The
Chilliwack/Vedder River is one of the most important recreational
rivers in British Columbia. It is a world-class river that supports
all of the Pacific species of salmon and steelhead and offers one
of the largest steelhead and salmon runs in the province. It is
one of the most heavily sport-fished rivers in the province with
sport anglers coming from around the world. The Chilliwack River
provides opportunities for world-class river rafting and kayaking.
The Chilliwack River Watershed also provides opportunity for hiking
and camping as well as containing a vibrant residential area. Survey
studies conducted by DFO in the fall of 2001 indicated that 1450
sports anglers fished the river on an average fall day.A study by
the City of Chilliwack indicated that 2,600,000 people visitedthe
Chilliwack River Valley for recreational purposes in 2001.
Environmental
Concerns
The
floods in the Chilliwack River Valley in November1989 and 1990 left
a number of clay slide areas severly eroded and open to continued
erosion which caused large slumps in November 1995 at the Tolmie
Clay Slide and in January 1997 at the Slesse Park Clay Slide, each
temporily blocking the river and leaving it silted for months. Over
the last 80 years the valley has lost the giant cedar trees that
naturally stabilized eroding areas. In historic times, when erosion
started, large trees would fall into the river and because of their
size and roots these trees would become anchored, and swing to protect
the bank from further erosion. An example of this natural stabilizing
process in action is in the ecological reserve at the headwaters
of Chilliwack Lake. At several clay slides in the lower Chilliwack
River Valley erosion now takes place during the rainy seasons with
little abatement which leads to accelerating erosion and resulting
mud flows and large slumps . The Tolmie Clay Slide is the largest
and most urgently needing stabilizing.
Problems caused
by this erosion are as follows:
Siltation
and the degradation of 28 km of downstream fish and wildlife habitat
in the Chilliwack/Vedder River
Loss of fish
spawning and rearing areas and wildlife habitat
A loss of
sports fishing opportunity due to "coloured" water
A hazard
to sports fishermen and other recreational river users from sudden
clay slide slumps
A threat
to the safety of residential areas from a clay flows, floods and
erosion of property
A loss of
economic activity due to decreased recreational use and loss of
tourist trade.
The engineers
predict that unless these slides are stabilized the undercutting
at the slides will continue, erosion will accelerate and the problems
will get worse.
The Solution
New,
innovative, environmentally friendly and cost effective engineering
techniques that replicate the action of the giant cedars of the
past can be used to stabilize these slides and solve the above problems.
These techniques include protecting the slide toe with groynes and
"large woody debris" securely anchored with rock, and
reducing surface erosion with bioengineering methods such as terracing
and vegetating. Stabilization using these techniques can help restore
some of the biodiversity of historic times and produce a more healthy
and sustainable watershed that will improve the environmental, social
and economic well being of the Fraser Valley.
The
Chilliwack/Vedder River is one of the most important recreational
rivers in British Columbia. It is a world-class river that supports
all of the Pacific species of salmon and steelhead and offers one
of the largest steelhead and salmon runs in the province. It is
one of the most heavily sport-fished rivers in the province with
sport anglers coming from around the world. The Chilliwack River
provides opportunities for world-class river rafting and kayaking.
The Chilliwack River Watershed also provides opportunity for hiking
and camping as well as containing a vibrant residential area. Survey
studies conducted by DFO in the fall of 2001 indicated that 1450
sports anglers fished the river on an average fall day.A study by
the City of Chilliwack indicated that 2,600,000 people visitedthe
Chilliwack River Valley for recreational purposes in 2001.
The
floods in the Chilliwack River Valley in November1989 and 1990 left
a number of clay slide areas severly eroded and open to continued
erosion which caused large slumps in November 1995 at the Tolmie
Clay Slide and in January 1997 at the Slesse Park Clay Slide, each
temporily blocking the river and leaving it silted for months. Over
the last 80 years the valley has lost the giant cedar trees that
naturally stabilized eroding areas. In historic times, when erosion
started, large trees would fall into the river and because of their
size and roots these trees would become anchored, and swing to protect
the bank from further erosion. An example of this natural stabilizing
process in action is in the ecological reserve at the headwaters
of Chilliwack Lake. At several clay slides in the lower Chilliwack
River Valley erosion now takes place during the rainy seasons with
little abatement which leads to accelerating erosion and resulting
mud flows and large slumps . The Tolmie Clay Slide is the largest
and most urgently needing stabilizing.
New,
innovative, environmentally friendly and cost effective engineering
techniques that replicate the action of the giant cedars of the
past can be used to stabilize these slides and solve the above problems.
These techniques include protecting the slide toe with groynes and
"large woody debris" securely anchored with rock, and
reducing surface erosion with bioengineering methods such as terracing
and vegetating. Stabilization using these techniques can help restore
some of the biodiversity of historic times and produce a more healthy
and sustainable watershed that will improve the environmental, social
and economic well being of the Fraser Valley.