Fraser River during the high water of 2012.

Fraser River during the high water of 2012.

Growing risk of devastating flood in Lower Mainland from climate change: report

Most dikes along Fraser River do not meet modern standard, Fraser Basin Council finds

Vast sections of dike that hold back the Fraser River in the event of a major flood are at risk of failing, unleashing a devastating flood that could cause losses of more than $20 billion.

That’s the stark warning in a new series of reports and flood maps released Monday by the Fraser Basin Council, which says the region is at risk of suffering the worst natural disaster in Canadian history.

The agency continues to lead a multi-phase initiative to assess and respond to the risks of Fraser River flooding and coastal flooding from storm surges.

Climate change is amplifying both threats, according to Fraser Basin Council senior program manager Steve Litke, because of projections of sea level rise requiring higher dikes to protect coastal areas, and now new forecasts that a flood along the lower Fraser is becoming more likely.

MORE RESOURCES: Fraser Basin Council maps and reports

That increased probability of an “extreme” river flood is due to warmer spring temperatures that can cause a fast melt-off of alpine snowpack, coupled with heavy rains, according to the Lower Mainland Flood Management Strategy report.

“We’re not as well protected as we thought we were,” Litke said. “Both coastal and river flooding is anticipated to increase in frequency and magnitude going forward.”

The aim of the agency is to develop a blueprint for deliberate, planned upgrades starting in 2018 to help avoid a repeat of 2007, when the Fraser threatened to flood and politicians frantically dispatched hundreds of dump trucks to raise dikes as an emergency action.

“We dodged a bullet,” council chair Colin Hansen said of that near-flood. “The waters of the Fraser River came within half meter of breaching the dikes that year.”

The council’s new analysis of current preparedness rated 69 per cent of dikes in the Lower Mainland as fair to poor, 18 per cent as poor to unacceptable, and 13 per cent as fair to good.

Only four per cent of dike segments assessed meet current B.C. standards for dike crest hike, which calls for 0.6 metres of freeboard above the water surface in a repeat of the 1894 flood of record for the Fraser.

Seventy-one per cent of assessed dikes are vulnerable to failure by overtopping in either a major river or coastal flood, consultants found.

Quakes also a dike threat

A large number of dikes aren’t just too low, they are also seismically vulnerable, because they were built years ago to outdated earthquake standards. In many cases, underlying soils near the Fraser are vulnerable to liquefaction in a quake, potentially compromising the dike.

Work to improve dikes is expected to be a multi-decade projects with vast costs.

Some flood defense improvements have already been funded by the province but much more is required.

There’s no detailed breakdown yet of what sorts of new projects would be required along the Fraser River, or the timeline or cost-sharing mechanisms for getting them built. That’s the next phase of work the council is planning.

A 2012 study on the costs of climate change adaptation provided a rough estimate of $9.5 billion in work required to raise or stabilize dikes just to deal with the coastal threat from sea level rise in the Lower Mainland.

Fraser Basin officials admit a key risk is whether or not they can hammer out an agreement among local governments and the province to embark on critical work as quickly as they’d like, particularly in light of intense pressure to fund other infrastructure priorities.

A coordinated regional strategy is needed for any work done because flood water that’s pushed back by higher dikes in one area will flow to another.

To dredge or not?

It’s not yet clear whether dredging will be one tool used to reduce the ever-increasing amount of gravel in the riverbed, and ease the resulting risk of flood.

“It’s a very polarizing issue,” Litke said, adding dredging will be examined as a potential option to remove gravel.

“We want to take out what’s coming in annually so we maintain the capacity of the river channels,” he said, adding the region needs to avoid a scenario where dikes must be raised ever higher.

“But we want to be very careful about how we do that. We don’t want to destabilize the river channel. We don’t want to create a new problem for any neighbouring community. And we certainly want to be cognizant of the environmental impacts, what’s the right timing and location.”

What isn’t under consideration is any emergency strategy where dikes might be deliberately breached in a high water scenario to allow water onto certain areas of farmland to reduce pressure on dikes elsewhere.

“There’s no huge benefit from sacrificing one area to save another,” said Neil Peters, B.C.’s former inspector of dikes, who added that would provide only a brief window of relief before the sacrificed area was full of water. “It isn’t a strategy that has been considered.”

The volume of water moving in the Fraser at flood level is enough to fill seven Olympic swimming pools every second.

To view the Fraser Basin Council flood maps and reports, see floodstrategy.ca.

DEFINING AN EXTREME FLOOD

A flow of 16,500 cubic metres per second flowing in the Fraser River at Hope is currently considered the 1-in-500 year flood, with a 0.2 per cent chance in any given year.

By comparison, the huge flood of 1894 – the Fraser’s flood of record – was estimated at 17,000 cubic metres per second.

By the year 2100, as climate change impacts grow, the 1-in-500 year flood could have a peak flow of 19,900 cubic metres per second, an amount now considered a 1-in-5,000 year event.

A major flood today would overtop dikes in multiple areas and inundate nearly 100,000 hectares of land.

