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Flood risk remains moderate to major in western Manitoba, eases in Red River Valley: provincial government


March 27, 2017   by Canadian Underwriter


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While the risk of overland flooding in Manitoba has been slightly reduced since the provincial government’s outlook in late February, it still remains moderate to major across the province, the provincial infrastructure minister said on Friday.

“‎The province’s Hydrologic Forecast Centre continues to monitor precipitation, spring melt and inflows from the northern United States and the Souris River basin to the west,” Infrastructure Minister Blaine Pedersen said in a press release. “At this time, the Souris River basin continues to be of concern while favourable weather conditions have eased expected flows in the Red River basin. Based on the current outlook, the chance of closing PTH 75 during the spring runoff is low, Pedersen said, referring to Provincial Trunk Highway 75, the main highway from Winnipeg to the Canada-U.S. border.

While levels of spring flooding continue to be dependent on future weather conditions, the potential for spring runoff is “generally normal to above normal” throughout all watersheds, with the exception of the Souris River basin, which has above normal to well-above normal runoff potential. At this time, it is anticipated the province’s major flood infrastructure, including the Red River Floodway and the Portage Diversion, would be activated under unfavourable weather conditions, the release added.

Currently, with unfavourable weather, the outlook suggests the following risk categories:

  • Major risk – watersheds in the southwestern region;
  • Major risk – Eastern region and the Winnipeg River;
  • Moderate to major risk – Pembina River;
  • Moderate to major risk – Roseau River;
  • Moderate to major risk – Assiniboine River;
  • Moderate risk – Interlake region and the Fisher River;
  • Moderate risk – Red River; and
  • Moderate risk – northern Manitoba/The Pas regions and the Saskatchewan, Carrot and Swan rivers.

The forecasted flood levels for major rivers are as follows:

  • The Red River from Emerson to the floodway inlet with normal weather levels would be similar to 2013, with unfavourable weather, observed levels would be similar to 2010;
  • With the benefit of floodway operations, James Avenue 4.6 metres (15 feet) for favourable weather or 5.5m (18 feet) in unfavourable conditions;
  • The Pembina River with normal weather river levels would be similar to 1998, with unfavourable weather levels would be lower than 2011;
  • The Roseau River with normal weather river levels would be similar to 2013, with unfavourable weather levels would be similar to 2011;
  • the Assiniboine River with normal weather river levels from Shellmouth to Brandon would be similar to 2009 but lower than 2005, levels from Brandon to Portage would be similar to 1995 levels, with unfavourable weather levels from Shellmouth to Brandon would be slightly lower than 1976 or 1995, levels from Brandon to Portage would be less than 2011 or the summer of 2014;
  • The Souris River with normal weather river levels at Wawanesa would be similar to 2014 summer levels, with unfavourable weather levels would be lower than 1976 and 2011 levels at Wawanesa; and
  • The Fisher River with normal weather river levels would be similar to 2006, with unfavourable weather levels would be lower than 2008.

Dauphin Lake remains a concern at this time, the report noted, saying that even with normal future weather conditions, the lake could rise above the flood stage. With unfavourable weather conditions between now and the spring runoff, the lake could rise more than 1.5 feet above the flood stage.

Following a municipal tour of potentially affected areas throughout southwestern Manitoba, the minister noted that the province plans and prepares for flood risk predicted with unfavourable weather conditions and the scenario of highest flood risk.

“We want to make sure the lines of communication between our government, local municipalities and emergency officials are open and effective,” said Pedersen. “As we approach the spring melt, our number one concern remains the safety of all communities and Manitobans.”

The province will provide daily flood information to municipalities once runoff commences, which they can use to fine tune flood preparations, the release said.