November 16, 2005

The Lake Winnipeg flood protection system protecting waterfront communities withstood a second significant storm with heavy wave action overnight.

Water levels in the southern portions of the south basins of Lake Winnipeg and Lake Manitoba crested between 4 and 7 a.m. this morning.  Significant wave action was still reported at 11 a.m.  Peak levels for Lake Winnipeg were about half a foot higher than predicted while those on Lake Manitoba were a foot lower than predicted.

·         The peak water levels with wind setup on the west side of Lake Winnipeg for this storm were similar to the Oct. 5 storm.

·         Levels for the south end and east shore of the lake were higher than for the October storm.

·         Newly-constructed dikes successfully held back another storm surge.

·         Manitoba Water Stewardship staff monitored conditions overnight.

·         Dikes did incur some damage and repairs of critical areas are underway.  No dikes were compromised.

The freezing temperatures during the latest storm caused ice build up on trees and buildings due to the spray from wave uprush freezing on contact.  One inch of ice is approximately equivalent to the weight of 10 inches of snow.  Property and building owners should assess the buildup of ice on roofs and how it could affect the structural integrity of their buildings.

Intensity of wave action is site specific and varies by location due to the slope of the shoreline and the exposure to the wind and waves.  Peak levels due to wind setup only have been measured in sheltered areas where wave action is minimal.

Observed peak water levels with wind setup:

Nov. 16           Oct. 5

Lake Winnipeg

Gimli                            717.6 feet         717.5 feet

Victoria Beach              717.4               716.8

Chalet Beach                718.4               718

Lake Manitoba

Westbourne                  813.3               814.7

Estimated peak levels with wave uprush:

Nov. 16           Oct. 5

Lake Winnipeg

Gimli                            720.6               720.5

Victoria Beach              720.4               719.8

Chalet Beach                721.4               721

Lake Manitoba

Westbourne                  816                  817

The occurrence of two such wind and wave events in autumn is extremely rare.  The November storm on Lake Manitoba was significantly less than that of Oct. 5, as winds were not as strong and of shorter duration.  Freeze-up of the lake will depend on weather conditions.

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