Colorado Springs News, Sports & Business

Flood danger from Colorado wildfire burn scar to last for decades

By Garrison Wells Published: May 2, 2013

A child born today will be about 75 years old before the Waldo Canyon fire burn scar is healed to where it was before last summer's wildfire burned more than 18,000 acres and destroyed 347 homes.

What that new generation will face for decades is floods.

The increase in water flow 'is going to last for decades, ' said Dave Rosgen of Wildland Hydrology, which spearheaded a major watershed study that was presented to the public on Thursday.

And while the study is expected to lead to work that lessens the impact of smaller floods in the area, the big ones are going to hit and hit hard.

'The potential catastrophic floods, which will come, you're going to be living with them, ' Rosgen said. 'If you are living in a floodplain, pack your bags and be ready to go. '

The $425,000 Watershed Assessment of River Stability and Sediment Supply, study sparked by the Waldo Canyon fire, analyzed watersheds and floodplains and presented a mitigation plan for ways to speed recovery of the burned terrain.

A two-hour slide show was presented at the Pikes Peak Regional Development Center. The study was commissioned by the Coalition of the Upper South Platte.

'We know we have a very susceptible watershed, ' Rosgen said.

Indeed, even the usual storms this spring and summer in those areas 'can generate a 20-, 30-, 40-year flood, which is alarming, ' he said.

The study identified the four major watersheds impacted by the blaze as Camp Creek, Douglas Creek, Fountain Creek and West Monument Creek. It also identified areas that would produce the most sediment, including Douglas Creek, Wellington Gulch, Fountain Creek, Williams Canyon and Devils Kitchen - all hot spots.

Surface erosion, roads and trails, creeks and other sediment producers were among the flood risks that were studied.

Sediment control, Rosgen said, is critical to protecting areas against flooding. It's half the battle in fighting floods, he said.

When sediment piles up in stream channels, for example, it forces water to flow elsewhere.

'We've got to figure out how to route sediment to keep flood capacity down, ' Rosgen said.

On hillsides, erosion can be slowed by adding mulch, increasing surface roughness and re-vegetation, according to the study.

Roads can be rerouted, drained more frequently, even closed to unauthorized traffic.

Stream channels can be reconfigured to provide more stable flows.

While the cost to ease flooding is not clear, it's not going to be cheap.

Channel restorations can run from $25 to $44 per linear foot, sediment detention basins run from $1.70 to $10 per ton of sediment storage, aerial seeding and mulching runs $2,500 per acre and hand-crew surface erosion treatments are between $1,000 and $6,000 per acre depending on level of difficulty, access and the amount of work required. In an 18,000-acre burn area, it will add up.

Top sediment producing areas identified by the study will get attention first.

That's because a third of the area studied contributes 90 percent of the sediment.

The study, Rosgen said, 'tells us where we need to go. '

'It gives us a better understanding of what, where and so what, ' he said.

Some land restoration work began soon after the fire was extinguished and various groups and agencies have been involved with ongoing efforts, small and large. Rosgen said projects are underway, including Northfield Gulch sediment basins, north and south Douglas Creek sediment basins and on Flying W Ranch.

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