Transportation links would be cut off with major highways underwater and food and other supplies could dwindle in as little as four days, according to the new Fraser Basin Council report.

More than 650,000 tonnes of debris would be floating on the floodwaters.

The tide of destruction would bring significant environmental contamination from chemicals, fertilizers, petroleum and raw sewage released by various compromised industries, treatment plants, and hazardous waste storage sites.

The report estimates 690 buildings would be destroyed in such a flood today, and 3,600 would be damaged, with building losses of around $9 billion.

Hospitals, police or fire stations and schools would be among the losses.

An estimated 266,000 people would be displaced and seeking shelter.

A major Fraser River flood today would result in total losses of $22.9 billion, the report estimated, and that could hit $32.7 billion by 2100.

A coastal flood from an ocean storm surge could result in losses of $19.3 billion, climbing to $24.7 billion by the end of the century.

Just Posted

Brandon Hobbs (turquoise shirt), brother of missing Abbotsford man Adam Hobbs, gathers with other family and friends to distribute posters in Chilliwack on Thursday, June 17, 2021. (Jenna Hauck/ Chilliwack Progress)
Search efforts expand to Chilliwack and beyond for missing Abbotsford man

Family, friends put up posters in Chilliwack, Agassiz, Hope for missing 22-year-old Adam Hobbs

A CH-149 Cormorant from 442 Transport and Rescue Squadron out of CFB Comox on a training exercise in Chilliwack on June 16, 2021. (William Snow photo)
VIDEO: Military search and rescue training in Chilliwack Wednesday

CH-149 Cormorant and CC-115 Buffalo from CFB Comox participated in downed aircraft rescue simulation

Stock photo by LEEROY Agency from Pixabay
Drop-in vaccination clinics slated in Abbotsford for construction workers

Among three sites in Lower Mainland holding no-appointment clinics in June and July

Linnea Labbee outside the Chilliwack Law Courts on April 1, 2021 on day 16 of her trial in BC Supreme Court. Labbee was convicted April 12 for the fatal hit-and-run of 78-year-old Fourghozaman Firoozian on Dec. 1, 2016. (Paul Henderson/ Chilliwack Progress)
Sentencing hearing scheduled for 72-year-old Chilliwack woman found guilty in fatal hit-and-run

Crown will seek jail time for Linnea Labbee who struck and killed 78-year-old woman in 2016

Chilliwack Spartans Swim Club coach Justin Daly.
Chilliwack Spartans swim coach Justin Daly wins Rubber Boot Award

Daly was recognized in a vote by fellow coaches in the BC Swim Coaches Association

People line up to get their COVID-19 vaccine at a vaccination centre, Thursday, June 10, 2021 in Montreal. THE CANADIAN PRESS/Ryan Remiorz
Vaccines, low COVID case counts increase Father’s Day hope, but risk is still there

Expert says people will have to do their own risk calculus before popping in on Papa

Helen Austin performing with Trent Freeman at the 2018 Vancouver Island MusicFest. Austin is one of the many performers listed for the 2021 event.
Vancouver Island MusicFest goes virtual for 2021

Black Press to stream 25 hours of programming July 9-11

FILE – A science class at L.A. Matheson Secondary in Surrey, B.C. on March 12, 2021. (Lauren Collins/Surrey Now Leader)
Teachers’ union wants more COVID transmission data as B.C. prepares for back-to-school

BCTF says that details will be important as province works on plan for September

Provincial health officer Dr. Bonnie Henry outlines B.C.’s COVID-19 restart plan, May 25, 2021, including larger gatherings and a possible easing of mandatory masks on July 1. (B.C. government photo)
B.C. records 120 new COVID-19 cases, second vaccines accelerating

Lower Pfizer deliveries for early July, Moderna shipments up

A Heffley Creek peacock caught not one - but two - lifts on a logging truck this month. (Photo submitted)
Heffley Creek-area peacock hops logging trucks in search of love

Peacock hitched two lifts in the past month

The Calgary skyline is seen on Friday, Sept. 15, 2017. THE CANADIAN PRESS/Jeff McIntosh
2 deaths from COVID-19 Delta variant in Alberta, 1 patient was fully immunized

Kerry Williamson with Alberta Health Services says the patients likely acquired the virus in the hospital

The first suspension bridge is the tallest in Canada, with a second suspension bridge just below it. The two are connected by a trail that’s just over 1 km. (Claire Palmer photo)
PHOTOS: The highest suspension bridges in Canada just opened in B.C.

The Skybridge in Golden allows visitors to take in views standing at 130 and 80 metres

BC Green Party leader and Cowichan Valley MLA Sonia Furstenau introduced a petition to the provincial legislature on Thursday calling for the end of old-growth logging in the province. (File photo)
BC Green leader Furstenau introduces old-growth logging petition

Party calls for the end of old-growth logging as protests in Fairy Creek continue

B.C. Premier John Horgan leaves his office for a news conference in the legislature rose garden, June 3, 2020. (B.C. government photo)
B.C. premier roasted for office budget, taxing COVID-19 benefits

Youth addiction law that triggered election hasn’t appeared

Most Read