Updated: July 4, 2012 at 12:00 am
The rain that many in Colorado Springs prayed for in June could soon arrive, brought by the mid-summer monsoon storms.
Be careful what you wish for. You just might get it.
Officials warn that strong thunderstorms over the foothills could bring a second disaster to Colorado Springs: flash floods caused by rain falling on now-bare hillsides.
“Once the rain hits the areas that burned hotly, those soils will not be enough to absorb any of the moisture. It will mix with the ash and cause these mud and ash flows. And they can be quite dramatic,” said Kathy Torgerson, meteorologist with the National Weather Service in Pueblo.
“If you can look uphill from you and see a burnt-out area, you are at risk.”
July and August are Colorado Springs’ wettest months, with an average of 2.84 and 3.34 inches of rain respectively, most of which falls in often-furious afternoon storms. A flash-flood watch was in effect for much of Wednesday, though the feared – or hoped-for – rain did not come .
On a burn scar the size of the Waldo Canyon fire, it may take only a half-inch in an hour for damaging runoff, mixed with ash, mud and debris, to roll into neighborhoods. The debris can quickly block storm sewers and drainage channels.
Below the ash, fires can cause the formation of hydrophobic soils, a layer that is impermeable to water, causing fast runoff. The threat lessens after the first year, though an inch of rain in a short time will still be enough to cause floods.
“It will be a repetitive event. Every time heavy rain hits that burn scar, there will be the potential for extreme flash flooding, with these mud and ash flows. It can be several consecutive years of constant flash flood concerns in that area,” Torgerson said.
Just ask people who live near the Hayman burn scar. Flash floods continue to plague the area, including a torrent in 2006, four years after the fire, that destroyed homes in Westcreek and washed out a large section of Colorado Highway 67.
So who is most at-risk? That’s a question that’s still being answered.
This week, experts from around the country arrived in Colorado Springs to form, along with local officials, a Burn Area Emergency Response (BAER) team, which has begun to analyze the burn scar and determine where the fire burned the hottest.
Team Leader Marc Stamer, a U.S. Forest Service official from California, said Tuesday it is too soon to say which areas will be most susceptible to floods. The group will spend about two weeks studying the burn scar, and within seven days of the fire being fully contained it will ask for federal funding to carry out work.
Through replanting and erosion-control measures like channels and barriers, officials will focus on the steepest and most-burned slopes, and areas that could pose a risk to life and property, Stamer said. Anyone who lives near a drainage channel or creek that flows from the fire zone is potentially at risk, he said.
That includes streams like Camp Creek and Fountain Creek along with northwest Colorado Springs neighborhoods. The weather service warns that Manitou Springs and Old Colorado City could be in the path of flooding.
In Manitou Springs, officials are considering installing concrete flood-control barriers along Fountain Creek, said city administrator Jack Benson.
“We can’t obviously predict what the rain event is going to be like but we do know we’re moving into the monsoon season,” Benson said.
The Colorado Department of Transportation is setting up rain monitors in the burn area and placing sandbags and equipment at the ready along U.S. Highway 24, which runs along Fountain Creek, said CDOT spokesman Bob Wilson.
“If it looks like it’s going to be a high rain event, they can mobilize a lot faster and get prepared, whether it needs to be for sandbagging or closing the road in advance,” he said.
Colorado Springs officials Tuesday began inspecting drainage and culverts in Mountain Shadows, the neighborhood hit hardest by the fire. Crews are clearing culverts blocked with debris and workers are on-call in case it rains, to respond to problem areas, said city spokeswoman Mary Scott. Residents near the burn scar who notice a drainage problem should call 385-5934 during normal working hours or the police non-emergency line, 444-7000, after hours, and crews will respond, she said.
A public meeting is planned for Thursday night at 7 p.m. to educate residents about flash floods and how they can protect themselves. The most important thing is to not drive through or enter any flooding water, said Torgerson, the meteorologist. Residents should follow the weather forecasts. A flash-flood watch is issued 12 hours before a flood is possible, while a warning means flooding is imminent.
If in doubt, head to higher ground, she said. Residents should also consider buying flood insurance, since floods aren’t covered by standard homeowners insurance policies.
But flood insurance takes 30 days to become effective. In the meantime, many in Colorado Springs will be looking at the afternoon rains as a double-edged sword.
Said Torgerson, “We need it in small doses. That’s how we need it.”
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