Cowichan River Stoltz Bluffs Stabilization Project

Dave began by saying he was going to tell us a story and would dispel the myth that engineers were boring.

It was a story where the stars and planets aligned to create one of the most interesting jobs of his career, because the money and resources all came together at the right time. Everyone involved was critical in the successful completion of the project.

In the summer of 2006, KWL designed and constructed river works (new channel, terrace and berm) on Vancouver Island's Cowichan River, adjacent to Stoltz Bluffs. This is the largest stream restoration project on Vancouver Island in over 20 years. Initially, KWL analyzed patterns of fine sediment sources and concentrations along the river between Cowichan Lake and Duncan, which suggested that Stoltz Bluff is a major source of fine sediment to the river. This sediment covers spawning gravels downstream and is devastating to fish egg survival.

The channel stabilization works are intended to stop the river from undercutting the bluff, and also to catch fine material delivered to the base of the slope from upslope failures. The terrace and berm was protected with a combination of low bendway weirs, a riprap stone toe and bioengineering techniques such as soil wraps and brush layers. The river flow was diverted around the construction via an existing floodplain back channel.

Future phases of the work will address slope stability issues through geotechnical investigations, determine the mechanism of failure, and implement further mitigation works.

The Cowichan River, a designated heritage river, is managed by a roundtable of stakeholders including the Cowichan Tribes, BC Ministry of Environment, Fisheries and Oceans Canada, and others. Public interest in the project has been high, and the construction was captured in a documentary by Shaw Cable funded by the Cowichan Valley Regional District.

The project was funded primarily from the Pacific Salmon Commission and the Georgia Basin Living Rivers program with other funding partners such as BC Highways, Catalyst Paper and Timber West. The project was constructed by Johel Bros Contracting with assistance from KMC the Cowichan Tribes contracting company.

For more information click here http://www.forrex.org/sites/default/files/publications/articles/streamline_vol11_no2_art6.pdf

You can hear Dave's presentation here: http://www.dcphotoart.ca/rotary/Dave_Murray_July23-14.mp3