Cottonwood Creek Reclamation
Cherry Creek State Park, Colorado
Two miles of severely eroded stream channel in the Cherry Creek State Park near Denver, Colorado, were reclaimed to a stable and ecologically diverse prairie stream in this transformative project. Designed as a pollution reduction project, the incised channel, a casualty of urbanization and greatly increased stormwater flows, was regraded to create a shallow low-flow channel that contains base flows but allows flood flows to overtop the banks and spread into the adjacent riparian floodplain. This wide and shallow flood flow reduces flow velocities and depths (and thereby erosion), and provides natural irrigation for the development of diverse riparian corridor vegetation in the floodplain. The project ultimately reduces the transport of nutrient-laden sediment into the Cherry Creek Reservoir, which is downstream of the project and is part of an on-going strategy by the Cherry Creek Basin Water Quality Authority (CCBWQA) to maintain a healthy reservoir resource. Reduction of phosphorus pollution is the key objective of the Basin Authority’s projects, and the Cottonwood Creek project achieves an estimated reduction of 800 pounds of phosphorus per year–a reduction of about 25% of the total phosphorus contribution from Cottonwood Creek to the Cherry Creek Reservoir.
The channel was stabilized using three levels of bio-engineering techniques, ranging from light-duty geotextile and seeding, to a more heavy duty technique employing rock-reinforced willow bundles combined with geotextile. The overall approach technique proved highly cost effective and saved hundreds of thousands of dollars over traditional streambank stabilization.
A Stream principal led design while with Wenk Associates.