More Manitobans could be forced from their homes in the coming weeks due to what might be the worst flood in the Red River Valley since 1997.
The "Red Sea" south of Winnipeg could be one foot higher than the 2009 flood, the second-worst in the last 50 years.
Infrastructure and Transportation Minister Steve Ashton, the lead official on flood preparations, said Thursday the upgraded flood risk means the precautionary evacuation of more rural residents south of the city (250 had to leave their homes in 2009) and the potential for Highway 75 at Morris to be closed longer than 36 days, as it was in 2009. The main route south to the United States was closed for 44 days in the historic flood of 1997.
The province will soon have a better idea of what areas face evacuation, but most people in the Red River Valley who went through 1997 already know the lay of the land. Based on existing flood defences, none of the larger communities faces evacuation, as residents live behind flood walls, levees or ring dikes built above 1997 flood levels.
The heightened flood threat is due to a recent dump of snow in North Dakota that in a few hours resulted in more precipitation than normally seen in the entire month of April. The flood risk in western Manitoba remains unchanged despite a record amount of snow still on the ground in the Saskatchewan watershed of the Assiniboine and Souris rivers. Maps recently compiled by Environment Canada and other agencies show the majority of the Canadian Prairies and North Dakota still covered with snow, some more than a foot deep.
What has also heightened the flood alert is rain. With a rapid melt plus rain, flooding will come fast and furious.
"It's not in the forecast, but again, we are preparing for those possibilities," Ashton told reporters.
On Wednesday, the U.S. National Weather Service pegged the chance of a record flood crest at Fargo at 40 per cent. Grand Forks and Pembina now have a 50 per cent chance of experiencing floods second only to 1997 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 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, the year nearly 100,000 people were evacuated from their homes when the Red River flooded parts of the city. That catastrophe led to the building of the Red River Floodway. The floodway can only open up when Red River ice moves freely.
Officials point to 1995 as the one spring where there was as much snow still on the ground so late in the spring. That year was the third-worst flood on record along the Assiniboine River, after the floods of 2011 and 1976.
River levels at James Avenue in Winnipeg are now forecast to be 17.7 feet under favourable conditions, the province predicts. The number rises with poorer weather: 18.8 feet James for average conditions and 21.5 feet in unfavourable weather conditions. The 2009 peak was 22.5 feet 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 ice-jam-related flooding that destroyed more than 86 homes in Breezy Point, St. Clements and St. Andrews that April. The province has since eliminated that risk by buying out those homes.
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 the severity of flooding and how much water is funnelled through the Portage Diversion.
The six-kilometre channel was built in late 2011 to lower water levels on Lake St. Martin and Lake Manitoba to the south, which had reached a level of 817.15 feet above sea level at 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.
Based on the Environment Canada long-range weather forecast, the province says the melt and subsequent runoff could start as early as this weekend, though it would require sustained warmer conditions with temperatures above freezing overnight.