Abstract: Session A  9:45 am (Back to Session A)
Clear Creek Ecological Restoration:  Restoring Ecological Function in a Constrained Environment

Michael Rotar
Bozeman, MT

Authors:  Michael Rotar RESPEC, Bozeman, MT
Rebecca Pierce, Colorado Dept. of Transportation, Denver, CO
Richard McEldowney, Confluence Consulting, Bozeman, MT

The Colorado Department of Transportation (CDOT) has recently completed ecological restoration of a segment of Clear Creek near Georgetown, Colorado. Nearly 1,200 feet of channelized, incised and heavily armored channel flowing adjacent to Interstate 70 (I-70) was realigned and meandered through historic floodplain areas to increase bedform complexity and habitat diversity. Numerous constraints were overcome during the design and construction processes including presence of mine tailings within the floodplain, water rights issues, and various permitting requirements. The completed project affords CDOT the opportunity to mitigate potential impacts that may result from future highway projects along the highly-confined I-70 mountain corridor through creation of additional wetland areas.

The project area is contained within a steep-sided, relatively narrow, high-mountain valley. This geomorphic setting is a major component in defining the natural potential of the site. Additional factors, including manmade infrastructure and historic uses influenced the site’s restoration potential. Clear Creek currently shares the valley corridor with I-70, a frontage road, ponds and numerous home sites. Historic mining operations, which began in the 1850’s and continued with significant activity through the early 1900’s, resulted in deposition of metal-rich sediments in and along Clear Creek.

With mining came people and the need to transport them, as well as their goods and materials.  Construction of the transportation system, first the railroad and later roads and highways, resulted in stream relocation and straightening of the historical meander pattern. In fact, more than 50 percent of Clear Creek within the I-70 mountain corridor has been channelized as a result of highway development. Channelization reduced stream sinuosity and floodplain connectivity, both of which function to dissipate stream energy in natural and minimally disturbed systems. Attempts to mitigate the effects of channelization have occurred over time, including the addition of large boulders and drop structures in the channel. Channelization has also altered groundwater conditions near the creek by limiting or completely preventing seasonal flooding, which potentially affects recharge of the alluvial aquifer.

This successful project resulted in construction of 1,500 feet of new stream channel, greatly improved channel-floodplain connectivity, and increased instream and riparian habitat diversity.