Archived News Releases

Second Spring Flood Outlook for Manitoba

Manitoba Water Stewardship’s second spring flood outlook shows the 2011 spring flood potential remains high for much of Manitoba including the Red, Souris, Pembina, Assiniboine, Winnipeg, Saskatchewan and Fisher rivers as well as the Interlake region.  Flood potential is high in these areas due to high river flows, very high soil-moisture conditions at freeze-up, above normal snow-water content in the snowpack, and an expected cooler and wetter spring. 

Additional snowpack in southern areas of the Red River basin indicates that river levels may be slightly higher than what was predicted in the January flood outlook.

Average weather conditions along the Red River could result in a flood higher than 2009 while unfavourable weather conditions could result in Red River water levels reaching those experienced in 1997.

With average weather conditions along other rivers and streams in Manitoba, flooding is still anticipated and, with unfavourable weather, significant flooding could occur.

The spring flood potential is still very dependent on weather conditions from now until the spring melt.  The amount of additional snow and rain, the timing and rate of the spring thaw and the timing of peak flows in Manitoba, the U.S. and other provinces will have a significant effect on flood potential.

Localized overland flooding is expected in most of central and southern Manitoba and could occur during the early part of the run-off period due to ice jams, snow blockages or frozen culverts in river channels, drains and ditches.

Climatic Conditions

• Precipitation during the autumn of 2010 was well-above normal in most of Manitoba, central and southern Saskatchewan, North Dakota and Minnesota.
• Cold temperatures from mid-November 2010 up to now have resulted in deeply frozen soil conditions in most areas.
• Widespread, heavy snow occurred from late November through early February in Manitoba, central and southern Saskatchewan, North Dakota and Minnesota.
• Recent warmer weather has slightly decreased the depth of the snowpack but the water content in the snow has remained relatively unchanged.  Most of the snow water is contained in the snowpack or near the surface layer and is expected to remain in place until the start of the spring thaw.

Both the Assiniboine and Red rivers main stem channels rose less than three centimetres (1.2 inches), indicating a minor flow from snowmelt run-off.

• The spring flood outlook is classified into three future weather scenarios related to additional snow, melt rates and spring rain.  These scenarios are based on available climate statistics for the past 30 to 40 years.
• The three future weather scenarios are referred to as favourable, average and unfavourable. 
• There is a one-in-10 chance of the weather being favourable and there is a one-in-10 chance of it being unfavourable.  The favourable and unfavourable scenarios assume that breakup will be slow and relatively fast, respectively.  Average weather and breakup conditions are assumed for the average scenario.
• Forecasts do not include effects of possible ice jams which are generally unpredictable.  Localized and brief flooding can occur in locations where ice jams develop, even with below-average river flows.

• • There is a one-in-10 chance of unfavourable weather.  With unfavourable conditions, peak stages would be comparable to or slightly higher than 1997 levels at most locations.
  • At most locations south of Winnipeg, Red River levels would not exceed those of 1997 by more than 30 cm (one foot).  Due to protective measures in place, it is unlikely that homes would be flooded even under unfavourable weather conditions.  However, transportation and access to properties in the flood plain would be reduced for up to three weeks.  The crest in downtown Winnipeg would be similar to 1997, with a maximum of about 7.47 m (24.5 ft.).
  • Peak stages from Selkirk to Breezy Point would depend on whether ice jams develop. 
    Ice-cutting and breaking operations will reduce the chance of serious ice jams.  Currently, ice buildup is slightly less than the winter average due to high river levels and substantial groundwater flows which typically contribute warmer water to the Red River.  With unfavourable weather, serious ice jamming will be reduced by ice cutting and icebreaking. 
  • Even without serious ice jams, flooding of low-lying properties in the Breezy Point area is likely.  Elsewhere, flooding is not expected unless serious ice jams develop.

Red River Tributaries

• With favourable weather from now through to spring, flooding would be fairly localized. 
• If average weather conditions occur, significant over-bank flows would develop on portions of most streams and there would be overland flooding in low-lying areas.
• With unfavourable weather, extensive over-bank flows would occur on all streams, bringing them close to 1997 levels.

Pembina River

• With favourable weather conditions, there is the potential for minor flooding.
• With average weather conditions, peak water levels along the Pembina River and tributaries would still be close to those of 2006.
• With unfavourable weather (one-in-10-chance), flooding could exceed that of 2009.

