The Red Sea south of Winnipeg could be one foot higher than the 2009 flood, the second worst in the last 50 years.
It means the precautionary evacuations of more rural residents — approximately 1,300 residents of 250 homes in the Red River valley and 800 Roseau River First Nation residents were uprooted in 2009 — and the potential for Highway 75 at Morris to be closed longer than the 36 days in that same year. The main route south to the United States was closed for 44 days in the historic flood of 1997.
The province will have a better idea of what areas face evacuation later today.
Flood forecasters in Manitoba blamed the upgraded flood risk on recent heavy snowfall in the U.S. that resulted in more precipitation than is normally seen in the entire month of April.
On Wednesday, the U.S. National Weather pegged the chance of a record flood crest at Fargo at 40 per cent, while Grand Forks and Pembina now have a 50 per cent chance of experiencing floods second only to the 1997 deluge.
Manitoba officials said the revised outlook indicates the river level could be half a foot to one foot higher than in 2009, which is significantly less than 1997 levels, from Emerson to Winnipeg. The flood peak is expected to hit Emerson in mid-May and Winnipeg a week later.
Typically, the flood peak in Winnipeg is in mid-April. The latest major spring flood crest for Winnipeg was May 19, 1950.
River levels at James Avenue in Winnipeg are forecast to be 17.7 ft. under favourable conditions, the province predicts. The number rises with poorer weather: 18.8 ft. James for average conditions and 21.5 ft. for unfavourable weather conditions. The 2009 peak was 22.5 ft. James.
Water levels on the Red River north of Winnipeg are likely to be close to those of 2009. The major issue that year was a significant ice-jam related flooding that destroyed more than 86 homes in Breezy Point, St. Clements and St. Andrews. The province has since bought those homes through a buyout program.
Grand Forks, Pembina and all Manitoba communities along the Red River are protected by floodwalls, levees or ring dikes built well above 1997 flood levels. Fargo, which has relatively little permanent flood protection, must raise its temporary dikes to protect against a crest as high as 42 feet. The record for Fargo, set in 2009, was 40.82 feet.
The outlook for flooding on the Assiniboine River has not changed. The flood risk in western Manitoba depends on how fast the record snow pack in Saskatchewan melts.
Premier Greg Selinger said Wednesday the Lake St. Martin emergency channel built during the 2011 flood could be called into service again this year depending on flooding.
"We’ve got equipment positioned there if necessary to open it up," Selinger said. "We’re doing all the preparations necessary."
The six-kilometre channel was built in late 2011 to lower water levels on Lake St. Martin to 801 feet above sea level, well below its 805.6-foot peak in July 2011, by draining excess water into Lake Winnipeg.
It was also used to lower Lake Manitoba to the south, which had reached a level of 817.15 feet above sea level during the height of the flood. The normal operating range for Lake Manitoba is 810-812 feet above sea level.
The channel was closed in late 2012.
The province says based on the Environment Canada long-range weather forecast, melt and subsequent runoff could start as early as this weekend, though it would require sustained warmer conditions with temperatures above freezing overnight.