, lines and blots — is like a Rorschach test: It may convey very different meanings to homeowners, developers, politicians and scientists, and this can have lasting consequences for how communities cope with floods. Real risk, I learned, doesn’t always follow the lines on a map.


IN THE EARLY 2000s, the Federal Emergency Management Agency began revamping its flood maps. Those maps detail risk — where homes and property across the country fall within the “100-year floodplain,” for example, where there are usually special requirements for development, and owners must purchase flood insurance. They also delineate the “regulatory floodway,” areas at even higher risk of water rushing through, where development is in many cases prohibited.

When the agency presented a study by the U.S. Army Corps of Engineers to the city of Livingston, it showed that hundreds of homes were at high risk of flooding, potentially adding a hefty price tag for anyone thinking of buying a home or developing there. According to city commission minutes, local newspapers and official documents, locals and city officials were incensed and started to push back immediately.

A makeshift levee, first built in the 1930s and bolstered over the years, ran through town along the Yellowstone River to protect property from floodwater. However, since the levee wasn’t officially certified by the U.S. Army Corps — a lengthy and expensive process — the map makers acted as if it didn’t exist at all. “The city commissioners were very concerned,” former Livingston City Manager Ed Meece told The Billings Gazette at the time. “The Corps study was grossly inaccurate and flawed.” Meece didn’t respond to multiple requests for an interview for this story.

Muddy water begins to trickle over the makeshift levee built to protect Livingston from catastrophic flooding. Nick Mott/High Country News

The situation quickly became political. Montana’s U.S. senators at the time — both Democrats — wrote to FEMA, urging the agency to “right this wrong” and expedite the mapping process. The city hired a private contractor to do an independent analysis and draw a new map. The contractor’s report contradicted the Army Corps’ results, and, as Meece told local newspapers, the remapping — a $270,000 effort — ultimately left the city with a floodplain 95% smaller than what appeared on the original map. That meant that hundreds of properties wouldn’t need flood insurance and other requirements that come with living in areas at high risk of flooding.

FEMA officially adopted Livingston’s new map in 2011.

Livingston’s floodplain map shows areas in the 500-year floodplain, pictured in orange, and parts of town in the “100-year floodplain” and “regulatory floodway,” pictured in light blue and blue-and-red stripes. The map came to be after years of back-and-forth with FEMA and a quarter-million-dollar independent study that limited the size of at-risk areas in town.
Nick Mott / High Country News

FLOODS ARE ALREADY the most common and destructive natural hazard in the country. FEMA predicts that, due to climate change, the area at risk of a 100-year flood from rivers in the U.S. will grow by about 45% by 2100. The problem is even worse in coastal areas. According to some studies, as many as 41 million Americans live in places with a 1% chance of annual flooding. That may sound small, but over the course of a 30-year mortgage, those odds stack up to about 1-in-4.

Sarah Pralle, an associate professor of political science at Syracuse University, studies the politics of how floodplain maps get drawn. She said that when the National Flood Insurance Program began in 1968, it was meant to discourage people from living in flood-prone areas by making it pricier to live there, as well as to help them recover when floods do occur by providing insurance for at-risk properties. The backbone of the program, she said, is accurate, scientific mapping. 

While Pralle wasn’t familiar with the case of Livingston in particular, she said the politicization of floodplain mapping is common. And when flood maps are challenged, it’s nearly always in the direction of making the floodplain smaller, not bigger. In a 2014 investigation, NBC News found more than 500 instances where FEMA had remapped waterfront properties — often high-end, luxury developments — into a lower-risk category. A smaller regulated floodplain means fewer people shelling out thousands a year for insurance, easier ground-breaking for developers, and a good look for local politicians. “It’s kind of human nature not to want to pay for something if you think you aren't going to need it,” Pralle said.

“It’s kind of human nature not to want to pay for something if you think you aren’t going to need it.”

That echoed my experience. There’s no requirement where I live, so I hadn’t given flood insurance a second thought since moving into my house. When the floodwaters came, I cursed my own short-sightedness. In the end, we were lucky; our home stayed dry. A few blocks away, though, our friend Celeste Mascari — also mapped in the same “500-year floodplain” — was less fortunate. Water damage left her home unlivable, and she had no insurance to help with the costs of rebuilding. As of 2020, only about 3% of the homes in Park, Carbon and Stillwater counties — which bore the brunt of the June flood’s impacts — are insured against floods.

Bubbling up from groundwater below and coming from the Yellowstone River nearby, sandbag barricades weren’t enough to hold back water from Celeste Mascari’s property. Her home and the Montessori school she runs on her property both suffered significant damage.
Nick Mott / High Country News

Pralle said that local conversations around flood maps usually focus on the cost of building and insurance. “No one really steps in to say, this is about something bigger,” she said. “This is about planning for the future.”

IN A CITY HALL CONFERENCE ROOM about two months after the flood, Jim Woodhull, the director of building and planning for the city of Livingston, unfolded a gray-and-black version of the city’s floodplain map. Woodhull, a lifelong Livingston resident, has worked for the city for nearly three decades.

These days, he said, “we don’t do a lot of floodplain regulation because there’s not a lot of floodplain mapped in the city.” He said he didn’t remember many details about the conflict between the city and FEMA, but noted that the narrow 100-year floodplain in the 2011 map has been good for the local economy. “There's been a lot of re-development and a lot of investment in properties that wasn't going to happen otherwise.

“We don’t do a lot of floodplain regulation because there’s not a lot of floodplain mapped in the city.”

Back when Livingston and FEMA were at odds over the floodplain map, the city had recently annexed a swathe of agricultural land east of town. That chunk of land became a central concern in the mapping disagreements. Part of it was sited for a new county hospital, and the rest was slated for development as Livingston grew. FEMA’s map showed the property in the 100-year floodplain, where flood insurance and strict development standards would be required, creating logistical and financial barriers to building. The city’s new map, commissioned by the private contractor, designated the area as part of the 500-year floodplain. There, just about anything goes.

In the decade since then, the hospital was built — despite opposition from some locals concerned about the flood risk. When the river rose in June, the hospital remained dry, but water surrounded the facility, cutting off access. Officials closed it and evacuated all patients.

Much of the land around the hospital is still undeveloped. But Woodhull doesn’t expect that to be the case for much longer, unless the federal government comes up with a new map that shows development would be too risky. “We’ve already annexed it, we’ve already zoned it,” Woodhull said. “Why not? It’s a good location.”

Floodplain maps are a snapshot of an ever-changing ecosystem, and climate change is likely to make events like June’s flooding more frequent and severe. A nonbinding growth policy adopted by the city in 2021 details a vision for how Livingston ought to expand. It briefly addresses flood risk: “Current floodplain maps don’t take into account climate change,” the document says. “This suggests that current floodplain maps are the ‘low bar’ for predicting flooding.”

The Yellowstone River’s water swells onto an area known as ‘9th Street Island’ in Livingston during June’s historic floods.
Anthony Pavkovich

Woodhull said conversations with FEMA about updating floodplain maps in the wake of the flood are likely to occur soon, though they haven’t happened yet. In July, Park County, where Livingston is located, officially asked for updated maps, a process that could take a couple years or longer.

That means that another battle over the lines on the map could be coming. But this time, as climate change impacts become immediately tangible and Park County faces unprecedented growth, the stakes will be higher than ever.

Nick Mott is an award-winning journalist and podcast producer who focuses mostly on climate, public land and the environment. He’s based in Livingston, Montana.

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