Flood control works saved province from disaster in 2011: report

WINNIPEG — Manitoba’s disastrous flood of 2011 would have been even worse without the sometimes-controversial measures taken to control the water flow, the province says.

Officials released a report Wednesday on 2011 water levels on the Assiniboine River, Lake Manitoba and Lake St. Martin.

The Portage Diversion and other flood-control measures saved several communities along the Assiniboine west of Winnipeg from being flooded, the report says.

It also suggests water levels on Lake Manitoba, which critics have frequently blamed on “artificial flooding,” would have been higher with or without use of the diversion, which diverted water from the swollen Assiniboine at Portage La Prairie up to Lake Manitoba.

The province has pegged the cost of the 2011 flood at about $1 billion, but the report released Wednesday says damage would have been far worse without flood protection measures like the Portage Diversion and Shellmouth Dam in place.

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Image from report released Wednesday showing possible extent of 2011 flooding. Manitoba government

“Emergency flood mitigation measures implemented by the Manitoba government in 2011 prevented an estimated $300 million in damage on the lower Assiniboine River. Under unregulated conditions, without the benefit provided by the Portage Diversion and other flood protection infrastructure, the potential damage on the lower Assiniboine River has been estimated to be $2.2 billion,” the report says.

A summary of the report entitled 2011 Flood:  Technical Review of Lake Manitoba, Lake St. Martin and Assinboine River Water Levels can be found at

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