SEHAB Member: Brian Smith

Area: Port Moody to West Vancouver

Community Advisor: Sandie Hollick-Kenyon

Date: February 20, 2016

Key Issues:

What top three points can you distill from community input to take to DFO RHQ?

1.  DFO needs to provide core funding and technical support for the Seymour River Rock Slide Mitigation project.


A few examples of successes, failures, challenges.

At 5:30 am on December 7th 2014, a rock slide occurred within a canyon 0.5km downstream from the Twin Bridges crossing on the Seymour River in North Vancouver.  The slide deposited 50,000 cubic meters of rock into the canyon and temporarily blocked the Seymour River. The blockage created a dammed pool that varies from 13 to 25 meters deep, backwatering the river with the elevated water levels extending 600 to 1,100 m upstream of the slide depending on the river flow rate.  Precipitation due to storm events in the upper Seymour River resulted in two flood pulses releasing over the slide material on December 9th and 10th, 2014. These increases in flow mobilized and re-deposited finer rock slide debris downstream, resulting in settling of larger rock slide boulders into space created by the removal and re-deposition of the finer debris. Based on data collected after the rock slide event and assessment of the expected extent and frequency of inundation at the Twin Bridges upstream of the rock slide, Metro Vancouver proactively deactivated and removed the Twin Bridges crossing on January 12, 2015. Access to the slide site and Fisherman’s Trail were limited and the site was secured to limit public access and provide site safety.

The rockslide occurred approximately 14 km’s downstream of the dam and blocked fish migration through the slide area. The majority of productive spawning and rearing habitat for salmon lies upstream of the slide, while the downstream region is primarily developed land. The Seymour River is a designated wild coho, pink, chinook and winter and summer steelhead river. Steelhead are currently listed as a conservation concern due to results from a Provincial angling assessment of Seymour River steelhead (1983-present day). If fish passage is not re-established immediately, all salmon species and steelhead will likely be reduced to remnant populations as early as 2019. Pink, chum and Chinook salmon also access their spawning and rearing habitats through the slide area. While some spawning does occur below the slide for these species, their populations could also be significantly reduced within the same time frame.

Many of the plants and animals of the surrounding ecosystem rely on salmon as a food source and supply of marine-driven nutrients. Without the restoration of migrating fish to the affected area, these organisms could be significantly impacted. We strongly believe that the Seymour River is a stream at risk.

The goal of the Seymour River Rock Slide Mitigation Project is to restore fish passage through the rock slide, thereby reducing habitat fragmentation and loss and reducing the threat of stream degradation / ecosystem health. The objective of this project is to re-establish fish passage by use of low velocity explosives to beak down the slide debris, and high water events to wash the broken-up material down stream. This is the safest, most natural and least invasive method for workers, river users, and ecosystem inhabitants. This work will be an iterative process based on safe instream work opportunities immediately prior to high-water events. It is estimated that each rock-breaking opportunity will occur over a 4-7day period, 6-10 times per year until acceptable water flows and fish passage are restored. 

Until passage is restored, a floating fence will be placed closer to the mouth of the river in order to capture fish before they become trapped below the slide. The fence also has the potential to provide high-precision stock assessment data which will be used in conjunction with fish monitoring data collected from the slide once work commences.

The ultimate measure of success for this project will be the restoration of water and fish passage at low water levels.  During the summer and fall of 2015, radio and acoustic tags were applied to both upstream-migrating adult coho and steelhead and downstream-migrating steelhead smolts. Receivers were placed at either end of the slide debris to track the movement of the tagged fish. Movement will continue to be monitored on all receivers in conjunction with visual stream surveys of rearing and spawning habitat. Application of radio tags to semelparous adults will continue as individuals return to the Seymour River. Success will be determined by the percentage of tagged individuals that are able to move past the slide and by the presence of spawning adults visually confirmed above the slide.

The project is not a quick fix and it is not cheap:

  • One day = $5,000 - $7,000 (including materials)
  • Per event (5-day work period) = $30,000
  • Per Year (assuming 8 work events) = $240,000
  • Total (5 Years) = $1,200,000

Obviously this project is too large a scope for a community based not for profit organization to be responsible for.  We are asking SEHAB to help us convince DFO that they must lead and fund this project. 

Issues Specific to SEHAB’s Work Plan:

SEHAB Work Plan

Local Issue, Specific  Examples

Actions by Community or DFO

SEHAB Opportunity

Wild Salmon Policy (Stock Assessment, Habitat)








Capacity & Core Funding

Seymour River Rock Slide Mitigation Project

DFO to provide core funding and Technical support for the Rock Slide project.

Advise DFO to provide the required financial and technical support required for the Seymour River Rock Slide Mitigation Project

Submissions, Comments from Groups:

No submissions/comments from groups received.