With walls, berms and raised roads, Fort McMurray is working to keep its river from overflowing
CBC
Ever since the devastating spring floods of 2020 in Fort McMurray, the northeastern Alberta community has been shoring up its defences against rising rivers.
Now, officials with the Regional Municipality of Wood Buffalo (RMWB) say Fort McMurray is better prepared for future floods.
"From a permanent structural mitigation standpoint, there's been significant works completed," said James Semple, manager of RMWB's project management office.
It has spent $119 million on flood mitigation so far; the remaining work that is planned will bring the total expenditure to about $270 million, according to a statement on the RMWB's website.
Semple said the aim is to prepare the community for another one-in-100-year flood — which is what Fort McMurray experienced in 2020 — as well as a one-in-200-year flood, in which the river would rise by another half-metre or so.
Preparation means damages to residents and businesses would be appropriately mitigated, he said.
Fort McMurray sits at the confluence of the Athabasca and Clearwater rivers. When ice on these two rivers breaks up in the spring, it can create literal dams in the river. As water backs up, it eventually overflows the banks and can flood low-lying parts of town.
Ice jams tend to form downstream of Fort McMurray, where the Athabasca changes shape, said Nadia Kovachis, a river hydraulics and ice engineer with Alberta River Forecast Centre.
"The river really flattens out, which encourages sediment deposition, and this causes the river to be wider, with many more sandbars and islands. And these things kind of all work together to encourage ice jam formation," she said.
Fort McMurray has a long history of spring floods caused by ice jams on the Athabasca River, with records of extreme incidents going back to 1835. Of 17 notable floods since then, 16 were caused by ice jams.
The 2020 flood was caused by a massive 25-kilometre ice jam on the Athabasca. Water from both rivers spilled into downtown, forced about 12,000 people from their homes and caused more than $520 million in insured damage.
After the 2020 flood, an engineering report found that the municipality's flood mitigation system was incomplete and flawed.
Kovachis said it's difficult to predict when ice jam flooding will happen. That's why the mitigation measures are so important.
In September, the RMWB council approved going ahead with structural mitigation between the Clearwater River and nearby Clearwater Drive. This work is the final phase of permanent flood mitigation efforts for downtown Fort McMurray, the municipality said.
