Water Stewardship Information Sources

Citation Thonon, I. 2006. The Fraser River debris trap: A cost benefit analysis. Prepared for the Fraser River Debris Operating Committee.
Organization Fraser River Debris Operating Committee
URL http://www.fraserbasin.bc.ca/_Library/Water/report_debris_trap_2006.pdf
Abstract/Description or Keywords This report summarizes the results of a preliminary cost benefit analysis of the Fraser River
Debris Trap. The debris trap is located in the Fraser River and on its north bank between
Agassiz (District of Kent) and Hope in British Columbia, Canada. The trap captures
25,000 to 100,000 m3 (approximately 600 to 2400 highway logging truckloads) of woody
debris during the annual spring freshet. Approximately 90-95% of the debris is of natural
Currently, the net cost of operation of the trap is approximately $640,000 per year,
including costs associated with the current funding approach, i.e., funds are raised for
the operation annually from a diversity of sources. Even with the trap in operation,
approximately 5000 m3 of waterborne debris is generated downstream in the lower
Fraser River. This study estimates that the annual cost to manage this amount of debris
and mitigate its impacts is approximately $1.59 million per year. Based on a
conservative volume of 25,000 m3 of debris captured by the trap per year, it is
estimated that if the facility were decommissioned, the amount of debris flowing into
the lower Fraser River – and the incurred costs to manage it – would increase by at least
six times to $9.55 million per year. This means that an investment of $0.64 million per year
results in at least $7.94 million in avoided costs per year for respondents interviewed,
resulting in net positive savings of $7.3 million. The net present value over 5 to 20 years of
the debris trap is $30 to $90.6 million when using discount rates of 10% to 4%. These are
conservative estimates as a low debris capture volume was used for the analysis, and
estimates of current debris management costs downstream of the trap are based
primarily on information from a limited number of survey respondents. In addition, costs
are likely to increase more than linearly with increasing debris volumes.
Information from survey respondents suggests that the various interests that directly
avoid costs through the continued operation of the trap include:
• Transport companies and saw mills (less damage to boats and barges, less cleaning of
debris from log booms) with at least a 40% share in total avoided costs;
• Municipalities and regional governments (less damage to dykes, seawalls, flood boxes,
drainage and other infrastructure, less beach clean-up) with a 24% share;
• Federal government agencies and Crown corporations (less habitat restoration required,
less damage to pilot boats) with a 19% share.
• Port and airport authorities (less cleaning up of harbour areas and foreshore
infrastructure) with a 13% share.
Furthermore, the debris trap helps avoid costs that are more difficult to quantify, for
• Dyke and seawall maintenance (less impact during storms)
• Personal injuries/fatalities (fewer accidents on the Strait of Georgia and the Fraser River)
• Foreshore property repair (less impact during storms)
• Pleasure boat repairs (fewer collisions with waterborne debris)
• Degradation of marshland (less smothering of sensitive marsh areas in the Fraser estuary)
• Log spills (fewer log booms failing due to impact of debris)
The debris trap ensures navigability of the Fraser River during the spring freshet. This
avoids negative impacts on revenues of the transportation and recreational sectors.
Because of the growing importance of these sectors in particular, and the doubling of
the population in the region by 2050 in general, the importance of the debris trap as a
cost avoidance measure is likely to increase in the future.
Information Type report
Regional Watershed Lower Fraser
Sub-watershed if known Fraser River
Aquifer #
Project status complete
Contact Name
Contact Email