Erosion arcs on the bank of the Fraser at Matsqui Prairie.

Erosion arcs on the bank of the Fraser at Matsqui Prairie.

$8M solution floated to prevent ‘catastrophic’ flooding of the Fraser

Erosion threatening riverbank; new study cites defenses

Every year, the southern banks of the Fraser River erode closer to the dikes protecting the Matsqui Prairie floodplain.

The city has a plan to stop it at the cost of $8 million.

A year-long, $180,000 study found a deepening pattern of “erosion arcs,” where strong currents chew into soft silt at the bottom of the riverbank. If any were to wear deep enough to breach the Matsqui dikes, it could trigger a catastrophic flood estimated to cause over $2 billion in damage.

“I think we are playing with fire,” said Mayor Henry Braun.

Northwest Hydraulics, a consulting firm hired by the city, found the erosion is ultimately caused by sediment carried from upstream. As that sediment expands the Sumas and Matsqui bars in the middle of the river, water flow is redirected and pummels the banks. If nothing is done, erosion will accelerate.

The consultants recommended building an array of rock spurs underwater at the river’s edge, to redirect the flow. The project would cost $8 million in total, phased in over eight years. The city approved this recommendation last Monday. Now the only issue is lobbying for provincial or federal funding for all or part of the project’s cost.

“This is not something that can be funded out of property taxes,” said Braun.

Matsqui Prairie, one of Abbotsford’s major agricultural areas, lies on a Fraser River floodplain protected by a series of dikes. Past failures of the dike system, in 1894 and 1948, caused devastating floods. Since then, farming in the area has intensified and industrialized, and a future flood would risk loss of life and deal a serious economic blow to the region. The area flooded would include Highway 11, multiple railways, the JAMES wastewater treatment plant, a military communication centre, agricultural processing facilities and residential areas.

In 2013, an erosion arc came within 30 metres of one of the dikes, prompting an emergency repair that cost nearly $3 million. While funding can be accessed quickly for emergency repairs, money for preventive measures takes more bureaucratic wrangling.

Two new arcs have emerged since the 2014 emergency, bringing their total number to six since 1997. Currently, the closest arc sits at 55 metres from a dike, resulting in the closure of a section of the Trans-Canada Trail, which runs along the river in that area.

Coun. Dave Loewen noted that recent dike upgrades have cost over $11 million, with more than half coming from city coffers.

“I just find it unconscionable that we, our taxpayers, should be paying the majority of this cost,” Loewen said.

The overall state of the dike system across all Fraser River floodplains in B.C. is understood to be poor, with a provincial report from 2014 noting that “most of the existing dikes do not meet the current minimal provincial standard, and would only provide protection against smaller flood events.”

As the riverbank is the traditional fishing territory of the Sumas First Nation, consultation would be required before building could begin. Another possible option for halting erosion armoring the bank with rocks was rejected partly because it could snag Sumas fishing nets.

Stephen McGlen, the Sumas First Nation lands and resource manager, said past consultation about alterations to the riverbank has been “inadequate,” and he hopes the situation will improve in the future.