Accommodating Floods Instead of Destroying Waterways

The flood management story of Boulder, Colorado, includes a successful encounter with a 1,000-year rain event, and its lessons are less about concrete and dams than one might think.
Alissa Walker / flickr

Will Doig writes a detailed long read about the disparate experiences of last fall’s flooding in Colorado, when tried and true flood plan maps proved inadequate to the scale of a 1,000-year rain event, but a more subtle approach to flood control proved successful.

Boulder escaped some of the brunt of the storm but also a lot of potential damage by “focusing not on large engineering solutions, but more on good land-use planning and stewardship.”

“The philosophy was clear: A light touch tends to be more effective than a heavy hand. For instance, in the bed of Boulder Creek, drop structures were created out of rocks where the elevation of the creek falls sharply — small waterfalls that concentrate the flow of the water inward to keep it from overflowing its banks. Similarly, placed at strategic points near the sides of the creek were jagged rocks called “rip rap” that disrupt the momentum of the flood. These mechanisms are still found in the creek today, many of them placed near bridges to try to tame the water where it might do the most structural damage.”

A lot of that philosophy comes from Boulder’s relationship with its waterway, according to David Driskell, Boulder’s executive director for community planning and sustainability: “We don’t do large trapezoidal concrete channels to try to protect life in a flood. We understand our creek is an amenity that people value the 99.9 percent of the time that it’s not flooding.”

Full Story: You Can’t Stop Urban Flooding

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