March 18, 2010
Manitoba Spring Flood Outlook Improves As a Result of Recent Weather
– – –Significant Flooding in Red River Valley Still Expected
Manitoba Water Stewardship’s Hydrologic Forecast Centre has evaluated conditions in the province and an updated spring flood outlook indicates that mild weather is resulting in a slow, steady melt about two weeks earlier than normal. The Red River is predicted to peak in Winnipeg in early April.
Flooding is expected along the Red River at the 2006 level, about 0.9 metres (three feet) below the levels of 2009. The weather from this point forward is still an important factor and could affect the flood outlook.
The 2010 spring run-off is expected to be average or below average in most parts of Manitoba, except for some areas near the U.S. boundary where above-average run-off is expected. As well, flooding is expected along portions of the Souris and Pembina rivers from late March to early April.
Crests on the Red River in the Manitoba portion are expected to be similar to 2006, the sixth largest in the past 100 years and a little lower than 1979 and 1996. There is still a small possibility of a flood of 2009 proportions, but it would be caused by adverse weather such as a heavy snowstorm or a significant rainstorm.
Run-off on the Red River is quite advanced with the crest expected in the Fargo and Grand Forks areas this weekend. Crests in Manitoba are expected in late March or early April.
The new flood outlook for Manitoba is based on all available information including recent forecasts for locations south of the international border issued by the U.S. National Weather Service.
· The dry weather of the past five weeks and early run-off in Manitoba is reducing projected Red River crests. Most eastern tributaries of the Red River from northern Minnesota to Winnipeg have already crested and will not be contributing much flow when the Red River crest arrives in Manitoba. Some uncertainty remains with respect to the effect of western tributaries from northern North Dakota to the Morris area, which have just started to run.
· Operation of flood control works is expected to keep the crest in Winnipeg below 5.9 m (19.5 ft.) at James Avenue. The 2009 crest was 6.8 m (22.5 ft.) and the 1997 crest was 7.5 m (24.5 ft.). Operation of the Red River Floodway could begin as early as March 24.
· Flooding is unlikely in the area from Selkirk to Breezy Point this spring, although the possibility cannot be ruled out. Ice monitoring shows the ice is of normal thickness and is relatively weak. Extensive ice-cutting and breaking is helping to reduce the potential for ice jams.
· The spring run-off is underway in southern Manitoba and is about two weeks earlier than average. Run-off is well advanced in the Red River watershed with crests on the Red River expected near the end of March or in early April. Run-off is just getting underway in the Assiniboine, Pembina and Souris river watersheds, where sub-freezing temperatures during the next five days will slow the melt and run-off process.
· There had been very little flooding as of mid-March. Flooding is expected to develop along the Red River next week and along portions of the Souris and Pembina rivers from late March to early April. Little or no flooding is expected along most smaller streams in Manitoba due to minimal precipitation from mid-February to mid-March and a gradual melt. The spring flood potential could still change if heavy snow or rain were to develop from now until mid-April.
· Sub-freezing temperatures during the next five days could cause ice to form on some fields and could cause minor icing on smaller streams. However, it is very unlikely the severe icing problems experienced last year will be repeated, as temperatures will not be as low as last spring and there is less water on fields this spring.
Watershed Conditions
Snow surveying was done in the Pembina River watershed, the Interlake and in western Manitoba March 8 to 10. These surveys indicated little change in snow water content since mid-February.
River Forecasts
Predicted peak stages include backwater effects from stationary icebut do not include effects of possible ice jams. Brief flooding can occur in locations where ice jams develop, even with
below-average river flows.
below-average river flows.
Red River Mainstem
Run-off is quite advanced, with the crest expected in the Fargo and Grand Forks areas this weekend.
· Crests in Manitoba are expected in late March or early April.
· Crests in Manitoba are expected to be similar to those of 2006, the sixth largest in the past
100 years and a little lower than 1979 and 1996.
100 years and a little lower than 1979 and 1996.
· Ring-dike closures at communities in the Red River Valley will be made as required, with a minimum disruption to transportation.
Red River Tributaries
· Eastern tributaries have already crested except for the Roseau River, which is not expected to flood.
· Minor flooding could occur in the Buffalo River, Deadhorse Creek, Shannon Creek and Aux Marais watersheds this weekend. Flooding is not expected on other western streams.
Pembina River
The flood potential is moderate on the Pembina River and, with soil moisture significantly lower than last year, much of the water is expected to soak into the ground. However, the following conditions are anticipated:
· flooding is expected between Rock and Swan lakes;
· minor overland flooding is expected in many areas, but much less than last spring; and
· levels of Rock Lake should be 0.6 to 0.9 m (two to three ft.) lower than 2009.
Assiniboine River Mainstem
· Near bank-full conditions are expected from St. Lazare to Brandon, based on favourable weather from now on, with minor overbank conditions possible in the lowest areas.
· Shellmouth Reservoir outflows have been reduced to 200 cubic feet per second in order to further reduce peak levels along the Assiniboine River.
· The Portage Diversion will be operated, if required, to prevent ice jams and flooding from Portage la Prairie to Winnipeg.
Assiniboine River Tributaries
· Flooding is unlikely along Assiniboine River tributaries, due to a gradual melt.
Souris River
· Flooding of agricultural lands from the U.S. boundary to near Melita is expected but peak water levels should be significantly lower than last year and only slightly higher than those of 2005, based on normal weather from now on. Buildings will not be affected.
Souris River Tributaries
· Some flooding could occur along Pipestone Creek unless the melt remains very slow.
Interlake Region
· Run-off is well underway on the Fisher River. Levels at Peguis First Nation are well below flood stage. Flooding is not anticipated.
· Flooding is not expected on the Icelandic River unless serious ice jams develop.
· Minor overland flooding of low-lying areas is expected, based on normal weather from now on.
Eastern Region
· Run-off is well advanced and flooding is minimal. Adverse weather could still cause a problem but this is unlikely due to rivers being near the crest and the cool, dry weather predicted.
Westman and The Pas Regions
· Minor flooding of low-lying areas is possible. No significant flooding is expected unless adverse weather develops.
Northern Manitoba
Run-off in most of northern Manitoba (north of latitude 54) is expected to be below average and flooding is unlikely.
This will be the last spring flood outlook, unless unusual weather conditions develop. River forecasts with current and predicted peak stages will be issued daily for the duration of flooding.
The latest information on flood forecasts for Manitoba is available at:
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