The Lower Mainland, including Langley, is vulnerable to a major Fraser River flood, according to a review by the Fraser Basin Council.
Rising sea levels and the impact of climate change are expected to make the risks of a major flood worse over the next 85 years, said the report.
“We now have a crisper picture of the evolving flood risk faced by the Lower Mainland and the chilling economic cost of inaction,” said Colin Hansen, Fraser Basin Council chair. “It’s time to kick into high gear, have all partners determine the best flood protection for the region, and roll out an action plan.”
The B.C. government announced $1 million Monday towards developing a flood action plan.
To put the possible worst case scenario into perspective, a catastrophic coastal flood could cost $19.3 billion or $22.9 billion on the Fraser River.
Those would be at least three times more costly than the 2013 Alberta floods that struck communities around Calgary.
The assumption of costs is based on each of the major flood protection dikes being breached and waters spreading freely.
Those worst-case scenarios have a 0.2 per cent chance of happening in any given year.
The analysis by the Fraser Basin Council found that most dikes in the Lower Mainland were built in the 1970s or 1980s. A full 71 per cent of the dikes may be susceptible to the water overtopping them during a major flood.
Only four per cent of the assessed dikes meet current provincial standards for height.
There have been several recent years in which high water has been on the minds of people living along Langley’s Fraser River shore.
In 2012, low-lying land in Glen Valley and near Fort Langley was underwater, including the basement of the Kwantlen First Nation band office on MacMillan Island.
In 2007, the entire Lower Mainland was on high alert as snowpacks were at 150 per cent of normal, while warm early June weather began the freshet.
There were plans to evacuate seniors from Simpson Hospital in Fort Langley, which was expected to be cut off from the rest of Langley if the water topped the dikes. Emergency responders held public meetings and organized plans to get people out of the flood zones.
A period of cool weather meant that the river topped six meters before receding, with the dikes still intact.
The most destructive flood of the last century was in 1948. The Fraser burst its banks and flooded low-lying portions of North Langley, briefly turning the Fort into an island. Matsqui, to the east, became a large lake.