Canadian Consulting Engineer

Study of Watersheds in B.C.; Award of Merit; Management Option A — Extensive Treatment Scenario

October 1, 2000
By Canadian Consulting Engineer

Acres International in association with B. A. Blackwell and Associates, Northwest Hydraulic Consultants, J. M. Ryder and Associates Terrain Analysis, Oikos Ecological Services,Phero Tech, Timberline F...

Acres International in association with B. A. Blackwell and Associates, Northwest Hydraulic Consultants, J. M. Ryder and Associates Terrain Analysis, Oikos Ecological Services,

Phero Tech, Timberline Forest Inventory Consultants, B. Thompson

Category: Studies and Software

In the late 1980s public debate over how to manage the 54,000-hectares of the Greater Vancouver Regional District (GVRD) three great watersheds reached its peak. At issue was whether to continue to allow practices such as road building and timber harvesting to continue in these watersheds, namely Capilano, Seymour and Coquitlam.

By 1991, the Greater Vancouver Regional District concluded that a detailed ecological inventory of these watershed areas was required. The project is the most comprehensive landscape level inventory of its kind in Canada.

The primary focus was to determine what effect the introduction of sediment caused by disturbances to the vegetation and terrain had on the quality of drinking water in reservoirs, and how the effects could be mitigated. Increased sedimentation can cause turbidity and reduce the effectiveness of disinfectants like chlorine.

The $4.3 million, seven-year ecological inventory and modelling project was carried out by a multi-disciplinary team of engineers, geoscientists, ecologists and biologists led by Acres International in Vancouver.

The team developed a comprehensive database of the watershed terrain, its stability, vegetation, forest cover, system of streams, road network and other features. Through a process of air photo interpretation and on-the-ground surveying of several landscape units, the team carried out bioterrain mapping to provide Geographical Information System (GIS) maps that link vegetation zones with terrain features. The team evaluated disturbances such as forest fires, the outbreak of insects and disease, and slope failures to identify the relationship between these and the amount of sediment carried to the reservoirs. They considered management interventions such as silviculture treatments, road upgrading and other erosion control measures.

From these studies the team developed hazard and risk maps. Sources of fine sediment (with particles less than 63 microns) were identified. The team then estimated how much fine sediment disturbances would yield per year. These changes in annual sediment yield were then modelled over a 200 year period under various scenarios.

Together, the extensive database and models provide a sophisticated decision support system with which the Greater Vancouver Regional District will be able to evaluate strategies for maintaining water quality. The study also provides a means for achieving improved biodiversity.CCE

Project name: Ecological Inventory and Modeling Project for the Greater Vancouver Regional District

Award winners: (as above). Prime consultant: Acres International

Project team leaders: R. Scott Hanna, Tony B. Wong, Bruce Blackwell, June Ryder, P. Geo., Ken Rood, P. Geo., Don McLennan, Jerry Carlson, Mike Mastine, Bill Thompson, Robin Taylor

Study of Watersheds in B.C.


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