Springtime flooding weather dependent as snowpack continues to climb

By on February 19, 2018
The Nicola River circa April 2016. (Herald file photo)

The BC River Forecast Centre is expecting high flows down the Nicola River this spring, but Merritt receiving any substantial flooding will depend on the weather.

Dave Campbell, head of the BC River Forecast Centre, said flows in the Nicola River are expected to be about 155 per cent of normal this spring, but how fast the snow melts will determine if 2018 is another significant flood year.

“If you can draw it out over a long period then we won’t see flooding, but if it gets compressed [over a short period of time] or you add more water from rainfall then that can cause problems,” Campbell said.

The Nicola basin’s snowpack is a little more than a third higher this year than it was at the same time last year, Campbell said.

As of Feb. 1, the entire watershed is sitting at approximately 120 per cent of normal for this time of year, Campbell said.

“That’s something we’re watching pretty closely — starting to end up in that 120 per cent [range] is where we start to get a little more worried as we get into April,” he said. “I think the fact that we’re on that trajectory right now is definitely something to be watching.”

One measurement from the Coldwater side of the basin sits at about 143 per cent of normal while the one flowing into Nicola Lake sits at 102 per cent.

Campbell said the depth of water in the snow is in the 240 millimetre range at higher elevations for the Nicola basin. Last year that number was about 130 mm.

Last spring the Merritt area experienced a large flood due to a fast snowmelt combined with rain, but the snowpack itself was fairly modest until the end of the winter.

“Really it was the weather driving that,” Campbell said. “The snow tells us a little bit that that risk may be higher, but really it comes down to that weather piece as we get into late April, May [and] into June.”

With the snowpack already higher than last year, if there is a repeat of 2017’s springtime weather conditions, the flooding could be worse this year.

“That’s not necessarily what we’re expecting, but that’s a scenario that could play out,” Campbell said.

The numbers at the moment for the Nicola watershed are based on just two measurements, Campbell said, adding that in March and April there will be more data collected to provide a clearer picture.

“There’s probably at least another four or five that are within or very close to the watershed that get measured later,” Campbell said. “That’ll beef up those numbers.”

The River Forecast Centre analyses data collected by the Ministry of Environment.

“A team goes out to the field, they [have] a pipe, they put the pipe into the ground, they measure how deep the snow is, but they’ll also measure … how much water is stored in the snow at that location,” Campbell said. “That’s what we base our numbers on — percentages, per cent of how much we normally have.”

From those measurements, the River Forecast Centre knows how much water to expect.

Although there is still about a month left before snowmelt begins, Campbell said residents living along a floodplain can take precautions through seasonal planning, checking Emergency Management BC’s website for tips and contacting their local government.

One Comment

  1. AG

    March 5, 2018 at 8:01 pm

    Possible flooding worse than 2017? We haven’t even finished the repairs from the last flood!! I don’t know about you but if someone just used some logical thinking this could be controlled now rather than waiting to see what happens with the weather in March or April. If Nicola lake is at 102% why don’t you start letting out water now so that the run off can fill it up? I know I certainly wouldn’t mind not having to clean up after another flood that destroyed a lot of properties!!!

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