Continued unfavourable weather could result in levels higher Than 2009
Manitoba Infrastructure and Transportation’s Hydrologic Forecast Centre issued an update today regarding additional snow in the Red River Valley, which reports:
The flood risk on the Red River south of Winnipeg is slightly higher than predicted in the province’s March flood outlook and is approaching the unfavourable weather scenario, which could result in major flooding in the Red River Valley. The outlook indicates river levels could be half a foot to one ft higher than in 2009, which is significantly less than 1997 levels, from Emerson to Winnipeg. The increased flood risk is a result of significant snow fall in the Red River Valley including recent storms in North Dakota that resulted in more precipitation than is normally seen in the entire month of April.
Unseasonably cold weather has continued to delay the spring meltA rapid spring melt and the potential for spring rainstorms could aggravate overland flooding and increase flows on tributaries.
Based on the Environment Canada long-range weather forecast, melt and subsequent run-off could start as early as this weekend, though it would require sustained warmer conditions with temperatures above freezing overnight.
The U.SNational Weather Service predicts the Red River will not crest in the United States until mid-May, meaning the crest could arrive in Winnipeg as late as the last week of May. In 2009 there was an early melt with the Red River cresting in Winnipeg April 16The latest major spring flood crest for Winnipeg was May 19, 1950.
Red River
Favourable weather would result in minor localized flooding, median conditions could produce minor to moderate flooding similar to 2011 and unfavourable weather conditions could result in major flooding, 0.5 ft to one ft higher than in 2009, which is significantly less than 1997 levels, from Emerson to Winnipeg. The outlook indicated conditions are trending towards the unfavourable weather scenario.
The flood potential on the Red River is trending to the unfavourable weather scenario due to recent snow storms, which contributed substantially to the U.SsnowpackSome locations saw a record snowfall for one day.
Under these conditions, the forecast indicates partial closures will be required for all 18 Red River Valley community ring dikes.
The forecast indicates PTH 75 will be closed. A PTH 75 detour was in place for 36 days in 2009 and 44 days in 1997.
The government of Manitoba has equipment and material ready to respond to the need for dike closures.
The forecast indicates evacuations for rural homes and farms are expected. In 2009, about 250 homes and farms in the Red River Valley were evacuated.
Levels at James Avenue are forecast to be 17.7 ft James* under favourable conditions, 18.8 ft James* for average conditions and 21.5 ft James* for unfavourable weather conditions. The 2009 peak was 22.5 ft James*
Water levels on the Red River north of the city of Winnipeg are likely to be close to those of 2009A major issue that year was 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 the North Red River Buyout Program.
A permanent dike has been constructed around the Kiwanis Seniors Centre in Selkirk, and a dike constructed in 2011 remains in place at Peltz Drive in St. Clements.
Manitoba’s Amphibex fleet broke 29 kilometres of ice on the Red River north of Winnipeg, with double-wide swaths, the most surface area of ice ever crushed in the province. Since then, the Amphibex fleet has also worked on the Portage Diversion and the Assiniboine, Whitemud, Fisher, Icelandic and Brokenhead rivers and can be deployed quickly to trouble spots throughout the province to break up ice jams as needed.
Assiniboine River
The province has stationed a sandbag machine in Brandon and has started installing a super-sandbag dike along 18th Street. The city of Brandon linear dikes provide protection to a one-in-300 year flood, as was seen in 2011Even with an unfavourable weather scenario, flood levels are not expected to approach 2011 levels.
East of Portage la Prairie, provincial crews have inspected and reinforced critical sections of the lower Assiniboine River dikes, which were heavily damaged in the 2011 flood. Heavy earth-moving machinery will be ready on mobile trailers if needed for additional dike support during a flood.
Under all weather scenarios, the diversion will be required to manage ice jamming on the Assiniboine River east of Portage la Prairie and to provide flood protection to the city of Winnipeg. The flow range is expected to be between 9,400 cubic feet per second (cfs) and 19,500 cfs depending on weather conditions. The diversion is not in operation at this time.
Duration of diversion flows will be much shorter than in 2011, unless heavy spring and summer rainfall develops, and is not expected to have a significant impact on Lake Manitoba levels. Lake Manitoba is currently at 811.8 ft above sea level (asl). With average weather, the lake is expected to peak at 812.4 ft., close to its top operating range of 812.5 ft., but could peak at 813.3 ft with unfavourable conditionsGeo-tube wave breakers are in place at locations at Delta Beach, Twin Lakes Beach and in the RM of St. Laurent at Sandpiper Beach.
The province has also stationed earth-moving equipment at the outlet of the emergency channel as a contingency should it be required in the event of extreme water levels on Lake Manitoba and Lake St. Martin. The channel successfully brought Lake Manitoba and Lake St. Martin into operating range in 2012.
The conditions for the Souris, Roseau and Pembina rivers have not changed from the flood outlook issued on April 10.
Flood-fighting equipment has been placed around the province to bolster emergency response. This includes two million sandbags, six sandbagging machines, 17,000 super sandbags, 43 kilometres of Hesco cage barriers, 50 km of water-filled barriers, and 34 mobile pumps ready to deploy on an emergency basis provincewide.
* James refers to the long-term mean winter ice level at James Avenue in Winnipeg
