Water Stewardship Information Sources

Citation Silvestri, S and Gaboury, M. 2008. Habitat assessment and restoration opportunities in the Salmon River Watershed, Vancouver Island. Prepared for BC Hydro.
Organization BC Hydro
URL https://www.bchydro.com/bcrp/projects/docs/06.CBR.06.pdf
Abstract/Description or Keywords In the summer of 2006 and 2007, level 1 and 2 fish habitat assessments were completed in the
Salmon River watershed by BCCF, LGL Limited, Comox First Nation and Northwest Hydraulic
Consultants staff. The objectives of this project were to collect the appropriate fish habitat data
to determine current factors limiting fish production and to identify and develop high priority and
cost-effective restoration options to mitigate the limiting factors, while also trying to address any
impacts as a result of BC Hydro diversion dam operations. The area selected for investigation in
the mainstem Salmon River was from the South Fork ML Bridge to the Memekay ML Bridge,
excluding the canyon section upstream of the BC Hydro diversion facility. A second area of
investigation was in Grilse Creek, a tributary in the upper Salmon River, from the anadromous
barrier to the Salmon River confluence.
In total, 13.19 km of stream habitat was assessed in the Salmon River mainstem below the South
Fork ML Bridge, while 4.15 km of habitat was assessed in Grilse Creek. Additionally, several
thousand meters of off-channel habitat were also assessed in both the mainstem and Grilse
Creek. Channel morphology and habitat characteristics were found to be of mixed condition
through all reaches. The mainstem Salmon River above and below the confluence of Grilse
Creek has moderate gradients and is dominated by cobble-boulder substrates. Disturbance
indicators such as continued bank erosion, multiple channels, mid-channel cobble-boulder bars
and large woody debris (LWD) lying parallel to the bank are prevalent throughout. Similarly,
channel morphology and habitat characteristics of the Salmon River below the BC Hydro
Diversion Dam appeared to be of comparable health and condition, however less bank erosion
and more bedrock controls were noted. LWD within the river channel was also less prevalent.
In Grilse Creek, level one habitat assessment results noted improvements in channel morphology
in the upper anadromous section as mean channel and bankfull widths were less; however pool
frequency and overall cover were poor when compared to results gathered by LGL Limited in
2002.
Our detailed habitat and restoration assessments indicate a requirement for improved habitat
conditions through most reaches, however few viable restoration opportunities exist within
Reaches 4, 5 and 5A, and within reaches USR1-4 as channel characteristics and gradient restrict
cost-effective opportunities that are not deemed high risk.
In Grilse Creek, opportunities to improve pool frequency, the number of holding pools, and
instream and overhead cover for summer and winter stream rearing species exist through the
placement of LWD at key sites. This work follows prescriptions designed by LGL Ltd. in 2002
and constructed in 2003 by Mainstream Biological Consulting. Inspection of the completed
works in the summer of 2007 noted a large degree of failure, resulting in accelerated bank
erosion and reduced functionality of the sites. Prescriptions for constructing 14 new LWD
structures and repairing 11 previously built structures have been provided in this report.
As part of this project, initial investigation and feasibility of a side-channel complex near the Big
Tree Mainline Bridge was also assessed. As a result of this initial work, a feasibility and design
proposal was submitted to BCRP for the 2007 season. Further information on this project will be
made available once this work is completed (work being completed by Northwest Hydraulic
Consultants).
Information Type report
Regional Watershed Vancouver Island North
Sub-watershed if known Salmon River
Aquifer #
Comments
Project status complete
Contact Name
Contact Email