Flooding wreaks havoc on East Slope while Grand stays dry
September 23, 2013
While rains pummeled the Front Range for five days, things in Grand County stayed relatively mild, despite being as little as 14 miles away, as the crow flies, from some of the hardest-hit areas.
Colorado's historic storm started as a jet stream of warm air, moving from the Gulf coast, coursing north and east from Mexico. All that tropical, wet air pushed into the Rocky Mountains and began dumping rain. But the farther into the atmosphere the Continental Divide pushed it, the drier the air became, according to Matthem Kelsch, a meteorologist specializing in floods and storms at the University Corporation for Atmospheric Research in Boulder, or UCAR.
"It's like when you go hiking in the mountains, and notice the air gets cooler — the cold air can't hold moisture as well," Kelsch said. "As it's coming down the other side, it's going to get a lot drier."
The weather patterns that bring Grand County its snowpack are often the opposite. Westerly winds bring moisture from the Pacific coast, which hits the Divide and falls as snow. As the air moves up the Rockies, it dries and hits the Front Range as the infamous Chinook winds.
Still, Kelsch said the mountain barrier didn't put the West Slope completely in the clear.
"There was some danger in that there was a lot of moisture over the state," he said. "There were spots on the West Slope that got heavy rain, but (the Front Range) was the target for this particular storm."
From Monday, Sept. 9 to Sunday, Sept. 15, the storm targeted parts of Estes Park and Allenspark with about 12 inches of rain, and portions of Boulder with 15 to 20 inches of rain, according to data collected by the Community Collaborative Rain, Hail and Snow Network and mapped by the Denver Post. Meanwhile, Kremmling saw around 1.36 inches and Granby received less than an inch in the same period.
The good and the Bad of past floods
Most of the historic flooding seen in Grand County has occurred during runoff season. County and town managers had no information regarding the area's worse recorded flood, but many recalled the spring runoff of 2011. Snowpack in the Colorado River Basin reached 165 percent of average by May. Grand County's chief director of emergency management, Ray Jennings, said it was the biggest flood year he's seen in his 10 years working with the county.
"Our biggest issue with flooding events at that time was all the debris coming down, blocking bridges and culverts," Jennings said. "We had water everywhere."
Much of the debris came from falling trees killed by the bark beetle. Materials jammed up infrastructure and caused localized flooding throughout the county.
Jennings said the county learned a lot about debris mitigation during the event, and have been able to take measures preventing the same kind of blockage in later storm events. But he and his crew remained vigilant and cautious while watching recent events along the Front Range. They remained in contact with the National Weather Service, local police and partners at the Colorado Division of Emergency Management.
"Everyone communicated very well," he said. "With floods, our biggest priorities are being able to plan, mitigate and respond."
Longtime Fraser Valley resident Kirk Klancke remembers big floods prior to the 2011 spring runoff. About 30 years ago, in 1983 and 1984, the area again saw record levels of snowpack resulting in extreme flooding.
"My harrowing experience was driving through Hurd Creek to get to visit the Polks at their ranch," he recalled.
The water flowing down the dirt road rose high enough to flood his restored 1954 Chevy pickup. Klancke was able to dry and start the vehicle with enough time to get to the Polks' ranch, stay for a visit, then cautiously return back.
"But shortly after, the culverts washed out and the road was completely taken," he said. "There was no getting out to the Hurd Ranch, they were completely stranded."
Klancke recalled numerous spring flood events in the past. He'd take advantage of them with friends by fishing in washed-out parking lots and having boat races to Tabernash.
"We had fun with the flood," he said. "Mountain people seem to turn everything into an event."
But Klancke said water diversions to the Front Range are making floods less frequent.
"Denver can divert more of the spring high flows, which takes away spring high floods," he said. "But it's also taking away some of the recreation opportunities."
Spring floods sustained agriculture in western portions of the county prior to the construction of the Colorado-Big Thompson Project in the 1930s. The Colorado River used to bottleneck at Gore Canyon, flooding Kremmling fields and raising the water table. The federal government later had to aid farmers by constructing irrigation pumps once the floods stopped coming.
Klancke noted other benefits to flooding in the county, which can help clean out creeks and rivers like the Fraser, reducing turbidity. He said he's seen the Fraser River's water turn increasingly brown with each year, as more developments and parking lots add to runoff.
"All that brown settles down in the river," he said. "If we don't get big flushing flows like we used to, the river has a hard time cleaning itself out."
Still, if a big flood comes to Grand, there's no guarantee it will be completely beneficial. Planning and zoning officials have worked to enact building regulations that keep homes and businesses out of the 100-year flood plain. But as events in the Front Range have shown, raging water can be unpredictable.
"Our safety message is stay out of running water," Jennings said. "It's probably running faster than what you believe."