Volume 12, Number 1 Spring 2001

Dry Creek Restoration Project

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by Brenda Mitchell, Queen of the River Consultants,
Cathy Leslie and Betty Solek, Rocky Mountain Consultants

 


 Photo 1
Photo 1:
Dry Creek — above road,
Channelized and overgrazed
 Photo 2
Photo 2:
Dry Creek – Original channel
next to channelized reach.
Note: natural meander pattern
and adjacent floodplain
Photo 3
Photo 3
Dry Creek above channelized portion.
Meanders intake but severe bank
erosion due to overgrazing
and vertical instability resulting
from downstream channelization
 Photo 4
Photo 4
Dry Creek – Just below 75th St.
Reference Reach. Channel meanders
intact, channel stable
 Photo 5
Photo 5
Dry Creek – above road
Prior to restoration
Photo 6
Photo 6
New fish/irrigation pond built fall,
2000 in place of channelized reach
 Photo 7
Photo 7
Dry Creek – channelized reach
below road. Prior to restoration
Photo 8
Photo 8
Dry Creek Floodplain Restoration
Initial grading work to install
meanders and floodplain
Photo 9
Photo 9
Dry Creek just below restoration site
 Photo 10
Photo 10
Dry Creek 1 mi below site
through business park
Photo 11
Photo 11:
Dry Creek – 2 miles below site
at Twin Peaks Mall

As you travel around the front range, you will see many of our streams and riparian corridors that have been greatly impacted by farming, grazing, roads, and urbanization. Many of these types of practices have left our streams channelized, rip-rapped, and downcut with a significant loss of valuable riparian habitat, wetlands, and functioning floodplain. Often streams that run through city limits are “restored” to much less than their potential due to constraints of adjacent development. These streams often look very park-like with a narrow floodplain, blue-grass lawns and landscaped trees planted at regular intervals. The St. Vrain Valley School District is building a new high school adjacent to Dry Creek, west of Longmont, Colorado. The District, assisted by Queen of the River Fisheries and Rocky Mountain Consultants, proposed an alternative design to the typical channelization often used in urban flood management designs in conjunction with a flood management project. A multi-disciplinary project team, including a riparian ecologist, a hydrologist, and engineers, saw the need to create additional flood capacity as an opportunity to re-establish the historic floodplain and associated riparian corridor. The need for a pond to provide raw water for irrigation then provided the opportunity to integrate a recreational fishery and wetlands for water quality management into the restoration project. The entire restoration project is intended to serve as a regional demonstration area for other greenway projects within the City of Longmont and other municipalities. In addition, the project will provide an outdoor classroom for elementary, middle, and high schools in the immediate vicinity. (See related story on page 8.)

Description of Ecosystem and Watershed
Dry Creek is a small (3rd order) perennial stream originating in the foothills 5 miles west of Longmont. Dry Creek flows into the St. Vrain River approximately 6 miles downstream of the site. The St. Vrain River is a moderate priority included on the State of Colorado 303d list.

Description of Environmental Challenges and Opportunities
St. Vrain Valley School District is building a high school, middle school, and elementary school in a newly developing area in southwestern Longmont. A city community park is also proposed for this area. At the site, Dry Creek has been extensively channelized and overgrazed causing significant bank erosion and loss of riparian values, floodplain function, and fish and wildlife habitat. FEMA flood studies showed that additional flood capacity was needed for development of the area and protection of downstream areas. In order to provide the needed flood retention capacity required by the City of Longmont, the City directed the construction of a regional stormwater detention facility at this location. As an alternative to the typical channelization often designed for urban flood management, the St. Vrain Valley School District saw the creation of additional flood capacity as an opportunity to re-establish the historic floodplain and associated riparian corridor. The need for a pond to provide raw water for irrigation then provided the opportunity to integrate a recreational fishery and wetlands for water quality management into the restoration project. The entire restoration project is intended to serve as a regional demonstration area for other greenway projects within the City of Longmont and other municipalities. In addition, the project will provide an outdoor classroom for elementary, middle, and high schools in the immediate vicinity. This project is one of the first to use this native restoration approach along a city Greenway and has obtained the approval of the City of Longmont. In fact, the City of Longmont is currently developing new Greenway landscape standards that encourage the use of native plantings and naturalized Greenway corridors.

