Technology Science - Man. flood outlook worsens slightly

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An ice jam in Riverton, Man., forced the evacuation of 85 people from their homes in April 2009.An ice jam in Riverton, Man., forced the evacuation of 85 people from their homes in April 2009. (Photo courtesy Derek Bjarnason)

A major snowstorm that hit the northern U.S. earlier this week has escalated the risk of flooding in Manitoba.

However, the impact is not expected to be anywhere close to that being faced by Fargo, N.D., where the U.S. National Weather Service released its latest flood forecast earlier in the day and called for a 40 per cent chance of a record flood in that city.

In Manitoba, officials are still saying that with average weather conditions along the Red River valley south of Winnipeg, a flood slightly higher than 2009 is likely.

Unfavourable weather â€Â" a fast melt and above-average precipitation â€Â" could result in Red River water levels only slightly lower than the so-called Flood of the Century in 1997.

Many rivers, lakes to swell

The other major river in the province, the Assiniboine, is expected to flood along with its tributaries.

Forecasters said that with average weather, levels on the Assiniboine should be higher than during the most severe floods in recent memory: 1976 and 1995.

The Fisher River is also expected to flood, and a high water table in the area could also mean basement flooding.

The flood potential for the Souris River is also high, and low lying areas south of Melita, and near Souris will need diking.

The Shoal Lakes are expected to reach record high levels, even with average weather for the rest of winter.

A major storm hit the Dakotas, just south of Manitoba, on Tuesday.

More than 45 centimetres fell in the area and much of that snowmelt will drain into the Red River, which flows north into Manitoba.

"We have a lot of water to get through the system and it seems like it's all going to, probably, go at once," said Mike Lukes, hydrologist with the U.S. National Weather Service in North Dakota.

In some years, the spring melt is more staggered but it doesn't appear it will happen that way in 2011, he said, adding the major crest will likely occur in North Dakota in early to mid-April.

Lukes said the U.S. Army corps of engineers are working to protect the city.

"[They are] putting clay on the dikes and I think they have over two million sandbags filled already. So, you know, they are aware of the risk," he said.

Flood preps in high gear

The last flood outlook for Manitoba, released by provincial officials in February, called for water levels on the Red River to be 0.8 metres higher than during the flood of 2009 â€Â" provided the region experienced an average amount of precipitation up to the spring melt.

Unfavourable weather was likely to result in a flood as bad or worse than in 1997, forecasters said then.

The outlook on Friday is slightly worse, but not a whole lot.

Nonetheless, preparations for spring flooding are in high gear across much of southern Manitoba.

Wolverines cut grooves into the icy surface in early February.Wolverines cut grooves into the icy surface in early February. Sean Kavanagh/CBC

Ice on the Red River north of Winnipeg has been cut up after more than a month of operations.

Machines known as Wolverines began cutting 20-centimetre grooves into the icy surface in early February. Those grooves were then broken through by Amphibex machines.

The hope is to keep the ice flowing once the melt hits, and ward off jams that can cause havoc.

'We have the equipment spread out throughout the province, so we're out there doing what we can and we're not going to quit until mother nature forces us off the river.'

â€Â"Darrell Kupchick

In March 2009, the city of Selkirk declared a state of emergency after ice jams threatened to cause flooding in the city, 35 kilometres northeast of Winnipeg.

The following month, the swollen and fast-flowing Red River slammed into metre-thick ice jams south of Selkirk, forcing the water to jump the banks.

That created a flash flood that shoved large chunks of ice into riverfront properties in both the rural municipalities of St. Andrews and St. Clements.

The province's three Amphibex machines are now working to prevent ice jams elsewhere in Manitoba.

Teams are working on the Icelandic River in Riverton, the Portage Diversion and the Whitemud River near Portage la Prairie.

They plan to head to Brandon next, along with a number of smaller flood-prone communities.

"We're not out of the woods yet. We have the equipment spread out throughout the province, so we're out there doing what we can and we're not going to quit until mother nature forces us off the river," said Darrell Kupchick, who heads up a team of 30 people working on the ice.

Flood outlook summary

  • Spring flood potential in 2011 remains high for much of Manitoba, including the Red, Souris, Pembina, Assiniboine, Winnipeg, Saskatchewan and Fisher rivers as well as the Interlake region.
  • The flood potential is high due to above-normal winter precipitation, high river flows, very high soil-moisture conditions at freeze-up, above-normal snow-water content in the snowpack and an expected wetter spring.
  • Additional precipitation experienced in the southern areas of the Red River basin is expected to cause a slight increase in the river levels compared to predictions in the February flood outlook.
  • The spring flood potential is still dependent on weather conditions in the next few weeks until the spring melt begins.
  • The amount of additional snow and rain, the timing and rate of the spring thaw and the timing of peak flows in the U.S., Manitoba 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.

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