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Limited Colorado Springs storm damage shows success of flood mitigation

August 11, 2015 Updated: August 11, 2015 at 9:03 pm
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Fire debris from Mountain Shadows Fire, over three years ago, is strewn on Stoneridge Dr. in Mountain Shadows after a storm on Monday, August 10, 2015. (Jerilee Bennett/The Gazette)

When a group of children and adults bulwarked themselves into a room in the Alpine Autism Center on Monday, they were taking shelter from about 8 inches of floodwater that poured into the facility.

But if the Autism Center had not been protected by a nearby detention pond designed to catch flood debris, the center would have been hit with a wall of water. Despite the amount of debris and mud that coursed around the center, thanks to the flood mitigation, those who took shelter inside faced nothing more than a few inches of water.

Nonetheless, as the wave of water made its way into the Mountain Shadows neighborhood - carrying away a couple of cars - the scene might have looked like the failure of thousands of dollars' worth of flood mitigation work.

It was just the opposite, said Tim Mitros, the stormwater manager for the city of Colorado Springs.

Unlike two years ago, when an Aug. 9 storm flooded Manitou Springs and killed a man on U.S. 24, the blow of Monday's storm was significantly lessened by an extensive network of flood mitigation projects. The projects' continued success depends on keeping them clean and debris-free, which will likely require local governments to spend hundreds of thousands of dollars for years to come. Officials say that's a price worth paying to save lives and protect properties from flood damage.

The Autism Center's Monday flooding is but one example of how flood mitigation work came to the rescue. The center is protected by a retention pond with a pipe that channels water out of the area. A series of trap bags surround the center as backup in case the retention pond overflows. It's a system designed to slow, not stop, the impact of a flood.

"A big wave of water came down and went into the Autism Center," Mitros said. "If the trap bags hadn't been there, it would have taken the full force of that water. It would have been a lot more damage had the trap bags . that door would have been blasted right into."

Monday's storm propelled flood debris into basins around the region, and people in Colorado Springs and Manitou Springs saw the thick, sediment-filled water flow into drainages and culverts on its way down from the foothills.

Until Monday, the Pikes Peak region had been spared this year the kind of heavy rainstorm that tests the flood mitigation work throughout the Waldo Canyon burn scar, the denuded slopes of which pose a major flood threat every year.

Flooding is a particular threat in summer, when moisture-heavy and slow-moving storms form over the foothills west of Colorado Springs. For forecasters, the storms can be hard to pinpoint, and while the National Weather Service has models to predict where storms will form, the models can't show where they will hit hardest.

To manage the rainfall from these storms, local agencies have spent years building a network of flood mitigation systems - log erosion barriers, retention ponds and bigger culverts - to slow floodwaters that destroyed homes and killed residents.

But all of that money and all of the work can't win a war against Mother Nature. While residents may have been lulled by a quiet summer with no closures on U.S. 24, they shouldn't forget that flooding will remain possible for a long time.

"There is no way to stop the flood," said Carol Ekarius, executive director of the Coalition for the Upper South Platte, a nonprofit that has designed and built much of the flood mitigation work in the burn scar. "I never told anyone that the work we do would help stop floods. These are such scarred ecosystems after a fire like this, it will take decades for the ecosystem (to recover)."

The Pikes Peak region is a particularly tricky place to manage fire recovery. The 2012 Waldo Canyon fire burned through a steep forest grounded in Pikes Peak granite - a rocky, loose soil that behaves like ball bearings on a mountainside.

Before the fire, the soil couldn't hold much water; three years later, devoid of vegetation in areas and filled with water-resistant tree sap and oils, the soil holds even less. Mixing the post-fire soil with Colorado's late-summer monsoon is a recipe for regular flash flooding.

In past years, flooding has forced the shutdown of U.S. 24, filled downtown Manitou with mud and killed drivers.

To mitigate the flooding, detention ponds and log erosion barriers scattered throughout the scar trap sediment and slow the flow of water downhill. Small retention basins higher in the burn scar are designed to fill with sediment, whereas larger basins at the bottom of the foothills must be cleaned out periodically, Ekarius said.

Barring a severe drought, it will be years before Colorado Springs sees a summer without some kind of flooding, Ekarius said.

"When you are looking at these projects, we are mitigating impacts of the flood - and we are not stopping the flood," she said.

That reality makes the region's "new normal" of regular flooding no less dramatic. Video cameras around Colorado Springs captured flood images Monday - from a roll of sludge working its way down Camp Creek, to cars being swept from their parking spots in Mountain Shadows. While often horrifying to watch, each video showed signs of success to weather and flood mitigation experts, Ekarius said.

For instance, Camp Creek was still flowing; without a network of basins and debris nets above it, the creek's channel would have been easily overcome by big rocks and trees. The Autism Center will have some nasty cleanup, Mitros said, but that's better than grappling with damage from heavy boulders cascading downhill.

"To me, the trap bags really saved the Autism Center," Mitros said.

An unprecedented wet spring has meant that retention ponds around the region filled quickly. Last week, the city emptied the pond above the Autism Center, and crews now have to return to empty it again. While the costs of regular emptying can be steep, they are necessary to ensuring that expensive flood mitigation projects continue to work, Mitros said.

El Paso County and the city of Colorado Springs have spent millions of dollars to secure federal grants to help pay for flood mitigation, a cost Ekarius believes is justified by the alternative - frequent closures of the highway, lives lost and more homes and businesses destroyed.

Nonetheless, Ekarius has reflected on the enormous costs these projects incur, to build and to maintain, and wondered, is the money worth it?

"That is a question I struggle with myself at times," she said. "Where is the kind of proper balance for spending money on restoration? But my long-term look at this is it is still worth it."

CUSP has taken a few lessons from its work on the fire and had identified a few kind of flood mitigation structures that don't work as well.

But if she were to rewind the clock to July 2012, just days after the Waldo Canyon fire was extinguished, Ekarius would still push the importance of flood mitigation work.

"Do I believe that our work has saved more money than it has cost so far? Absolutely," she said.

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