Tahoe Creek Restoration Project Wins Award

The Tahoe Regional Planning Agency has awarded Dudek and its subsidiary, Habitat Restoration Sciences (HRS), the Best in Basin award for the firm’s work restoring Lower Blackwood Creek.

Restoring native habitat was needed to correct over a century of disturbance that severely degraded the creek, a critical spawning area for rainbow trout living in Lake Tahoe and historically a habitat for Lahontan Cutthroat Trout and other native species.

Annual creek flows had caused heavy bank erosion and vegetation loss and a previous in-channel gravel mining operation increased sediment delivery to Lake Tahoe. The Blackwood Creek watershed contributed more than 21.5 tons of fine sediment per square kilometer per year: more fine sediment per unit of area than any other watershed in the Tahoe Basin.

The restoration project was designed to minimize fine sediment loading into the lake, and restore and improve stream habitat, water quality, and channel stability for the creek. Water clarity in Lake Tahoe has been a concern for a number of years and this project is the final piece of a comprehensive interagency restoration effort within the Blackwood Creek watershed. The restoration is a project of California Tahoe Conservancy, and contracted through the State of California Department of General Services. The construction work was conducted by Dudek’s construction subsidiary Habitat Restoration Sciences (HRS).

The project re-established a new channel segment, created small floodplain areas to accommodate peak flows, created riffles and pools for fish habitat, establishes riparian vegetation, and minimizes sediment deposition into the lake by slowing flow velocities in the lower 1,200 feet of the creek before it enters Lake Tahoe. Restoration efforts include several bank protection methods incorporating native plant revegetation and biotechnical techniques for enhancing fish and terrestrial habitat and stabilizing creek banks. Key elements of the project include:

  • Stabilizing eroding banks. Erosion potential was reduced by realigning segments of the channel for more sinuous flow and eliminating sharp bends, and incorporating in-stream woody material coupled with revegetation to redirect channel flows.
  • Restoring riparian cover. Fir and pine trees growing above an aspen stand were thinned to encourage ‘release’ of the aspens and to provide enhanced riparian cover. Release of the aspen stand seeks to return the floodplain to riparian cover, which was dominated by non-riparian conifer tree species. The thinned conifer logs were re-used within the creek for bank stabilization and aquatic and wildlife habitat.
  • Establishing vegetation. Native species consisting of cuttings, container plants, and herbaceous seed were planted along channel banks and within the floodplain. Vegetation establishment is intended to create Shaded Riverine Aquatic (SRA) habitat and stabilize banks, regulate water temperatures (through shading), and provide long-term nutrients to the creek/stream.
  • Creating fish habitat. Stream flow rates were modified to create ‘riffles’ with faster flow rates over rock bottoms in shallow areas and deeper pools of calmer water over fine sediments.

Though scheduled as a 2 year project, HRS completed the construction work in one season and within budget; HRS did not initiate any change orders for the work.

The project has been in place for 2 winters and HRS is conducting the final months of plant establishment maintenance. The creek realignment, bank protection structures and biotechnical treatments are intact and have stabilized the creek banks, fish are using the created habitat, and there is over 95% plant survivorship, well exceeding the performance requirements for the revegetation.