Roseau River

• With favourable weather conditions, minor flooding is expected.
• With average weather conditions, flooding would occur at close to 1974 levels.
• With unfavourable weather conditions, flooding would occur at close to 2002 levels.

Assiniboine River Main Stem

• Favourable Weather
  • With favourable weather conditions, there would be minor flooding along the Assiniboine River.
• Average Weather
  • With average weather conditions, there would be flooding along the Assiniboine River.  The drawdown of Shellmouth Reservoir now underway will minimize the risk of flooding while providing sufficient water supplies to meet downstream needs in 2011 and beyond.
  • Average weather conditions may also result in flooding from Millwood to Brandon with levels generally below those of 1995, but higher than 1979.
• Unfavourable Weather
  • Unfavourable weather would result in flooding of valley lands from Shellmouth to Brandon with levels likely higher than those of 1976 by about 0.05 to 0.6 m (0.2 to two ft.).
  • Shellmouth Reservoir is being drawn down this winter to provide maximum storage space for spring flood control along the Assiniboine River.  This will greatly reduce spring peak stages along the river, especially for the portion between the dam and St. Lazare, where flooding will be avoided only if favourable weather conditions occur.
  • The Portage Diversion will be operated to prevent ice jams and flooding from Portage la Prairie to Winnipeg.  Flooding may occur in this region with unfavourable weather conditions.

Assiniboine River Tributaries

• With favourable weather, localized flooding is expected.
• With average weather conditions, flooding is likely. 
• Unfavourable weather conditions would result in significant flooding on most tributaries leading to over-bank flows.

Souris River

• The flood potential is high for the Souris River due to high soil moisture and higher-than-normal snow cover in the North Dakota portion of the watershed.  Significant flooding of agricultural lands adjacent to the river is likely. 
• A favourable weather scenario would produce a flood similar to that of 2001.
• With average weather conditions, a flood slightly less than that of 1974 is likely.  Low-lying portions on the south edge of Melita would require diking.
• Unfavourable weather conditions would result in water levels higher than those of 1974 but lower than the peak stages of the 1976 record flood.  Low-lying homes near Souris would require diking in addition to the area next to PTH 3 at Melita.

Souris River Tributaries

• With average weather conditions, flooding is likely on Souris River tributaries. 
• Under unfavourable weather conditions, Souris River tributaries would experience significant flooding.                                                                                       

Interlake Region

• Soil moisture is well-above normal and most small depressions are relatively full from heavy rains last summer and fall.  Snow cover is currently average to above average.
• With favourable weather, flooding would be limited to low agricultural lands and streams would remain within their banks.
• With average weather conditions, flooding would occur and the Fisher River would see flood levels close to those of 2006.  Overland flooding would also occur.
• With unfavourable weather, flooding similar to 1986 (but lower than 2009) could occur.  There could also be difficulties due to a high water table, resulting in seepage into basements in rural areas. 
• Record high levels are likely on the Shoal Lakes, even with average weather conditions.

Eastern Region

• Soil moisture is currently above average and snow cover overall is above average in the region.
• With favourable weather conditions, localized flooding could occur on the Brokenhead, Whitemouth, Whiteshell and Winnipeg rivers.
• If average weather conditions develop, flooding is likely to occur along streams and lake shores.  The Winnipeg River could experience levels similar to those of 1994.
• Unfavourable weather conditions could result in flooding of agricultural lands that would be close to previous record floods.  In unfavourable weather conditions, water levels in the Winnipeg River would be similar to 2009 flood levels.

Westlake, Dauphin and The Pas Regions

• Soil moisture is above normal to well-above normal in most areas.  Snow cover remains generally near normal to above normal.
• With average weather conditions, flooding is possible on the Whitemud, Turtle, Swan and Carrot rivers.  With average conditions, the Saskatchewan River would be expected to see flood levels slightly higher than the 2005 flood at The Pas.
• With unfavourable weather conditions, general flooding could occur.  Brief localized flooding is also possible due to snow-blocked or ice-filled streams, drains or ditches.  If unfavourable weather conditions develop, flood levels higher than 1974 are expected on the Saskatchewan River at The Pas.