The province has struggled with accurate predictions in its flood forecasting this year, the kind Manitobans have not witnessed in recent memory, said a University of Manitoba civil engineer.
The overestimate of the Assiniboine River flow, prompting the province to intentially breach one of its dikes and put 150 homes into the line of flooding, is just the latest example, said Jay Doering.
The province is now looking at closing the breach this weekend because the expected flow simply hasn’t materialized.
The province has not said what circumstances led to the error. The province predicted 54,000 to 56,000 cubic feet per second of water would rush down the Assiniboine River. That necessitated cutting the dike because dikes in the lower Assiniboine approaching Winnipeg could not withstand such a flow.
However, the Assiniboine’s flow at Portage has not got up to 52,000 cfs.
The breach in the dike at Highway 331 south of Portage la Prairies was supposed to drain 3,000 cfs, but has carried a mere 400 cfs.
The Portage Diversion is already taking 1,000 cfs less than its high of 34,000 cfs. The 400 cfs through the breached dike could be diverted north, and it would make no difference to Lake Manitoba’s excessive water levels. That should be done immediately, instead of waiting for the weekend, Doering said.
In Brandon, the province issued Flood Bulletin 36 on May 7 forecasting a crest of 33,500 cfs between May 12-14. Instead, the very next day the river hit 35,000 cfs, and flows eventually went to 39,000, Doering said.
"I’m not going to go there," said Doering, when asked whether the province misses the expertise of previous flood forecaster, Alf Warkentin, who piloted the province flood fight for some 40 years. But Doering said that "historically, the province has done a remarkable job both in predicting the timing and the peaks."
He added: "Alf’s flood forecasts, as we know, tended to be very accurate."
Warkentin told the Globe and Mail last week he was surprised the province didn’t call him earier about the problems it was having on the Assiniboine River. The province said it has consulted with him.
Phillip Mutulu had the difficult task of replacing Warkentin this year, in an especially tricky year of flooding.