Description of project and approach
The design for this area required balancing the following project elements:

  • Create an irrigation pond that will function as both a raw water supply and a recreational fisheries resource for high school and community park properties within the required 100 year detention pond.
  • Manage flooding and address the needs of stormwater retention.
  • Restore the historic function, pattern, profile, and dimension of Dry Creek stream channel and terraces.
  • Create wetlands along Dry Creek channel and adjacent to irrigation pond for water quality, and riparian habitat benefits.
  • Restore wetlands and native riparian communities, water quality, wildlife and fisheries habitat, and aesthetics by reestablishing a functioning floodplain and re-creating a stable channel.
  • Provide watchable wildlife and outdoor education opportunities for the local school children and community.

These opportunities and challenges are further depicted in the attached poster presentation.

Expected outcomes, benefits, results and schedule
The intent of re-vegetation is to create a densely vegetated native plant community that will serve as an important component of floodplain function. This habitat will include shrubby components to re-establish the native riparian and wetland community and stabilize the bank and terraces adjacent to the creek. Shrubs and trees planned for restoration include: Lance-leaf Cottonwood, Peachleaf Willow, American Plum, Common Chokecherry, Sandbar Willow, Red-osier Dogwood, Wood’s Rose, Golden Currant, Sumac, and Common Snowberry. No mowing or other impacts to the vegetation will be allowed. This native planting and riparian management will restore the ecosystem and enhance the diversity and abundance of birds (especially shorebirds and waterfowl), mammals, reptiles, amphibians, and fish.

Dry Creek is interconnected to Clover Basin Ditch. Within the past two years, Preble’s mice have been trapped along the Clover Basin Ditch. The restored riparian habitat along Dry Creek could provide an additional 6.5 acres of habitat for the mouse to occupy as it migrates along the Clover Basin Ditch. Other special status species that this project may benefit include: Bald Eagle, Ferruginous Hawk, Sandhill Crane, Long-billed Curlew, and Northern Leopard Frog. Public uses of the trail system through this restored area will serve to educate the community regarding the value and importance of natural stream corridors, riparian and wetlands, water quality protection, and wildlife conservation. This project will also serve as a model for urban flood management design projects proposed for other municipalities.

The Corps of Engineers granted a Nationwide 27 permit that addresses wetland and riparian restoration and creation activities because they recognized that the intention of this project is to restore historic wetland and riparian functions and values. Thus, the design of the Dry Creek restoration provided a substantial schedule benefit, by eliminating the time consuming Individual 404 Permit process, which would otherwise have been necessary.

Preliminary grading was completed in Fall of 2000 and construction will begin shortly on the remainder of the project. Final grading, installation of stream stabilization and fish habitat structures, and riparian and wetland planting will be accomplished by Summer 2000.

Stakeholder participation and project partners
St. Vrain Valley School District is the lead local agency for the project. The primary water right to be used for irrigation and establishment of the riparian vegetation is a very senior water right owned wholly by the St. Vrain Valley School District. Other project stakeholders include private developers (Brisben Development, M. Timm Development) who contributed land to be available for development of flood management objectives of the project. The City of Longmont is also a stakeholder as they will acquire both the community park in the vicinity of this project and Primary Greenway System along Dry Creek.

Dry Creek Tour
The Colorado Riparian Association and the WASH (Watershed Approach to Stream Health) group is co-sponsoring a tour of the project on June 14 from 1:30pm to 3:00pm at the new Longmont high school. The high school is located on Nelson Road between Airport Road and 75th Street. We will meet in the parking lot. Please RSVP to Brenda Mitchell at             303-651-2514       email brenda@qor.cncoffice.com or Betty Solek at             303-772-5282       email bsolek@long.rmcco.com by June 11.