Importance of the Chilliwack/Vedder River

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.