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| Lefthand Creek Urban Stream Restoration Project |
Boulder County, Colorado |
Primary Project Type: Instream Restoration
Secondary Type: Riparian Restoration |
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Lefthand Creek upstream of farm bridge in June of 1999, view to west. As stream ... |
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Primary Problem: Channel Alteration
Secondary Problem: Change in Land Use |
| Main Restoration Action(s): Channel reconstruction, Floodplain reconnection, Riparian revegetation |
| Native Fish Focus: Common shiner, Stonecat |
Is this project part of a watershed scale restoration? No
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| Project Dates: October 2001 to April 2002 |
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Initial Monitoring:
Restoration Implementation: December 2001
Follow-up Monitoring: |
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Lead Agency:
Colorado Division of Wildlife
City of Longmont Departments of Public Works, Parks and Open Space
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| Project Location:
Lefthand Creek originates at the Continental Divide in the Rocky Mountains 27 miles west of Longmont, Colorado and flows continuously until it meets the Saint Vrain River in the southern part of Longmont. The project area is a 4,500-foot segment of Lefthand Creek in southeast Longmont just south of Ken Pratt Boulevard (State Highway 119).
For a map of the project area, click here.
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Project Description:
Historical agricultural practices, urbanization and channel straightening in Lefthand Creek resulted in a narrow entrenched channel with severely degraded aquatic habitat, a loss of riparian vegetation and a high percentage of fine sediment in the streambed. The Colorado Department of Transportation planned a two-mile extension of Ken Pratt Boulevard (State Highway 119) across the 100-year floodplain of Lefthand Creek. This would have required elevating about a mile of this major roadway four feet above the floodplain to protect it from floodwaters at a cost of about $650,000. In addition, it would have left the City’s future recreation center and other developable land in the floodplain. Therefore, several alternatives were considered: (1) construction of a dike to contain floodwater; (2) construction of a parallel overflow channel; (3) construction of a channel with riprap, and (4) creation of a natural channel system.
As stakeholders discussed the best option for stream restoration, fish habitat conservation requirements of the Colorado Department of Wildlife (CDOW) and wetland mitigation requirements by the U.S. Army Corps of Engineers eliminated the riprap and dike options. The CDOW required the upper 1,500 feet of Lefthand Creek not to be disturbed due to concerns over two state-threatened fish species in the nearby Saint Vrain River – the common shiner (Luxilus cornutus) and the stonecat (Noturus flavus) - as well as the existing self-sustaining brown trout population. Only the Saint Vrain/Lefthand Creek Watershed and the Plum Creek Watershed south of Denver are known habitats for the common shiner. The U.S. Army Corps of Engineers Nationwide Permit #27 required 1.2 acres of wetland creation for wetland impacts from the Ken Pratt Boulevard project and 1.25 acres of wetland creation for wetland impacts from the Lefthand Creek channel improvement project. |
| Project Goals: As more stakeholders became involved in the project, the City’s goals evolved from a riprap-lined channel to a natural stream channel with a narrower 100-year floodplain. The new design would conserve and create valuable habitat for native and exotic fish species, provide an extension of the City of Longmont’s extensive greenway trail system, and open 230 acres for construction of the new recreation center and other potential development. It would also eliminate the need and cost to elevate Ken Pratt Boulevard. |
Project Methods:
The project involved construction of a narrow 100-year floodplain along the 4,500-foot length of Lefthand Creek in the project area, and construction of 1,884 feet of new stream channel with a diversity of pool and riffle habitats suitable for both the existing fish populations such as brown trout and the state-threatened common shiner and stonecat fish. The new floodplain reduced the width of the existing floodplain from about 3,937 feet to 250 feet, opened up 230 acres for commercial and residential development, and allowed construction of a recreational trail as an extension of Longmont’s greenway system.
Approximately 2,616 feet of the existing stream channel remained unchanged. This stream segment contained coldwater habitat for brown trout such as overhead cover and shading, diversity of pool and riffle habitats, deep pools and gravel spawning areas in a low width/depth ratio channel. The new floodplain, constructed parallel to the existing unaltered reach of Lefthand Creek, served as an over flow channel during high stream flow events. An innovative runoff treatment system was installed to protect Lefthand Creek from polluted runoff from developed land near the creek.
Click here for more information on project methods.
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Photograph taken in November 2001 of the start of construction.
