The Hydrologic Forecast Centre of Manitoba Infrastructure and Transportation preliminary 2013 spring flood outlook suggests there could be a risk of minor to moderate spring flooding for the Red, Souris, Pembina and Assiniboine rivers, and in the Interlake region.
Above-average snowpack with high moisture content in many parts of Manitoba, Saskatchewan and North Dakota have increased the potential for flooding this year, but overall low soil moisture levels in the province mean the flood risk in 2013 is, at this point, considerably less than in 2011 and moderately higher than in 2012. At the time of freeze-up in 2012, soil moisture levels were significantly lower than the unprecedented and wide-spread wet conditions seen in 2010 prior to the major 2011 floods. At that time, there were high soil moisture levels at freeze-up followed by heavy precipitation in winter and spring.
Spring flooding is also likely in portions of northern Manitoba including overland flooding in the agricultural area around The Pas, where there are both above-average soil moisture conditions and significant snowfall this season. At this point, it is unlikely the Saskatchewan River at The Pas will exceed its banks, however the province has constructed new dikes in the area that are capable of taking water levels beyond levels seen in 2011.
The spring flood potential is still 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 the U.S., Manitoba and other provinces will have a significant effect on flood potential.
Though it is impossible to predict the occurrence or extent of ice jamming, ice-cutting and Amphibex icebreaking activities should limit ice jam-related flooding on the lower Red River. The Amphibex fleet has already broken a six-kilometre channel down the center of the river and 12 km of ice has been cut. The Amphibexes can be quickly deployed to break up ice jams on other rivers on an emergent basis as they were in 2011 when they were deployed to the Assiniboine River. The chances of minor localized flooding due to snow blockages in drains, ditches and small streams during the early part of the run-off period will be dependent on the nature of the spring breakup and rate of melt.
To address potential high water flow from Saskatchewan’s above-average snowpack, there has been a controlled release of water from the Shellmouth Dam since February. This will increase its reservoir capacity by approximately 10 feet.
The Portage Diversion operating guidelines allow it to be used for three objectives: minimizing the volume of water diverted to Lake Manitoba, protecting the city of Winnipeg or preventing ice from jamming on the Assiniboine River east of Portage la Prairie. The diversion has been used to prevent ice jamming every year since its construction and, under this year’s medium-to-moderate flood scenario, it will likely be again.
The Fairford Channel has been operating at full maximum discharge since fall 2010, drawing down Lake Manitoba to its current level of 811.8 ft. above sea level, which is well within the operating range of 810.5 to 812.5 ft. and its historical long-term average level of 812.12 ft.
The Manitoba government and municipalities are busy preparing for the potential of spring flooding. In the last few months there have been more than a dozen training sessions with municipal emergency management staff. The Manitoba government and its municipal partners are reviewing existing emergency response plans. Flood preparation will continue into the spring with more focused regional meetings and conference calls. The province is in discussion with Aboriginal Affairs and Northern Development Canada to ensure that First Nation communities are also prepared for potential flooding.
The geographical scope and duration of the 2011 flood was the largest in Manitoba’s history. The province responded by developing special assistance programs like the Lake Manitoba Financial Assistance Program, which included assistance for cottage owners for the first time, and several other agriculture assistance programs that were completely provincially funded. While the multi-year flood recovery is ongoing, so far 95 per cent of the program payments under the Lake Manitoba Flood Compensation Program have been paid and over 80 per cent of private disaster financial assistance claims have been closed to date. To date, the total flood expenditure exceeds $1.2 billion.
The next flood outlook is scheduled for the end of March. The detailed forecast with text and charts is available online.
