Citation | Silvestri, S and Gaboury, M. 2008. Habitat assessment and restoration opportunities in the Salmon River Watershed, Vancouver Island. Prepared for BC Hydro. |
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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 |
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