Walls of water cascading down hillsides caused flash floods across Colorado on Thursday, killing at least three people. The flooding cut off major highways, isolated mountain towns and closed the main campus of the University of Colorado, the authorities said.
“This is not your ordinary disaster,” said Joe Pelle, the sheriff of Boulder County, where two of the deaths were reported.
Longmont's city manager declared a state of emergency Thursday morning as the rapidly rising St. Vrain River and Left Hand Creek effectively cut the city in two.
The rising waters, declared a "500-year flood" by city officials, forced neighborhoods to evacuate and major streets to close,
As heavy rain continued falling late Thursday, homes, bridges and small dams built along the mountains that bisect the state collapsed, succumbing to rushing floodwaters and record levels of rainfall. Mudslides swept down hillsides left treeless by recent wildfires. Firefighters made dozens of rescues as cars were overtaken by rain-swollen creeks and roads suddenly gave way.
Boulder County was hit hardest, with up to 6 inches of rain falling over 12 hours. But flooding was reported all along the Front Range, from Colorado Springs to north of Fort Collins.
Capt. John Burt of the Colorado State Patrol said a storm cell moved over the mountains during the night, headed east over the Plains, then circled back around. The National Weather Service warned of an "extremely dangerous and life-threatening situation" throughout the region as the flooding forced people from their homes and caused mud and rockslides in some areas.
"Move to higher ground now. Act quickly to protect your life," the Weather Service warned throughout the morning.
Boulder Office of Emergency Management spokeswoman Gabrielle Boerkircher said many roads were blocked and volunteers were trying to help stranded people until emergency crews could arrive.
Boerkircher told The Associated Press one person was killed when a structure collapsed in the tiny town of Jamestown. Boulder County Sheriff Joe Pelle said another person was also found dead in northern Boulder.
"We're trying to get to Jamestown," Boerkircher said of a mountain community northwest of Boulder. "A lot of towns need assistance, and we cannot get through."
Two other structures in the area were also damaged and may have collapsed.
To the south, Colorado Springs spokeswoman Kim Melchor said police conducting flood patrols found a body in Fountain Creek on the west side of the city early Thursday.
National Weather Service meteorologist Bob Kleyla said a 20-foot wall of water was reported in Left Hand Canyon north of Boulder, and a firefighter radioed he was trapped in a tree. He said rescuers were trying to get through, but were blocked by debris.
In Broomfield, U.S. Highway 287 collapsed when a culvert washed out, dumping three vehicles into the rushing water. Three people were rescued and had minor injuries.
Near Lyons, about 2 feet of water was standing on U.S. Highway 36 as a normally shallow creek known for trout fishing flooded its banks.
At least one earthen dam gave way southeast of Estes Park, the gateway to Rocky Mountain National Park, and water levels could rise downstream as authorities release more water to keep more dams from giving way.
A National Guard helicopter requested to help pull people from their homes hasn't been able to take off because of fog and low cloud cover throughout the area.
Flash flood warnings were issued for multiple counties in the region, including Jamestown and the Fourmile wildfire burn area.
Flash flood emergencies were also issued downstream from the Front Range mountain areas, including Fort Lupton, Dacono, Plateville and other farming areas as debris piled up near bridges.
An evacuation center for the mountain residents has been sent up in nearby Nederland, officials said.
Meanwhile, about 400 students in a dorm at the University of Colorado in Boulder were evacuated and classes were canceled Thursday and Friday because of the flooding.
Mudslides and rockslides were reported in several areas, with parts of U.S. 6, Boulder Canyon, Colorado 14 and U.S. 287 all reporting problems and temporary blockages during the evening Lefthand Canyon was reported blocked by one of the many slides.
Boulder police dispatchers were receiving calls of flooded homes and streets and submerged cars.
One volunteer fire crew was stranded on a mountainside after a wave of rainwater abruptly washed out a road, the authorities said.
Much of the worst of the flooding Thursday appeared to be in Boulder, where the university canceled classes Thursday and Friday and some 500 students and staff members were ordered evacuated. Dozens of buildings have been damaged, the university said, including the school’s theater and the Norlin Library.
A message posted on the university’s Web site Thursday announced: “Wall of water coming down Boulder Canyon. STAY AWAY FROM BOULDER CREEK.”
But the warning did not dissuade some people from flocking there. They stood on bridges marveling at the torrent of fast-moving brown water as it swept away anything in its path.
“I’ve never seen anything like this,” said Ryan Corbett, 24, a student who was among the onlookers. “I’ve lived here for seven years. This is unreal.”
A few miles north, a 50-yard wide portion of Route 36 was submerged as a stream bed overflowed and coursed by at 1,000 cubic feet per second, said Anne Reid, a firefighter with the Lefthand Fire Protection District.
“This is usually just a little stream that you wouldn’t even think to fish in,” Ms. Reid said.
The flooded highway has cut off residential areas for the foreseeable future, sweeping up whole willow and cottonwood trees as if they were twigs. John and Billie Brumder, who live across from the Crestview Estates neighborhood, said they were awakened at about 1:30 a.m. Thursday by the frightening sound of large rocks being dragged along the creek bed.
“When I heard that, I knew it was a big deal,” he said. “I knew we had to get out of there.”
Their car, which was already partly submerged, stalled, Mr. Brumder said, but they were able to escape in their pickup truck.
The authorities said Thursday afternoon that they expected the death toll in the state, currently at three, to rise.
One person drowned and a second person was killed when a structure collapsed in the town of Jamestown, northwest of Boulder. The third victim was found in Colorado Springs by police officers conducting flood patrols.
Rain had been falling in the Boulder area since Monday, but picked up significantly on Wednesday evening, causing mudslides in Colorado’s Front Range, where since 2010 wildfires have denuded some areas of trees and brush that would have normally helped soak up the moisture.
Dozens of streams and creeks overflowed, and downstream, portions of Colorado Springs and Denver flooded, as well as large parts of Boulder. The National Weather Service reported that more than 6 inches of rain had fallen in a 12-hour period. Forecasters predicted that the rain would continue into Friday.
According to provisional data from the United States Geological Survey, parts of Boulder Creek reached flood levels that have a 1 in 100 chance of occurring in any given year — what some refer to as a 100-year flood.
Sylvia Tawse, who owns a vegetable and flower farm in Longmont, said her husband got a call at 3 a.m. from the local fire chief, warning that a 20-foot wall of water was barreling down nearby Left Hand Creek. Ms. Tawse’s property, nestled among a patchwork of family farms about 10 miles north of Boulder, was spared. But her neighbors were not so lucky.
“We’re on slightly higher ground, so we’re not in danger,” she said. “But their farm fields are completely underwater.”
Ms. Tawse said that by early Thursday, Left Hand Creek, typically barely a trickle, had swollen into a raging rush of muddy water.
“We had a bad flood here in 1995,” she said. “But this is worse than that.”