Excessive snowpack and high water levels put communities in the Northwest Territories at risk of flooding again this spring.
This includes Hay River, Kátł’odeeche First Nation, Nahanni Butte, Fort Liard, Fort Simpson, Aklavik, Fort Good Hope, Tulita and Jean Marie River First Nation.
The Government of the Northwest Territories released a technical report on Monday indicating that there is potential for spring break-up flooding once again this spring.
This comes after devastating flooding last year left many homes damaged or destroyed in several communities across the Northwest Territories.
In an email outlining key takeaways from the report, the territorial government said ice jams during breakup can cause flooding regardless of water levels. However, high water levels increase the severity of floods.
High risk on Hay, Mackenzie, Liard and Peel River
Water levels in the Hay River Basin are at the highest level on record for or near this time of year, up to 40% higher than normal levels in Alberta and British Columbia.
This is combined with an already saturated soil which increases the risk of overflow of small water bodies.
Higher than normal water levels have been recorded around Aklavik and heavy snow accumulation is reported around the Peel River and the Mackenzie Delta.
The snowpack around the Liard River, which was the main cause of flooding last year in Fort Simpson, is about 56% above normal.
Throughout Dehcho, Sahtú, and the Beaufort Delta, there is a risk of flooding from ice jams on the Mackenzie River, which could be exacerbated by high snow volumes in the region, as well as high snow levels. water and an above average water flow in the river.
Unpredictable but not inevitable ice jams
Although water levels and snow accumulation can increase the severity of flooding, ice jams are the main cause of flooding during breakup, which is unique to the North.
And ice jams are hard to predict.
Ryan Connon is a hydrologist with the territorial government.
He said there are two ways ice can break up – there’s the “good way” or thermal, where the sun slowly melts the ice. Then there’s the wrong, mechanical path when there’s thick ice near communities at risk of flooding and rapid snowmelt in other parts of the basin, which quickly moves downriver.
“What it will do is it will push the ice to the edges of the banks and it will break up the ice a bit and when those big chunks of ice move further downstream and if they hit thick solid ice that doesn’t didn’t melt though, that’s how you get the ice jams,” Connon said.
It’s unclear if any ice jams will form until the breakup begins, which he predicts will occur in the next week or two.