Spring 2016 Ecesis, Volume 26, Issue 1
The Little Truckee River runs between Stampede and Boca Reservoirs about 10 miles northeast of Truckee, California, and is one of the most popular and productive wild trout fisheries in the State of California. This resource is impaired however by regulated flow regimes, an associated lack of channel dynamics, and limited natural wood recruitment. Those who fish the Little Truckee River know this all too well, and there is a classic saying among anglers who fish the river: “90% of the fish occupy 10% of the water.” To address this issue, Trout Unlimited initiated an effort in 2011 to bring together restoration designers (Balance Hydrologics), the landowner (the U.S. Forest Service), experienced restoration contractors (Habitat Restoration Sciences), and local volunteers. A unique range of approaches were collaboratively developed and implemented to reduce the impact of restoration activities and optimize habitat benefits.
Stampede Dam is one of seven major dams in the larger Truckee River Basin that provides flood control and water for agriculture, municipalities, and maintenance of downstream habitat (Pyramid Lake). The construction of the dam in 1970 altered the natural flow regime and river processes and, in most cases, impaired downstream aquatic habitat.
Historically, large floods provided abundant spawning gravels, recruited large wood, and scoured deep pools, which all led to a dynamic channel environment and healthy complex aquatic habitat. Since 1970, the dam has effectively prevented sediment and wood from moving into the reach, and the flow regime has been modified such that peak flows are significantly lower than naturally occurring peak flows. With these processes impaired, the once highly dynamic river system has been reduced to a static channel with limited habitat complexity. While the regulated system now provides colder and higher base flows than was historically present, it lacks the habitat complexity once provided by the dynamic channel. Spawning gravels have been flushed downstream without replenishment, leaving behind an armored bed of coarse cobble, unsuitable for spawning. Peak spring runoff flows are significantly suppressed, reducing side channel and ephemeral wetland habitat that juvenile fish require for rearing. Adult fish compete for limited habitat and cover from predators, and recreational fishing puts further pressure on trout populations, with anglers concentrating on the limited segments of the river where trout exist.
Today, in the absence of these processes, the river no longer functions as an unregulated channel would. In a basin with complex water rights and flood control issues, dam removal is not a viable alternative at this time, so physical habitat enhancement is considered to be the next best approach to providing benefits for both fish and recreational anglers.
In 2011, efforts for a large-scale habitat enhancement project in this section of the Little Truckee River began, first with characterization of the system’s functional impairments, followed by development of a conceptual habitat enhancement design.
Trout Unlimited worked in partnership with biologists from the California Department of Fish and Wildlife and the Tahoe National Forest to complete biological monitoring and physical habitat identification in the proposed project reach of the Little Truckee River and documented poor habitat conditions while also characterizing the assemblage of native fishes and densities of benthic macroinvertebrates. Trout Unlimited also contracted Balance Hydrologics to complete a preliminary baseline assessment of the geomorphology and hydrology of the river and develop advanced conceptual habitat enhancement designs
Collaborative Analysis and Design Solutions
We desired a collaborative approach that encouraged volunteers and anglers to participate in all phases of the project. First, Balance Hydrologics worked with Truckee River Watershed Council volunteers on Truckee River Day to characterize existing habitat and measure existing pool depths and streambed sediment sizes. Second, Trout Unlimited volunteers and interns helped establish a correlation between streamflow depth and rate at multiple locations and a range of flow rates along the proposed project reach, offsetting need for an expensive and complex (and less accurate) hydraulic model. Third, a surveyor volunteered time and equipment to capture local topographic information. This information was then compiled and applied by professional geomorphologists to develop base maps and hydraulic relationships for design of large wood and root wad structures, including target locations and elevations to optimize localized scour, hydraulic complexity, and cover for fish.
Advanced conceptual designs were drafted by Balance Hydrologics and handed off to the Tahoe National Forest to complete the NEPA review process and to Trout Unlimited to obtain permits from state and federal agencies.
Adaptive and Cooperative Construction Approaches
In 2015, Habitat Restoration Sciences (HRS) joined the group to implement the design. Rather than coming onboard as a contractor that simply implemented a ‘100-percent Design Package’, HRS initiated a dynamic process whereby Forest Service biologists, Trout Unlimited staff, and Balance Hydrologics engineers and geomorphologists provided design revisions and guidance in the field during the construction phase, and HRS contractors developed innovative approaches to implementing the changes and meeting stringent turbidity standards, as required under the Lahontan Region Basin Plan. Collaboration and adaptability by the designers, landowner, and project proponent allowed for fluid and efficient implementation. Field constraints were identified and strategies were quickly developed to address unknowns as they arose.
Construction also required careful planning and collaboration to minimize impacts to existing habitat. Trout Unlimited worked closely with California Department of Water Resources, California Department of Fish and Wildlife, US Bureau of Reclamation, and Federal Water Master to reduce dam releases to a minimum flow of 15 cubic feet per second to facilitate construction. HRS had to develop low-impact approaches to dewatering and crossing the channel, while fisheries biologists with Tahoe National Forest provided services to protect or relocate fish from temporary crossings and diversions, and to monitor fish in upstream and downstream locations for stress during these reduced flows. Securing the large size of trees required for this project took ingenuity, and Trout Unlimited sought the help of local contractors who used community contacts to identify a nearby source of trees where clearing was taking place for construction of a new church. Finally, volunteers with Truckee River Day were again called upon to help with revegetation including seeding and planting of willow poles.
In all, 89 trees and over 150 boulders were strategically placed along a 1.3 mile stretch of the Little Truckee River to enhance adult trout habitat. Several existing secondary channels or backwaters were enlarged with additional wood and cover to enhance rearing habitat. Gravels were re-introduced in the immediate project area and directly downstream of Stampede Dam to enhance spawning habitat. Natural scour and bank erosion generated by introduction of wood and boulders may also help to sustain gravel recruitment.
Construction was completed in the late summer of 2015 and required 3 weeks of material staging, active in-channel work, erosion control, and revegetation. Since implementation, anglers have already reported fish occupying new habitat and improved recreational experience with fewer anglers concentrated in the once more popular segments of the river. Looking ahead, peak flows will continue to modify and improve existing habitat as introduced wood and boulders induce differing flow patterns and scour. Both biological and physical monitoring of the project is being carried out so that success can be evaluated, change can be detected, and strategies or adaptive management can be developed and implemented to respond to unforeseen circumstances as the system evolves.
Our process and outcome on this project demonstrate the power of teamwork and tangible results that can only be achieved through a collective vision and a wide range of expertise and experience. In the years ahead, we will continue to watch the river channel evolve, and take lessons in geomorphology, hydraulics, and fish behavior from our observations, just like we have done in years past. We will also take away the social experience, learn from the challenges of creating something together, and from the responses of users with an emotional connection to the river. Projects like these require a true collaboration between many individuals, agencies, groups, businesses, and volunteers — something much more than the simple technical training and background that we each bring to a project. — by Brian Hastings and David Shaw, Balance Hydrologics; Mark Girard and Loren Roach, Habitat Restoration Sciences; Dave Lass, Trout Unlimited; and Deborah Urich, U.S. Forest Service Tahoe National Forest