A higher, denser snowpack doesn’t guarantee spring flooding, but throw in some rain, or a quick melt, and there could be trouble
A higher snowpack across the central Prairies and northern United States will likely result in above-normal run-off this spring, but experts say flooding is not inevitable.
“The spring run-off is impacted by a variety of factors like moisture conditions in the fall, snow accumulation in the winter, as well as the rate of melt and amount of rainfall,” said Ken Cheveldayoff, Saskatchewan’s minister responsible for water security, in a release.
Manitoba’s western neighbour issued its spring flood outlook last week, and officials there said they will continue to monitor the situation as it develops. Manitoba’s first flood forecast is due this week.
Some areas of Saskatchewan have received twice the normal amount of precipitation this winter, while areas of Manitoba have also seen above-average snowfall.
News of predicted higher-than-normal spring run-off in the Assiniboine and Souris River basins has officials in western Manitoba paying close attention after many communities there experienced severe flooding in the spring of 2011.
Charlotte Parham, chief administrative officer for the Town of Souris, is cautious about overreacting to Saskatchewan’s flood outlook, but said town council is keeping a close eye on the situation.
In 2011, the town was forced to cut loose its historic swinging bridge over the Souris River to save the temporary dikes protecting the community.
The town of less than 2,000 residents has prepared for subsequent floods by revising emergency plans and implementing lessons learned in 2011. The CAO is also confident future flood forecasts will be able to better predict high water events. However, some pieces of the flood preparation puzzle are still missing.
“We’re still working with the province to construct a permanent dike system around residential areas and the sewage treatment plant,” said Parham.
That work is progressing slowly, and won’t be completed in time for spring should another flood be on the horizon, she said.
But it would take a series of weather events to create a flood like that seen in 2011, even with a higher, denser snowpack in Saskatchewan and Manitoba.
“The accumulation of snow is higher this year than last year, but the farmers say the ground is drier than it was in 2010, before we had the flood of 2011,” said Parham.
Meteorologist Greg Gust, with the American National Weather Service (NWS), agreed. He noted last summer’s dry conditions have left many rivers and tributaries in the region with below-normal water levels.
However, that may not be enough to prevent flooding south of the border, in the southern portion of the Red River.
In January, the NWS said the potential for flooding in Fargo, North Dakota was only at six per cent. Last week, the organization increased the risk of major flooding in Fargo to a 79 per cent chance.
But the Grand Forks-based Gust cautions against jumping to conclusions, noting flooding of the Red River in Fargo doesn’t translate into flooding north of the border.
“A big flood in Fargo… is something in the neighbourhood of 33,000 cubic feet of water per second, but a big flood in Grand Forks is three times that much water,” Gust said. “So if you bump up Fargo, it doesn’t mean that much when you get to Grand Forks, and by the time you get to Winnipeg, the contribution becomes less again.”
A 50 per cent increase to the flood risk in Fargo only results in a one or two per cent increase in Winnipeg, he said, explaining the Red River widens as it heads north, giving water more area to expand.
Manitoba had not released its 2013 flood forecast at the time of publication, but a spokesperson for Manitoba Conservation and Water Stewardship said the province has begin lowering water levels in the Shellmouth Reservoir in preparation for spring run-off from the west.
The annual ice-cutting effort has also begun on the Red River north of Winnipeg, as part of the province’s strategy to mitigate ice jams and related flooding.
“At between 24 and 30 inches, the ice is thicker than we’ve see in previous years,” said Premier Greg Selinger, adding the province’s ice cutters and Amphibex will work around the clock as the spring thaw approaches.