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Another slump occurred at the Tolmie Clay Slide on March 10th during the heavy rains. This slump was small and only on one part of the slide area but still it caused considerable river siltation for several days. More slumps and possibly much larger ones are eminent unless stabilizing action is taken. Siltation from these slides and slumps smothers downstream river habitat with a coating of clay, sealing spawning gravel and killing aquatic life. Steelhead, Chinook, pink and chum all spawn in the 28 kilometers of lower river mainstream and smolts from upstream on their migration route to the ocean must pass through this area. When plankton and other aquatic life are smothered there is less food for fish fry and smolts, resulting in more competition and more losses due to stress. Many studies have indicated that the single most important factor in maintaining the sustainability of a fishing resource is preserving the quality of its habitat. The Chilliwack River Action Committee has some funding in place to do the stabilization work on the Tolmie Clay Slide and hope to get started this summer. So far funds have come from our Help Habitat Chinook Salmon Derby, Fraser Valley Regional District, Chilliwack Fish & Game Protective Association, Chilliwack River Valley Ratepayers Association, Gaming B.C. (Bingo), Trans Mountain Pipelines and the Pacific Salmon Foundation. Some minor erosion and siltation is natural in a river system and does not significantly degrade habitat as is the case in the ecological reserve in the headwaters of Chilliwack Lake. This would have been the case in the Chilliwack River Valley prior to historic logging and development as the valley floor was covered with giant cedars, the evidence is that many of their stumps still remain. These giant cedars would have had a stabilizing effect on the river. The ecological reserve is an example of this as it contains some of the largest conifer trees in the province and many log jams along the banks of the river. When a cut bank starts to erode a giant cedar falls into the river and swings around, other woody debris will collect and the bank becomes protected from undercutting; erosion may continue, but at a much slower rate. This large woody debris at the sides of the river produces swirls, pools, hiding places, and a food source for fish from insect life that lives in the rotting wood. The lower Chilliwack River has over the years become depleted of the giant cedars and this type of large woody debris and therefore vulnerable to excessive erosion, unstable clay slides and slumps. The Chilliwack River Action Committee is taking action to stabilize the Tolmie Clay Slide using bioengineering techniques that help replicate these natural stabilization process of the natural forest of the past. Plans are to construct groynes built with large woody debris anchored with large rock. This type of stabilization adds biodiversity and is cost effective, even less expensive than the old erosion control methods of building long straight riprap dykes. We know that fishing licences and fishing regulations are needed to protect the resource for the future. However, as scientific studies indicate, the single most important factor in maintaining the sustainability our fishery resource is preserving the quality of its habitat. If we can restore some of this habitat to a degree of the quality of the past is it not our moral responsibility to do so? It is in everyone’s interest that the Tolmie Clay Slide be stabilized and it should be done using the most cost efficient and best bioengineering techniques available. The Chilliwack River Action Committee works for implementing habitat restoration using these techniques to achieve the long-term health and sustainability of the Chilliwack River watershed. David Lamson, President |
