METRO VANCOUVER - Combating rising sea levels due to global warming could cost $9.5 billion in flood-protection improvements in Metro Vancouver — including sea gates at False Creek and Steveston — by 2100, according to a report released Tuesday by the B.C. government.
The report, Cost of Adaptation - Sea Dikes and Alternative Strategies, covers the Metro Vancouver coastal shoreline and the Fraser River downstream of Port Mann Bridge — an area with more than 250 kilometres of shoreline.
The $9.5-billion cost estimate includes design, project management, land acquisition, environmental mitigation, impacts on utilities and pump stations and earthquake-resistant construction methods.
The Delcan report singled out three areas in the region for potential special protective measures:
- False Creek: A $25-million sea gate would allow the movement of water and boats through during normal water levels but would be closed during storm conditions to limit sea levels and reduce the height of shoreline defences needed around the perimeter of False Creek.
- Steveston: Use Shady Island as part of a breakwater/barrier with a sea gate to protect a densely developed waterfront with historic buildings at an estimated cost $10 million.
- Mud Bay, Surrey: Sea gates at the mouths of the Nicomekl and Serpentine rivers at a cost of $10 million each, along with a "managed retreat" or gradual decommission of development in the area.
Other options include: new or expanded dikes, including secondary dikes; floodwalls, made perhaps of concrete or steel where there is insufficient room for dikes; breakwaters or barrier islands to dissipate wave energy; greater restrictions, including building code standards, related to buildings in flood-prone areas; and better flood-warning and response systems.
Steve Thomson, Minister of Forests, Lands and Natural Resource Operations, said in an interview from Victoria that funding for diking projects tends to be shared by municipal, provincial and federal governments and he expects that to continue into the future.
"This is the start of a long and complex process," he added, noting that the level of flood-protection improvements will depend on the extent to which climate-change predictions come true.
Richmond councillor Harold Steves said he is aware of various flood-related proposals involving Shady Island dating back to 1969.
The city's latest concept is to in-fill the east end of the island for marsh habitat, forcing the Fraser River to flow around the south side of the island. A steel sea gate, common in Europe, could then be installed near the west end of the island connecting to Steveston, while earth sea berms could be built off Sturgeon Bank to break the storm surges, Steves said.
Co-funded by Natural Resources Canada, Cost of Adaptation is a follow-up to a 2011 report, Climate Change Adaptation Guidelines for Sea Dikes and Coastal Flood Hazard Land Use, which predicted a sea level rise of 1.2 metres along B.C.'s coast by the turn of the next century.
Seismic upgrades would be prohibitive on some stretches of dike, including on a total of 35 kilometres of dikes in Richmond and Surrey fronting the Fraser River, at more than $80,000 per metre. Options could include realignment of the dike, construction of a wide "superdike," or limited seismic ground improvement, the report found.
The decision to make large investments in flood protection infrastructure should be made within an overall Regional Flood Protection Strategy, and developed with the Province or regional body taking the lead, the report suggested.
Glenn Bohn, spokesman for Metro Vancouver, said the region currently has no mandate for diking.
Many of the region's dikes were constructed or upgraded during the Fraser River Flood Control Program which ran between 1968 and 1994, the report noted. These