Media Bulletin - Manitoba

FLOOD BULLETIN #40

Flood Emergency Warning

• There is a significant risk that uncontrolled dike breaches could occur along the Assiniboine River between Portage la Prairie and Winnipeg.  An uncontrolled breach could affect the communities of St. Eustache, Elie, St. François Xavier, Poplar Point, High Bluff, Bernard, Fortier, Starbuck, Sanford and La Salle, as well as the surrounding areas.  An uncontrolled breach would be at an unpredictable location and could contain flows of upwards of 15,000 cubic feet per second (cfs).  An uncontrolled breach of the Assiniboine dikes could potentially affect an area of 500 square kilometres.
• To address high flows and reduce the high possibility of an uncontrolled breach that would affect multiple communities and rural settlement areas, a controlled release of water along the Assiniboine dikes will be undertaken.
• To help prevent the possibility of an uncontrolled breach, a controlled release of 2,000 to 6,000 cfs is necessary.  The release will be through the south side of the Assiniboine dikes and will flood lands within the La Salle watershed adjacent to the Elm River, the Elm River Channel, the Elm River Relief Channel, the Scott Coulee, the Scott Drain and the La Salle River downstream of the Elie dam and reservoir.  This controlled release is necessary to reduce the risk and severity of an uncontrolled breach of the dikes. 
• Fewer than 150 residences will be affected by a controlled release, while 850 homes would be at risk in an uncontrolled breach.
• The controlled release is necessary to reduce the risk and severity of an uncontrolled breach of the dikes and will be initiated as early as Wednesday, May 11.  The controlled release will affect a total area of 225 sq. km in the La Salle watershed east of Portage la Prairie and south of the Canadian National Railway main line in the RMs of Portage la Prairie and Cartier.  The level of the La Salle River in the RM of MacDonald, including the communities of Starbuck, Sanford and La Salle, will also significantly rise. 
• Assistance will be available to help residents who may be affected by flooding caused by this controlled release.
• Overtopping of the east and west dikes of the Portage Diversion Channel in the reach north of the Trans-Canada Highway could occur.  Dikes are being fortified between the diversion gates and the railway bridge located 1.6 km north of the Trans-Canada Highway.  Crews are also working on the embankments to increase the channel capacity to 31,000 cfs from 25,000 cfs.
• Residents in the at-risk areas in the RMs of Portage la Prairie, Cartier, St. François Xavier and Headingley are on an evacuation notice and should prepare their final evacuation plans.  The city of Portage la Prairie is not included in this evacuation notice at this time.
• Residents in the area expected to be flooded by overtopping of the Portage Diversion dikes have been put on evacuation alert and are to remain vigilant.

Assiniboine River Flood Response Plan

• Unstable weather bringing significant rain to most of southern Manitoba and increasing flows on the Assiniboine River are presenting significant issues.
• The Assiniboine River dikes between Portage la Prairie and Baie St. Paul will be vulnerable to high flows for the next two weeks.  Due to this vulnerability, uncontrolled breaches along Assiniboine River dikes may occur in the RMs of Portage la Prairie, Cartier, and St. Francois Xavier and may require evacuation.
• The flows coming into the Portage reservoir are very high.  After reviewing five flood-risk scenarios, the current flood-management plan was selected as it will impact the least number of homes, cottages, businesses, infrastructure and agricultural lands.
• Flows in the Portage Diversion will be increased to above design capacity to provide as much possible protection on the river downstream of Portage la Prairie.  Overtopping is expected on the east and west side of the Portage Diversion dikes north of Portage la Prairie.  Dikes are being fortified adjacent to Portage la Prairie to prevent flood waters from affecting the city. 
• Downstream of the diversion on the Assiniboine River, a controlled release is planned near the Hoop and Holler Bend (between Southport and Newton) which will flood lands within the La Salle River Watershed in the following areas:
  • Elm River,
  • Elm River relief channel,
  • Scott Coulee,
  • Scott Drain, and
  • the La Salle River downstream of the Elie dam and reservoir. 
• It is anticipated the above areas will be affected with floodwaters and residents are advised to make preparations for evacuation. 
• Controlled releases prevent potentially more catastrophic breaches of dikes that would result in significant flooding of much larger populated areas.
• Based on rainfall projections, it is anticipated that flows at the Portage reservoir will reach:
  • 43,000 cfs on May 9,
  • 47,000 cfs on May 10, and
  • 51,000 cfs on May 11.