Dikes require big-ticket upgrades to hold back sea

Report flags seismic risks, possible 'retreat' from some areas

Diagram showing latest design standard changes for sea dikes.

Rising sea levels will force major upgrades to the Lower Mainland’s expansive network of dikes in the coming decades, according to a provincial government report.

The newly released findings estimate dike upgrades could cost $9.5 billion over the next 90 to 100 years to prepare the Metro Vancouver area to withstand a significant increase in ocean levels as a result of climate change.

The report, titled Cost of Adaptation – Sea Dikes and Alternative Strategies, examined 250 kilometres of ocean shoreline from West Vancouver to White Rock and on the Fraser River as far upstream as the Port Mann Bridge.

It’s a follow-up to a 2011 report that predicted a one-metre rise in sea level along the B.C. coast by the end of the century.

Actual construction of larger dikes or other protective structures would be a small $880-million slice of the overall cost estimate.

A larger chunk is $1.6 billion for property acquisition, much of it in areas where taller dikes will require larger footprints, encroaching on adjacent land.

But the biggest cost component is an estimated $3.25 billion for seismic upgrades – more than half of the $6.3-billion overall cost before a 50 per cent contingency is added.

One of the risks flagged in the report is that an earthquake could cause some soil layers underneath dikes to liquefy, threatening their integrity.

The proposed changes take into account not just the sea level rise but land subsidence, maximum high tide, storm surge, wave effects and the need for freeboard.

Not all areas of low-lying land threatened by the ocean would be defended.

The report calls for a strategy in some flood-prone areas of “managed retreat” where currently developed areas are decommissioned over time and returned to a natural or low-value state that can flood periodically.

“Managed retreat may be a viable option at Mud Bay [in Surrey],” it says.

“However, the decision to retreat is complicated and would have to be made with extensive stakeholder input and economic analyses.”

Also contemplated are $10-million sea gates at the mouths of the Serpentine and Nicomekl Rivers, as well as a $25 million sea gate that could be closed during storms to protect Vancouver’s False Creek area.

Steveston’s densely developed waterfront of historic buildings might be protected by using Shady Island and a new sea gate as a storm surge barrier.

The report also considered the value of property and buildings in areas of Metro Vancouver – as well as social and environmental factors – as part of deciding whether expensive flood-protection works are justified on a cost-benefit basis.

The report also suggests a Regional Flood Protection Plan be drawn up with the province, municipalities and other agencies participating.

Developers are already recognizing the need for change.

Norm Shearing, vice-president of Parklane Homes, told a Metro Vancouver forum last month plans for the new River District residential area in Vancouver along the Fraser River were revised at huge expense to meet higher flood plain requirements.

“It was a thing we had to do to protect ourselves from the future,” Shearing said.

“The implications of sea level rise on the region and the engineering solutions that are going to have to occur is huge, it’s enormous.”

Just Posted

Delta mosque part of open-house effort launched in wake of New Zealand shootings

The ‘Visit a Mosque’ campaign aims to combat Islamophobia

White Rock dog poop conspiracy picks up steam

Opponent says theory is a ‘load of crap’

Surrey MLA slams NDP poverty reduction strategy plan

Liberal MLA Marvin Hunt says the NDP’s poverty reduction plan is ‘underwhelming’

Father thanks Surrey Mountie for shooting hoops with kids, ‘changing perspectives’

‘We’re just like everyone else,’ says Surrey officer who stopped to play basketball with kids

Noted Spanish guitarist in Surrey with VSO and Rodrigo’s ‘beautiful concerto’

‘I love playing it,’ Pablo Sáinz Villegas says of famous composition ahead of Bell concert date

Five highlights in the 2019 federal budget

Latest budget includes a sprinkling of money for voters across a wide spectrum

Facebook to overhaul ad targeting to prevent discrimination

The company is also paying about $5 million to cover plaintiffs’ legal fees and other costs

Teacher reprimanded after incident with Grade 11 student in school gym

Gregory Norman Brock was teaching at a high school in the Maple Ridge-Pitt Meadows School District

Explosives unit brought in after suspicious boxes left at B.C. RCMP detachment

Nanaimo RCMP issues all clear after packages were found on lawn earlier in the day

Avalanche control tomorrow on Highway 1

Expect closures of up to two hours east of Revelstoke

Newfoundland man caught after posting photo of himself drinking and driving

The 19-year-old took a photo of himself holding a beer bottle and cigarette while at the wheel

2019 BUDGET: As deficit grows, feds spend on job retraining, home incentives

Stronger economy last year delivered unexpected revenue bump of an extra $27.8 billion over six years

Carfentanil found in 15% of overdose deaths in January: B.C. coroner

Carfentanil is 100 times more powerful than illicit fentanyl and used to tranquilize elephants

Kids found playing darts with syringes in Vancouver Island park

Saanich police is urging people to throw out their syringes properly and safely

Most Read