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Study shows regular floods can be lessened, but nothing will hold back the big ones 

A plan, but no salvation

Dave Rosgen looks like he rode in on a white horse.

He has the big belt buckle, the twinkling eyes, even the ivory cowboy hat. And then there's the fact that he's the nation's foremost expert on restoring watersheds after wildfires — arguably the one guy qualified to prevent our city from drowning in ash-choked water.

For months now, local leaders have breathlessly awaited Rosgen's Watershed Assessment of River Stability and Sediment Supply (WARSSS) study, a detailed explanation of how water will move off the Waldo Canyon burn scar and, more importantly, what we can do to stop it.

But as the study's finally presented, it becomes clear that Rosgen can't save us from the powers of nature.

His plan — thousands of pages long — represents a to-do list that likely will cost tens of millions. It's currently largely unfunded, and will take years to complete regardless. And then there's the biggest dose of reality: Even if the region does everything recommended, a five- or 10-year storm will still cause mass destruction and may claim many lives.

"The increase in flow is going to be with us," Rosgen tells the crowd. "It's not going to change a lot. Flood peaks are a reality for the future."

What the WARSSS can do is ease our suffering. The restoration work it recommends can hold back well over a million tons of mud in a normal monsoon season, ensuring that a two-year rain event doesn't take out a neighborhood. Plus, it will help the burn scar heal more quickly.

How quickly? Well, Rosgen notes that it could be 70 to 80 years before our flood situation goes back to "normal." But by helping nature along, we can shorten the age of monster floods and better control the smaller ones. That's if we act quickly, before floods decimate the hillsides and any semblance of a healthy stream system.

"We're going to have to get up into the watershed," Rosgen says, "and do something soon."

Yep, that's alarming

The Waldo burn scar is home to four major watersheds: Camp, Douglas, Fountain and Monument creeks. Those are fed by 89 smaller streams or "subwatersheds" that run for an aggregate 237 miles. Rosgen and a team of experts hiked nearly all those miles for the WARSSS.

That gave them the knowledge to determine which streams would produce the most damage the most often, which Rosgen turned into a Top 10 list meant to be used to prioritize mitigation work.

Surprisingly, the streams that feed Camp Creek above Glen Eyrie weren't included. Rosgen explains that the geography of the area makes it less likely to suffer from damaging annual storms, though it remains a potent danger in a major downpour.

Instead, North Douglas topped Rosgen's list. The creek has massive potential to deliver both water and sediment into the Mountain Shadows neighborhood regularly, and Rosgen notes that "pissant" pipes built to carry water through the urban landscape won't contain flood waters.

Williams Canyon, which hits central Manitou Springs from the north, occupies the No. 2 spot. The creek feeds a small underground pipe that cuts through a central neighborhood. It's not a great situation.

"We can't fix Williams," says Carol Ekarius, executive director for the Coalition for the Upper South Platte. "... The risk has always been there to some extent, but when it's a 100-year storm you think, 'Well, it's probably not going to be in my lifetime.' Well, the odds just changed."

Specifically, Rosgen says, "We're finding that just modest storms, like a two-year precipitation event, can generate a 20-, 30- and even 40-year flood."

Rosgen says he's hopeful that changes to creek beds can hold back some of the mud, dirt and rocks along Williams and Douglas. But the water that will come in a downpour will be too much for the pipes to bear, making flooding inevitable.

The other waterways on Rosgen's list feed Fountain and Monument creeks. (The entire study can be accessed at waldofire.org.) Fountain will affect communities from Cascade to Colorado Springs; Monument endangers two Colorado Springs Utilities water treatment plants and some homes.

More information on how flooding will affect neighborhoods will come as early as next week, in the first part of an "inundation study" (see here).

Back to nature

When Rosgen looks at a stream he sees two things: What it looks like now, and what it should look like.

Humans have long tried to harness water, guiding it through concrete channels, damming it, and rerouting it to accommodate homes and infrastructure. There's evidence of this in our cities — think of the concrete chute that runs down 31st Street through the Pleasant Valley neighborhood — as well as in our forests, where streams now follow unnatural paths or careen down roadways during storms.

Rosgen says the best way to fix problems caused by stormwater is to put things back as they were. That can mean adding curves to streams, making creek beds deeper, placing logs and rocks to break up the flow of water, or restoring natural flood plains and alluvial fans (areas where water spreads out and drops sediment).

In the Hayman Fire area, Rosgen and partners like CUSP have rebuilt some of these natural systems. The results are dramatic. Bank erosion on one stream was reduced by 655 tons per year per 1,000 feet of stream. Another area, built to capture sediment, can store 43,000 tons of mud and gravel.

Around Waldo, Rosgen wants to add sediment pools — small, deep basins built into a stream bed to slow water and collect dirt. He also has plans to improve or remove roads in the area, and to drop mulch and seed in order to prevent erosion on hillsides that eventually creates large gullies. Those gullies can rush water down a mountain, causing damaging flash floods in communities below.

Treating 33 percent of the channels in the 10 worst watersheds will eliminate 73 percent of bank erosion, sparing downstream neighbors more than 1.2 million tons of sediment in a year. Treating 4,211 acres of key hillsides will reduce hillside sediment production by 69 percent.

The good news is that the work — much of which must be done by hand — has been underway for months, and funding is growing. Local governments are looking forward to an infusion of $7.2 million in federal Emergency Watershed Protection money. Mayor Steve Bach recently pledged $8.8 million toward Camp and Douglas creeks. The county also plans to add $1 million to its stormwater effort. And Dana Butler, U.S. Forest Service hydrologist, says the service is working to secure more money for projects on its land.

The bad news is that there still isn't nearly enough funding, and much of the money that is in place comes with restrictions on how it can be spent.

Rosgen notes that treating a channel costs $25 to $44 a foot. Erosion treatment to an acre of land can cost $1,000 to $6,000. Based on those numbers, El Paso County Commissioner Sallie Clark and Greg Langer, a district conservationist for the Natural Resources Conservation Service, say the true costs of implementing the WARSSS is likely to be in the tens of millions. And that's just for work on the burn scar — it doesn't include huge amount of work that needs to be done to urban stormwater infrastructure.

"There were no costs really talked about here today," Clark told the Independent after a meeting on the study, "but if we look at what the Forest Service needs to do and what we need to do on private and public land, we're in the multimillion-dollar range. It could be $50 million or more as we look at going forward."

stanley@csindy.com

  • A plan, but no salvation

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