BOULDER, Colo. — Clancy Philipsborn stood on the banks of Boulder Creek examining the flood-level marker he helped erect. The 18-foot stone and glass tower was a bit damaged but still standing.
"This piece of granite broke off," he said, running his hand over the line of sediment left on the monument by the historic floods that have swept through Colorado. He pointed to small boulders and uprooted trees littering the creek that runs through the center of this university town. "These weren't here last week."
Like communities up and down the Front Range, Boulder has long been known to be at high risk for flooding because it sits at the mouth of a canyon and is threaded with creeks. And officials here prepared for the inevitable. The city bought and removed buildings from flood-prone areas, built automatic floodgates around its creek-side municipal building and raised bridges to accommodate surging water and tumbling debris.
When epic rains soaked this city with more than 15 inches in just a few days, the planning seemed to pay off. While there was significant property damage, the city fared better than some neighboring communities ravaged by floodwaters. Not a single bridge in Boulder was destroyed.
The flood marker was put in place two years ago to show the expected water level in a 50-year flood, a 100-year flood and one comparable to the worst in local memory: the Big Thompson flash flood of 1976 that killed 144 people in a canyon to the north. It is also a memorial to Gilbert White, the late University of Colorado professor known as the "father of flood plain management," who believed that people should move structures out of flood-prone areas instead of relying on dams and levees.
"We know it floods. We know it's going to flood again," said Philipsborn, a retired disaster management consultant and former student of White's. "We weren't sitting here with our heads in the sand saying, 'Whoa, where did that come from?'"
What hardly anyone anticipated was so much rain for so long, over so wide a swath that everywhere flooded at once.
A record 17.15 inches of rain fell along the Front Range in about a week, nearly as much as the area usually gets in a year. The rain was so intense over a two-day period in some areas that meteorologists say it was a 1-in-1,000-year event, and the often stodgy National Weather Service described it as "biblical."
"This was really off the charts," said Matt Kelsch, a meteorologist at the University Corp. for Atmospheric Research here. "When you set records, usually you go up by a degree or by a half-inch. In this case, we just blasted past the old records."
Instead of a single canyon's catastrophic flash flood, Colorado suffered a widespread disaster: Water surged across 17 counties and into Nebraska, killing at least seven people, destroying at least 1,800 homes and damaging more than 16,000 others as of Friday morning. The flooding caused sewage and oil spills and demolished roads and bridges. Hardest hit were northern Boulder County and Larimer County, where the rain fell higher in the mountains, gathered in tributaries and picked up steam as it barreled down canyons toward the plains.
The 1976 flood was the previous benchmark for catastrophe in the steep and narrow canyons along the Front Range. So many died in their cars along Big Thompson Canyon that officials later stabilized embankments, elevated the canyon's section of U.S. 34 and put up signs urging people to climb to higher ground in case of flooding.
Kelsch has taken people on field trips showing them how that highway was rebuilt and asking, "If a big flood came through again, would this be enough?"
It wasn't, it turns out. The highway was clobbered again, and is expected to take months to repair.
One of those cut off from her home is Barb Anderson, a 37-year resident of Big Thompson Canyon who survived the 1976 flood. This time, from her home perched safely above the river, she found herself once again watching the rain pour down and the river spill out of its banks. She was able to get out by catching a ride on an ATV, but officials told her it would be at least six months before she could move back. "We just can't get to our house," said Anderson, 74, who is renting a home in nearby Loveland.
Marlene Johnson of Highlands Ranch, whose mother drowned in the 1976 flood, said she had thought it was a once-in-a-lifetime disaster. "I didn't ever think I would see the Big Thompson flood again like it did in '76," she said. "But here it is."
In Boulder, as residents worked to remove debris and dry out their homes, students and academics packed a University of Colorado lecture hall last week to try to understand this disaster. Geography professor John Pitlick had unsettling news: The level of inundation in Boulder was in line with a 50-year flood or less, not greater.
In an interview, Pitlick said what happened was not too different from the intense bouts of rain that have hit the San Gabriel Mountains, unleashing monster flows of debris. He grew up in Pasadena and has studied the effects of floods in both states. "This flood threat exists all up and down the Front Range, so the same kind of thing could happen anywhere," he said. "And it did."
Boulder has spent about $45 million on flood projects since 1997, including floodgates, culverts, underpasses, stream bank restoration and storm sewer improvements. That's perhaps one reason the city did not see as much destruction as nearby Lyons, where converging creeks, the North and South St. Vrain, took out bridges, municipal buildings and homes.
But Boulder Creek's flows reached only about 5,000 cubic feet per second, falling short enough of the 100-year flood rate of 12,000 cubic feet per second that the municipal building's automatic floodgates did not activate, said Nick Grossman, a spokesman for the city's Public Works Department.
At a City Council meeting last week, officials said Boulder fared much better than it could have. City Manager Jane Brautigam credited that, in part, to "years of investment to mitigate floodwaters."
On the agenda before the rain, and now eerily relevant, was an ordinance to require new flood-proofing measures for crucial facilities in the city's flood plain, including day-care centers, senior homes, fire stations and sewage plants. It's on track to be approved next year.Copyright © 2015, The Baltimore Sun