By Keith Coffman
BOULDER, Colo. (Reuters) - Torrential downpours unleashed flash flooding in Colorado that killed at least three people and forced thousands to flee to higher ground as rising water toppled buildings and stranded motorists in their cars, officials said on Thursday.
The unusually heavy late-summer rains drenched Colorado's biggest urban centers, stretching 130 miles along the eastern slopes of the Rockies from Fort Collins near the Wyoming border south through Boulder, Denver and Colorado Springs.
The city of Boulder and a string of other towns nestled along the so-called Front Range of the Rockies north of Denver were especially vulnerable as floodwaters cascading down rain-soaked mountainsides spilled through canyons that funneled the runoff into populated areas below.
"There is water everywhere," said Andrew Barth, the emergency management spokesman in Boulder County. "We've had several structural collapses. There's mud and muck and debris everywhere. Cars are stranded all over the place."
Heavy summer rains known as monsoons are not unusual for Colorado, but the intensity and duration of this week's downpour was extraordinary, especially this late in the season, said Kari Bowen, a Weather Service meteorologist in Boulder.
The latest deluge began on Monday night with steady rains that persisted through Wednesday and grew heavier overnight.
"The street was like a river, and I knew it was time to go," said Kitty Kintzing, 65, an artist who fled her ground-floor apartment at the mouth of Boulder Canyon on Thursday morning and took shelter at an American Red Cross facility in town.
"I've never seen anything like this," said Kintzing, who has lived in Boulder, a city of roughly 97,000 people northwest of Denver, since 1969.
Low-lying areas beyond the foothills were also susceptible. An estimated 2,000 to 3,000 people were ordered evacuated from their homes in Commerce City, a blue-collar suburb just north of Denver, when a retaining pond there overflowed and flooded surrounding streets, city police said.
Additional evacuations might be necessary due to a separate dam breach at a retaining pond in the nearby Rocky Mountain Arsenal National Wildlife Refuge, police spokesman Christian Rasmussen said.
On the east side of Denver, police issued a voluntary evacuation alert for a neighborhood of about 200 people when a retaining pond in the adjacent town of Aurora overflowed, flooding several homes, Denver police spokesman Sonny Jackson said.
But some of the heaviest precipitation was recorded in Boulder, where at least 9-1/2 inches of rain had fallen by Thursday afternoon, with higher amounts in the foothills west of town, Bowen said. Boulder typically averages just an inch and a half of rainfall for all of September, she said.
WARNING BY LOUDSPEAKER
The rains transformed Boulder Creek, which runs through the heart of the city and the University of Colorado's Boulder campus, into a raging torrent that spilled over its banks and flooded adjacent parking lots and streets.
Water gushed over sidewalks, roads and bike paths throughout the downtown area as sirens wailed and public-address loudspeakers urged residents to stay clear of high water.
"Warning: Flash flood. Please proceed to higher ground. Do not cross standing or running water. Do not cross Boulder Creek," residents were warned.
The university campus was closed for the day, as were Boulder-area public schools and all municipal office buildings.
More than 400 students were evacuated from ground-floor campus housing overnight, campus police spokesman Ryan Huff said. Red Cross spokesman Chip Frye said two large nursing homes in town were also evacuated.
"It's really something here. I tell you, I've never seen rain like this. It's endless," said Boulder resident Lauren Sundstrom, 48, who began moving belongings out of her basement on Thursday as water began creeping in.
Barth, the Boulder County emergency management spokesman, said that up to 4 more inches of rain was expected to fall in the area on Thursday before tapering off.
Roads across the region were flooded, and standing water throughout Denver snarled the morning rush-hour commute.
All 200 residents of Jamestown, just north of Boulder, were forced to flee overnight, while the town of Lyons, further to the north, was cut off as floodwaters washed out U.S. Route 36 linking Lyons to Boulder, county Sheriff Joe Pelle said.
He said Lyons had reported that residents had no fresh running water and its sewage treatment plant had been knocked out. "We're trying desperately to get to them," Pelle said.
At least two people died in flooding in Boulder County, one whose body was found in a collapsed building in the Jamestown area and another who drowned elsewhere in the county, Commander Heidi Prentup of the Boulder County Sheriff's Office said.
The body of a third victim, a man, was found by police on flood-watch patrols in Colorado Springs, about 100 miles to the south, officials said.
Pelle said it was possible that more flood-related fatalities could emerge as emergency crews reached areas cut off by high water.
Heavy rains also breached an earthen dam on Meadow Lake in a remote corner of Larimer County north of Boulder, sheriff's spokeswoman Jennifer Hillman said. Nearby homeowners were warned by telephone of possible flooding, but the dam release dissipated without causing injuries or major damage.
(Writing by Steve Gorman; Additional reporting by Alex Dobuzinskis; Editing by Cynthia Johnston, Grant McCool, James Dalgleish and Diane Craft)