Silverhope Creek Mainstem Restoration


Year 2008
Organization The British Columbia Conservation Foundation
Project type Habitat
FSWP funding source DFO Fraser Basin Initiative
Grant amount $22,000
Total project value $88,080
Other project funders

HCTF
Ministry of Transportation
Ministry of Environment
BC Conservation Corps

ID number

08 HPR D106

Location: Fraser Valley, Hope, BC

Project Summary

Purpose:
Historical highway and logging activities on the Silverhope watershed have resulted in significant aquatic habitat degradation over past decades.  Past streambank logging has removed exceptionally large red cedars and other old-growth conifers which overtime has resulted in considerable channel instability, widening, and sedimentation.  The Silver Skagit Forest Service Road runs parallel to the Silverhope from Hope to Ross Lake State Park (United States).  In order to prevent washouts and erosion on streambanks that have been weakened by poor riparian logging practices, extensive rip rap armoring/dyking exists. The destabilized river banks have generated aggressive lateral river migration releasing extensive substrate to the stream channel.  Gravel and cobble originating from the protective banks has in-filled functional mainstem boulder habitat and juvenile rearing pools (Babakaiff, 1998).  Overall, this degradation has resulted in substantial losses of steelhead and char habitats, particularly vital over-wintering refuges.

As a result of a confined floodplain and reduced stream bank friction due to armoring, greater overall velocities are experienced during high precipitation and snowmelt events.  The altered hydraulic condition combined with removal of large riparian conifers has contributed to overall channel instability.  The inability for the river to function naturally has prevented river meanders and woody debris jams that assist in the development of pools, riffles and runs, highly favorable to juvenile salmonids.  According to the results from the 2003 Silverhope Creek fish habitat assessment, large wood and associated log jams are the primary deficiency (Slaney 2003).  The proposed mainstem placement of anchored woody debris structures, boulder clusters and bar stabilizers will benefit the ecosystem by generating localized stream depth in the form of scoured pools, increased localized velocities, enhanced gravel storage, and the collection of organic matter.  As an added benefit, abundant invertebrate communities will form on the wood and rock, improving energy resources for juvenile salmonids in a stream of relative high natural productivity.  Although most benefits will accrue to juvenile fish, adult spawning habitat will be improved by creating high quality stabile gravel deposition areas behind structures thus improving egg-to-fry survival.
The goals of this project are to accelerate the natural recovery of riparian vegetation by creating habitat structures that play a key role in bank stabilization, to re-establish high quality juvenile salmonid rearing habitat with the addition of large woody debris, and increase stream productivity, smolt yield and ultimately adult returns.

Method:
This project will rehabilitate up to one km of the mainstem Silverhope Creek by constructing 10 large wood fish habitat structures following guidelines set out in a 2003 fish habitat prescriptions report (Slaney 2003). In this document, suitable sites for wood structures have been identified and specifics relating to structure design have been proposed.  Owing to the unstable nature of the banks in the region and the lack of mature riparian habitat, the large wood structures will be constructed so as to provide considerable bank protection therefore reducing local bank erosion, and will be heavily ballasted and secured. 
The prescribed instream sites in Silverhope Creek provide 10 triangulated LWD structures.  The LWD structures would add from 60 to 75 pieces of large wood to the channel, plus collect additional driftwood during subsequent high flow events.  The addition of the trapped woody debris would increase the biological rating to fair/good quality habitat based on the Fish Habitat Assessment Procedure for forested streams.  Introduced and trapped woody debris also increases aquatic insect abundance and will aid in trapping fine organic debris increasing the system’s ability to store nutrients.  All structures will be engineered and designed to perform certain functions at each prescribed location.

BCCF fisheries technicians who will be responsible for implementing this project have completed three years of successful habitat rehabilitation at the Silverhope mainstem, building relationships with local contractors in the process.  This project will involve the use of a conventional excavator to load ballast rock from km 17 on the Silver Skagit road, a rock truck to move the rock to the restoration reach near km 14 (figure 3), a front-end loader to move the rock to the site locations.  A rubber-wheeled Spyder excavator will complete all instream construction resulting in minimal impact on the aquatic environment.  Access to the proposed restoration reach will not be difficult.  A short 5 m spur road will be constructed off an existing low dyke that is vegetated only with young alder and grasses.  This spur road provides access to a vast expense of gravel bar from which two thirds of the restoration site can be accessed.  The remaining sites are accessible directly off the main forest service road.

Due to the unstable nature of the mainstem, the wood structures will be ballasted with rock to a 1.25 to 2-times safety factor and then cabled with galvanized steel cables to ensure secure placement at the installed location (D’Aoust, Millar, 1999).  As an added safety precaution the main structural components of each wood structure will be anchored to hard points that may include buried deadman boulders and where available mature conifers in the riparian zone.

Outcomes:
Deliverables will include:
a) High quality and increased quantity of juvenile steelhead rearing habitat with the addition of large woody debris, and bar/bank stabilization.
b) Project completion report
c) Involvement of local First Nations and stream stewardship groups.

To complete this project we will construct up to 10 triangulated large wood fish habitat/bank stabilization structures in the Silverhope mainstem.  This project will provide bank stability and restored habitat to approximately one km of a heavily impacted reach of Silverhope Creek upstream of 2.5 km of previously restored stream channel.  A completion report will be completed following implementation.  Routine monitoring of the project will be done by BCCF personal, especially after seasonal high water events and periods of low water to ensure the project is functioning both structurally and biologically.  Routine monitoring will follow the Effectiveness Monitoring Guide for Stream Restoration conducted for the Greater Georgia Basin Steelhead Recovery by Slaney (2007) developed and used by the Steelhead Recovery/Living Rivers Program.



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