The new, narr... |
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Root wads and footer logs were used to stabilize meanders in the constructed cha... |
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Monitoring Data and Collection
Methods: Prior to the 1990s, when the project section was less disturbed, the fish community in the project area was almost exclusively comprised of native fishes. For example, in 1979, at a station near what would become the project reach, 13 species were observed, 12 of which were natives. Numerically, the ratio was overwhelming, as there were hundreds of natives and only four non-native largemouth bass. The natives included bigmouth shiners, plains killifish, plains topminnow and central stonerollers, all of which had disappeared by the mid-1990s. By 1994 the species ratio was seven native versus four non-native. In 2001, prior to restoration, there had been a very dramatic shift in species composition and a decline in diversity. There were only six species at the site, and the fish community was dominated by non-natives (45 of 72 fish sampled).
Prior to restoration efforts, the CDOW electroshocked the project reach and removed 14 species of fish. The fish were kept in a holding pond during restoration work and reintroduced into the restored reach, along with 500 offspring of wild common shiner broodstock.
After the project was completed, beavers resumed activity in part of the restored section of Lefthand Creek, creating pools and marshes that can’t be fully sampled by backpack electrofishing. But, in 2003 the CDOW sampled, with equal effort, a section of the restored habitat and a comparison section that was not restored. The unrestored section began about a half-mile upstream of the restored section. This is less separation than would be ideal, but the character of Lefthand Creek changes further upstream as it flows through the town of Longmont. This fact, combined with the elevation change above Longmont makes it difficult to find an ideal comparison reach. In the two comparable segments, 12 species of fish were found in the restored section, ten of which were natives. In the section that was not restored, ten species of fish were found, eight of which were natives. Overall fish numbers were about 17 percent higher in the restored section versus the section that was not restored (335 versus 279). The state-threatened common shiners were found in both reaches of the restored section but not in the upstream, unaltered stream segment. Other native species present were creek chub, fathead minnow, Johnny darter, longnose dace, sand shiner, green sunfish, central stoneroller, white sucker and longnose sucker. The CDOW plans to continue with the monitoring in the summer of 2005.
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Was this project effective
and how was this determined? The restoration of Lefthand Creek in Longmont, Colorado posed a unique challenge. Although the creek has been within city limits, it has been home to several native fish species including the state-threatened common shiner and stonecat, species unique to the Saint Vrain River system. The Saint Vrain River, which Lefthand Creek joins shortly downstream, has supported the best remaining transition zone fish community on the Front Range and probably in the state (verbal communication, Harry Crockett, CDOW fish biologist). In addition, there was a need to expand a major boulevard and a requirement to create wetlands as mitigation for stream restoration and boulevard expansion. As a result, a natural restoration design was chosen for the creek over the original plan to channelize and armor the project reach. This design eliminated the need to elevate the boulevard, saving the CDOW $650,000, and it opened up 320 acres of floodplain for development. The City of Longmont immediately built a recreation center and a museum on the property. The design also preserved and created habitat for fishes that included the state-threatened common shiner and stonecat. Post-restoration monitoring showed a full compliment of native fish (including the common shiner and stonecat) surviving in abundance, an indication the project successfully created the habitat conditions optimal for the fish.
Channel stability and revegetation efforts were also a success. A lower-than-normal spring runoff was ideal for establishment of the new vegetation on the stream banks of the new stream channel. In March of the following year, the new channel and floodplain was put to the test with exceptionally high runoff following a record snowstorm. The bank stabilization structures and plantings protected streambanks from erosion as water spilled onto the new floodplain and into the new overflow channel. In response, groundwater levels rose and germination of wetland species increased to over seven acres of diverse wetland, exceeding the 2.4-acre wetland requirement as mitigation for the roadway project. In 2006, the revegetation of the site continued to progress well. Many volunteer cottonwood (poulus deltoids supsp. Monilifera), peach-leaved willow (Salix amydaloides), and sandbar willow (Salix exigua) were at the site. Russian-olive (Eleaegnus angustifolia) has been a big threat to revegetation of the restoration wetlands. In both 2005 and 2006, manual removal of Russian-olive weeds was done by project managers and Wildlands Restoration Volunteers. Visit their website at http://www.wlrv.org/.
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Photograph taken in October 2006 of the restored Lefthand Creek, looking downstr... |
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Photograph taken in October 2006 of the restored Lefthand Creek, looking upstrea... |
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| Confounding Effects/Additional
Information: |
| Project
Specs (all specs are estimates): |
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Overall Estimated Cost:
$1.5 million
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| For more information on this project
contact: |
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David Hollingsworth, City of Longmont, Email: david.hollingsworth@ci.longmont.co.us
Laura Backus, Carter & Burgess, Email: laura.backus@c-b.com
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| This information
was collected by: Kristin Keith |
| Project last updated on: 3/19/2007 |
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