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Flood waters are seen from the air in Abbotsford, B.C., on Nov. 23, 2021.JONATHAN HAYWARD/The Canadian Press

The water that flooded the Fraser Valley of British Columbia’s Lower Mainland was disastrous – and also entirely predictable.

Reports on the risk of floods have clearly warned of vulnerable dikes. The warnings turned into reality in November, when an unprecedented deluge of rain hit. The Nooksack River, just south of the border in Washington State, flooded – and its waters spilled northward. Dikes failed around Sumas Prairie, 80 kilometres east of Vancouver. It put some of Canada’s best farmland under water – along with the Trans-Canada Highway, severing the Lower Mainland from the rest of the country. The estimated damage exceeds $1-billion.

The toll, however, is only a fraction of what could be truly calamitous flooding of the Lower Mainland. Mountains tower over the region but much of it, deep into the valley, is right at sea level, including Sumas Prairie, which was a lake until a century ago.

The risks of big floods come from both east and west. The Fraser River, from the east, recorded major floods in 1894 and 1948. With climate heating and rising sea levels, coastal flooding looms in the west.

In 2016, in a report for the Fraser Basin Council, the worst-case scenario was sketched out. It included failure of key dikes, and flooding on the scale of a one-in-500-year event – the size of the 1894 Fraser River flood. Costs of a coastal flood could hit about $20-billion, while a Fraser River flood could top $30-billion. The council called for preventive action, given “the chilling cost of inaction.”

But the Lower Mainland isn’t prepared. It’s the same across the country. Canadian cities garner a C+ grade for flood readiness, unchanged from five years earlier, according to a University of Waterloo assessment. Vancouver scored a C. Neighbouring Surrey got a B+.

A brief look at maps of the region’s dikes, coded for condition, shows scrawls of red and orange – unacceptable, or poor. In a major flood, the Fraser Basin Council reported that seven out of 10 dikes could fail, and less than one in 20 meet current standards. In Sumas Prairie, the height of a key dike that failed had been labelled unacceptable.

The costs of fixing the situation, never mind improving the defences, are high, but the costs of disaster are much higher. A top-end estimate to protect Sumas Prairie came in at $580-million. Long-term work on dikes in the Vancouver suburb of Delta could be $650-million. There’s no clear total for the Lower Mainland as a whole. The water in November flooded mostly agricultural land, along with key transportation routes. The costs and damage were relatively contained. If serious flooding hit from the Fraser or the ocean, the cost to residential properties alone could reach $7-billion.

In 2003, under the right-leaning BC Liberal government, the province tried to save money by forcing cities to figure out flooding on their own. After years of complaints, this will likely be reversed in 2022. As it stands, cities such as Richmond, almost all of it at sea level, try their best. The city of about 200,000 is surrounded by a 49-kilometre system of dikes. They are in variable condition but better than elsewhere. Vancouver has forecast an extreme weather event and sea level rise in 2100. If no mitigation measures are taken, Stanley Park could become an island, Granville Island would disappear, and the site of the under-construction $2.2-billion St. Paul’s Hospital would also be submerged.

In 2018, Ottawa started a disaster mitigation and adaptation fund; it topped it up in 2021, but the national total available is only $3.4-billion over about 10 years. B.C. has an advantage: Its fiscal position is arguably the best in Canada. The province could take on $10-billion of new debt today and still be in strong shape.

The to-do list is long, and it has been detailed in numerous reports of recent vintage. Prevention is one thing – almost all dikes need to be improved – but there are also difficult questions about land-use policies. Surrey and Delta are testing another strategy: a salt marsh on Boundary Bay – “a living dike” – to help absorb a coastal flood. There is also the question of the Nooksack River, a bilateral issue Canada hasn’t done enough to solve.

In the past, the aftermath of disastrous floods marked a short window when serious work was undertaken to mitigate the next inundation. The 2021 Fraser Valley flooding has to be the same, a clarion call. For the region, and for Canada. It will be expensive. But doing nothing will cost much more.

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