Water Stewardship Information Sources

Citation Northwest Hydraulic Consultants Ltd. 2008. Salmon River Big Tree Main Side Channel Planning and Design. Prepared for BC Hydro.
Organization BC Hydro
URL https://www.bchydro.com/bcrp/projects/docs/07.CBR.01.pdf
Abstract/Description or Keywords Salmon and steelhead escapements to the Salmon River have declined to roughly 25% of
historic numbers (BC Hydro 2000; Lill 2002). Because Pacific salmon are considered
keystone species that return energy (essential fatty acids) and marine-derived nutrients to
many nutrient-poor, granitic watersheds on Vancouver Island, ecosystem productivity has
declined along with spawning escapements. Reduced nutrient recycling is further
exacerbated by poor carcass retention because simplified stream channels lack large
woody debris and pool depth and have a reduced ability to retain carcasses (Slaney et al.
The quality and quantity of suitable and stable fish habitat in the Salmon River has
declined significantly over the last half century. Reduced upslope water retention and
hydro diversions have led to lower summer flows in stream channels, reduced habitat
suitability (for aquatic insects and juvenile salmonids) and increased competition for
“quality” space. The BC Hydro diversion facility, built in 1958, severely restricted
upstream fish passage until construction of a fishway in 1992 (BC Hydro 2000). A screen
on the diversion installed in 1986 reduces downstream entrainment of juvenile and adult
fish, though losses remain an issue when the screen trips or when it is not required during
diversion. Logging of trees from the riparian zone has increased bank erosion and
sediment loading, and has caused significant widening of channels. Spawning beds have
shifted and/or scoured, and channel complexity has declined, with fewer pools and stable
large woody debris (LWD) jams to provide optimum rearing conditions for juvenile fish
(Murphy 1995).
Off channel habitat creation is a cost effective method to improve fish production in
Vancouver Island river systems. There is an existing natural side channel complex on the
left bank of the Salmon River in the vicinity of Big Tree Main down to the confluence of
the Memekay and Salmon Rivers. Most of the channels and water pools dry completely
in the summer, or become so small that predators have easy access to the stranded fish.
In the summer and fall of 2006 the Sayward Fish and Game Club, DFO, and BCCF crews
identified a potential side-channel project site on the Salmon River. Preliminary
feasibility work was completed by BCCF crews and Northwest Hydraulic Consultants
Ltd. (nhc). The feasibility work involved looking at channel grades, identifying two
possible intake locations, walking the proposed channel alignment, and walking the
remnant flood channels in the lower reaches.
This BCRP project funded the planning, engineering, and permitting work in preparation
for channel construction during the summer of 2008. This report presents the
topographical surveys, test well data, cultural resources investigations, side channel
designs, permitting, cost estimates, and construction planning.
Information Type report
Regional Watershed Vancouver Island North
Sub-watershed if known Salmon River
Aquifer #
Project status complete
Contact Name
Contact Email