Summer rains were less intense in Douglas Creeks --
The information included the news that both escaped the worst of last summer's rainstorms. Even still, debris-laden water overwhelmed sediment basins and rushed abrasively down those drainages' six miles of concrete channels. As a result, the city expects to spend $5.1 million this year on what officials describe as emergency repairs.
According to a slide shown at the presentation, the funding will involve repairing concrete bottoms, building/maintaining sediment catchment basins, planting grasses and bushes upstream to offset Waldo Canyon burn area vegetation loss, cutting down trees that have grown inadvertently in the drainages and strategically placing creek- monitoring cameras,
Attendees also got a chance to look at a map estimating where significant flooding will occur along North and South Douglas if two inches of rain fall there in an hour. Although the number of affected homes and businesses was not available at the presentation, the map showed North Douglas potentially flooding both sides of Garden of the Gods Road along several hundred feet west of Chestnut Street.
Speakers included Bret Waters, director of the city's Office of Emergency Management; Tim Mitros, city stormwater engineering manager; Gordon Brenner, city fire recovery coordinator; Tom Magnuson of the National Weather Service; and Charles Jackson of the Federal Emergency Management Agency (FEMA). The meeting was at the Front Range Alliance
Magnuson gave a chronological summary of the four worst rainfalls last summer:
July 1 - Rain total of .6 inch in 10 minutes (a rate of 3.5 inches an hour). But the worst of it was in Williams Canyon while the intensity in Douglas Creek was much less.
July 10 - The Waldo Canyon area absorbed the heaviest downfall, with an inch of rain in about a half hour and Williams Canyon a little less. The Douglas creeks got a quarter to half that rate,
Aug. 9 - Waldo and Williams again took the brunt of a brief but hammering storm, this time with Williams getting a total of 1.6 inches, with rain pelting down at a rate of up to 5 inches an hour and even washing cars downstream in Ute Pass. Meanwhile, the total rain for North and South Douglas was between .5 and .8 inches.
Sept. 11-15 - The rains lasted longer but were less intense (rates mostly under .5 inch an hour). As a result, although there was damage, the flooding was not “catastrophic,” Magnuson explained.
Unfortunately, the earliest that flash-flood warnings can come in ahead of time is “at best 10 to 15 minutes,” Magnuson said. At the same time, authorities want to “minimize false warnings,” he pointed out. “We don't want to cry wolf” (and as a result have all warnings ignored).
The city has estimated the cost to fix all the problems in the Douglas Creek drainages at $20 million to $25 million. But with the $5.1 million available this year (as directed by Mayor Steve Bach), “we're doing what we can,” Mitros said.
In the past week, west of Centennial Boulevard, work crews could be seen fixing concrete channel bottoms along South Douglas Creek. The work is being engineered by a hired city consultant, the Matrix Design Group. Similar work, directed by Wilson & Co. (another city consultant), is occurring along the North Douglas drainage south of Garden of the Gods Road along about a half-mile east of I-25.
Both Douglas Creeks start in the hilly areas north and west of Garden of the Gods Road, crossing under it in concrete-lined ditches about a mile and a half apart as they drain east/southeast toward Monument Creek.
Westside Pioneer article