Manitoba now trending toward 2009-scale flooding

Posted

Manitoba’s provincial flood forecasters now expect “moderate to major” flood risk this year, trending toward the levels seen in 2009 in the province’s Red River Valley and in the Interlake region between Lakes Winnipeg and Manitoba.

The provincial Hydrologic Forecast Centre’s second flood outlook for the year, released Tuesday, calls for increased spring flooding potential on the Red, Souris, Pembina, Assiniboine, Saskatchewan and Qu’Appelle rivers, and in the Interlake, due to additional March snowfall, aboveaverage snowpack in many parts of the province, and low temperatures keeping frost in the ground longer than normal.

That said, the forecasters added, the current outlook “does not foresee prolonged river flooding and high lake levels as in 2011.”

On top of the heavier-than-average snowfall — 200 per cent of normal in much of Manitoba, Saskatchewan and North Dakota this month — provincial forecasters now note coolerthannormal temperatures, which they said have increased the depth to which soil remains frozen.

Soil across southern Manitoba is frozen to a depth of between 50 and over 100 cm, mainly due to prolonged periods of very cold temperatures.

Colder-than-normal temperatures will also cause a later spring melt, thus increasing the likelihood of a rapid melt. Cool temperatures later into the year also make it more likely that the melting snowpack and normal spring rains will come at the same time.

All that said, “conditions can change quickly and the outlook is still very dependent on weather conditions from now until the spring melt,” the province said Tuesday.

Potential exists

Saskatchewan’s provincial Water Security Agency reiterated on March 11 that, based on the amount of snowfall this winter, an “above-normal” runoff is expected for the majority of the province, while some areas have the potential for “very high” runoff and flooding.

“The rate of melt and how much additional precipitation falls as snow or rain in coming weeks will determine the risk of flooding this spring,” Ken Cheveldayoff, the provincial minister for the agency, said when the province released its flood outlook March 11.

“However, if the precipitation conditions going forward are consistent with their historical averages, most of the province will experience an above average spring runoff.”

The U.S. National Oceanic and Atmospheric Administration’s (NOAA) National Weather Service last Thursday also forecast that the potential exists for “exceeding moderate and major river flood levels” on the Red River, which forms the state line between eastern North Dakota and northwest Minnesota leading up toward Winnipeg.

Similarly moderate and major river flood potential also exists on the Souris River in North Dakota for spring 2013, the NOAA said last Thursday. The Souris flows out of Saskatchewan into North Dakota and back into southwestern Manitoba, where it meets the Assiniboine southeast of Brandon.

These areas of North Dakota experienced “major to record” flooding in the spring of 2011, the NOAA noted.