Skip to content

North and South Thompson rivers could peak at same time

Such synchronicity in the past has led to significant flooding in the Kamloops area

The City of Kamloops says rain in the forecast could lead to the North and South Thompson rivers — both unseasonably high and on flood watch — peaking at the same time, as early as this weekend.

Both rivers peaking at the same time has led to significant flooding in the past.

The city has activated its emergency operations centre and some private properties have seen localized flooding due to thunderstorms that have recently rolled through the area.

“That worst-case scenario that we’ve been speaking about for a while — of the North and South peaking at the same time — is becoming more and more a possibility here,” city utility services manager Greg Wightman told reporters near the high-water marker at Riverside Park on Tuesday (June 21).

Tuesday marked the summer solstice, but spring freshet is behind this year, due to a cool spring and significantly more snow still in the mountains compared to normal. Typically, the mountains at this time of year are generally snow-free, but there is “a lot of snow left up in the higher level elevations left to come down,” Wightman said.

He said the city is expecting a 1999-level flood event as a possible high projection and continues preparing for the historic 1972 level. Both dates appear on that high-water monument in the park.

In 1999, water filled Riverside Park, while the 1972 flood led to a berm being breached in Westsyde, resulting in major flooding in the Oak Hills neighbourhood, with two youths drowning, in Tranquille Creek and in the McArthur Island lagoon.

The city has launched a level one (there are three levels and level one is more precautionary, with minimal staffing 24/7) emergency operations centre. Wightman said the North Thompson has potentially already peaked, but remains high due to the amount of snow still left in the mountains. The South Thompson is expected to peak toward the end of this weekend or early next week.

“That synchronization of the peaks looks like it’s going to happen this year and it’s just going to be a matter of how high those peaks are,” Wightman said.

It all depends on rain, which is forecast in the coming days.

“Environment Canada and BC River Forecast Centre are expecting some significant rain in the headwaters of the North Thompson River this week, Tuesday to Thursday, and potentially in the headwaters of the South, as well,” Wightman said. “And that’s what we’re monitoring right now. If that were to occur, we’re going to see a drastic spike in these rivers, potentially as much as a meter to a meter-and-a-half. Best-case scenario, those rainstorms don’t happen and the rivers will likely stay similar to levels to what they are right now.”

Wightman said an expected warming trend — Environment Canada is calling for the mercury to hit 29 C this Saturday before reaching 33 C on Sunday and Monday — is not as concerning and would, in fact, help to melt snow that remains in higher elevations at a manageable level, if the rain holds off.

Wightman is asking the public to be “hyper-aware” and do everything to protect private properties. City crews are protecting public property and critical infrastructure. Homeowners can pick up sandbags at Kamloops fire halls.

“Safety is going to be extremely important over the next week here as the rivers are flowing extremely high and we’re asking that everyone stay back from the rivers,” Wightman said.

He said the city is much more prepared for flooding today than it was in 1999, including a new dike being built in Riverside Park. Both Riverside Park and McArthur Island are protected to a one-in-20-year flood event, meaning it could withstand 1999 levels, but not 1972 levels.

The city built the new Riverside Park path like a road, with vehicles able to drive on it and capable of withstanding flood protection barriers, called Hesco baskets. The baskets were previously deployed on the grass in the park and required restoration work when they were removed.

On Tuesday, the pier remained blocked off, the pillars almost completely consumed by the river. A “danger” sign on wooden pole in the river that warns beachgoers where not to pass when swimming was also almost completely underwater.