Some local landowners, however, were "shocked," I read in the paper. "I've lived here 12 years and I've never seen anything like this!" one said.
I could almost hear the I-told-you-so in the hydrologist's quote later in the same story. "This was no 100-year flood," he said. "This wasn't even a 20-year flood. If they think this was a big deal, they have a surprise coming."
Sure, that landowner has been in the floodplain 12 years and everything has been hunky-dory. But in that same 12 years, a lot of neighbors have moved in, built on the floodplain and on other floodplains.
The subdivision reviews echo each other. Map-wielding experts minimize environmental dangers and tout design strategies. Hydrologists routinely warn of flood potential and groundwater depletion. Mostly, money talks. Like in most of the West, construction and real estate have been huge economic engines around here. The developments go in, people build on the floodplain. Then, when the inevitable happens, they are shocked.
"People have a really difficult time managing for cycles that occur at a rate longer than a human lifetime," says Monica Turner, professor of Wildland Ecology at the University of Wisconsin.
Turner specializes in natural disturbances, which include phenomena like flooding and wildfire. Much of her career has been spent analyzing a really big natural disturbance -- the 1988 fires in Yellowstone -- where she did her early fieldwork.
In the case of the '88 Yellowstone fires, people used the word "unprecedented" in every other paragraph, though, according to Turner, the only thing unprecedented was our experience with fires of that magnitude. Our precedent, it turns out, covered fires that peak on roughly a 20-year cycle. Turner's research suggests that in the Northern Rockies there is a 150-year cycle at work that burns millions of acres at a whack.
"Back in '88, people were busy blaming excess fuels and a let-burn policy in the park," remembers Turner. "What we've found suggests that it has nothing to do with that. It's the climate."
Early snowmelt, combined with prolonged drought, high temperatures, strong winds and late fall precipitation, produce the conditions ripe for a wildfire of the 1988 variety. A whopper. And there is nothing unprecedented about it. It's just a longer pulse than we're accustomed to measuring.
The same thing happens with people who build their homes on the bank of a river, or on a low-lying flood plain. It looks fine at the moment, beautiful views, a river coursing past. What could go wrong?
A river is no more static than a lightning-strike wildfire. It migrates back and forth across the valley, chewing away at the banks. From an aerial photograph, the river "corridor," as opposed to its current channel, reveals bank erosion, major flooding, channel shifting -- all effects that are "when" propositions, not "if."
We might get lucky. One hundred years could pass without much drama. Then again, somebody's turn could come next spring, and again the spring after that. It's a little bit like trusting your retirement savings to the luck of the casino.
Tom Olliff, who was a "seasonal park grunt" during the '88 fires, and who now occupies the post of chief researcher at Yellowstone National Park, thinks Turner is right about our limited ability to understand change at a landscape level.
"I think it comes down to the length of a career," he says. "I've had a long career at Yellowstone, 30 years or more. I feel like I've learned a lot, about fire in particular, over those decades. Sure, there are some things I'll pass on in the way of knowledge, but a lot of it will go away when I do, and the management wisdom clock will start new."
As for me, I paddle a lot of these local streams. I look at these river-hugging developments from water-level perspective. I find myself wishing for a little natural reckoning. I won't go so far as wishing a 100-year gully-washer on anyone, but an occasional wake-up call for floodplain residents, like the one that just pulsed through town, seems entirely appropriate.
And you know what? Let them be shocked. Maybe they'll think further down the road on the next go-round.
Alan Kesselheim is a contributor to Writers on the Range, a service of High Country News (hcn.org), where this editorial first appeared. He is the author of nine books and lives in Bozeman, Mont.