Kootenay snowpack well above normal
Snowpack levels in the Kootenays are the second highest in 30 years, but forecasters say it’s too soon to tell whether spring flooding will result.
“The Kootenay snowpack is at 142 per cent of normal,” says David Campbell of the B.C. River Forecast Centre. “The last time we saw conditions like this was in 1991.”
Cool weather in April allowed for on-going accumulation of snow, and delayed the onset of the melt by about three weeks, he says, raising concerns for the southeast part of the province.
“In terms of specific flood risk, this shapes up one aspect of the puzzle,” Campbell explains. “We anticipate higher than normal volumes of water coming down through the spring freshet. Whether we get flooding is going to depend on weather conditions over the next month and a half.”
He says once the melt begins, the worst-case scenario is several days or a week of above-normal temperatures. The other combination is warm weather followed by heavy rain, which in and of itself could cause trouble.
“It does come down to the weather,” Campbell says. “We’re just starting to see the upswing of the melt at mid and low elevation. The upper elevation still hasn’t started to kick into melt yet.”
Bigger watersheds are still some ways from becoming concerns — right now, major rivers in the Kootenays are at below normal flows.
“I anticipate it’s going to be some time before we get primed up. The window we’re concerned about is the next couple of weeks to a month and a bit,” Campbell says.
He adds one big factor is the La Nina phenomenon, believed responsible for the cooler spring we’ve had. Those conditions are expected to continue for a few more weeks, which could delay peak flows and reduce the risk of flooding.
Meanwhile, City of Nelson engineering and operations director Allen Fillion says while they always watch creeks closely, there is added concern this year due to the higher snowpack.
“Any creek can become a problem because of a plugged culvert, but Anderson’s probably the primary one,” Fillion says. “That seems to be the most prone to flooding. Cottonwood’s more contained with a deeper channel and not as likely to flood.”
He says in 2006 there were high flows on Anderson, and a few places were sandbagged, but the creek did not actually flood. Since then, thanks to cooler springs and more drawn-out freshets, there haven’t been any close calls.
Anderson Creek typically peaks around the May long weekend, although will likely do so later this year, Fillion says. Public works crews monitor creeks daily, and more frequently as water levels rise.
“We keep kits handy if need to do something,” he says. “On Anderson Creek we have trash racks. Then we have equipment to dislodge rocks if too much debris starts piling up. We’re very vigilant about it.”
Fillion adds they can’t be everywhere all the time, and appreciate hearing from people if they spot any problems on city waterways.