Stubbornly cold weather is behind an increasing threat of ice jams on the Red River, provincial flood forecasters said today.
It’s been so cold, river ice remains 10 to 20 per cent thicker than normal for this time of year.
The threat is compounded by flood water coming up the Red from the United States where it is expected to meet solid river ice south of Winnipeg.
Three low-lying homes in St. Norbert will need to close off rings dikes around them and more homes could be put on the list if the threat of flooding rises in the next week. All homes at risk will be notified by the city.
Winnipeg flood-planning engineer Grant Mohr said the higher expected crest will require the construction of precautionary sandbag dikes around three Winnipeg properties - two on Cloutier Drive in St. Norbert and one on Kingston Row in St. Vital.
The city plans to contact the property owners over the next two days. The dikes will be in place by the weekend, Mohr said.
"They've had to sandbag in the past, so they're aware of what they have to do," he said.
Ice jams may begin to form on the Red within the city as early as Sunday, Mohr said.
Flood situation similar to 2009
The flood situation this spring is somewhat similar to 2009 when ice jams on the Red River north of Winnipeg caused sudden flooding of Breezy Point.
The 2009 flood was the fourth highest on the Red River in Manitoba since 1826.
However, what’s different this year is that there is a lot less water in the Red River Valley.
The Red River at Emerson is now expected to peak April 18 or 19 at a flow of approximately 35,000 cubic feet per second (cfs). The Red River upstream of the floodway inlet is expected to peak between April 20 and 22 at a flow of approximately 40,000 cfs.
It is estimated with an open-water crest, levels at James Avenue would reach 16.2 to 16.7 feet. In 2009, the crest was 22.5 feet.
However, if river ice does not break up, it could create a higher than normal crest producing a flow of 40,000 cfs, and a possible ice-induced crest of 18.2 to 18.7 ft. at James Avenue with approximately 5,000 cfs spilling naturally into the floodway channel.
The floodway cannot operate effectively unless the water and ice on the Red River is flowing freely as to reduce the chances of ice jams in the floodway and flooding.
Meanwhile, the Portage Diversion west of Portage la Prairie will continue to be operated to limit flows to 5,000 cfs along the lower Assiniboine River to minimize the risk of ice jams.