April 9, 2009 / 9:56 PM / 9 years ago

Canada's Red River may rise higher due to ice

SASKATOON, Saskatchewan (Reuters) - Ice floes on the Red River could threaten flood-fighting efforts in the western Canadian city of Winnipeg and raise the chances of a higher flood crest hitting the region.

A quarter-mile (0.4-km) long sheet of ice has extended from the Red River into the emergency floodway that is designed to protect the city from surging spring floodwaters that are common on the north-flowing Red.

Winnipeg, the provincial capital of Manitoba, may see the river rise to 21.5 feet by Friday, 1.5 feet higher than previously estimated, government officials said on Thursday. Most city properties are protected to 23.5 feet.

The ice started drifting into the floodway on Wednesday, before Manitoba officials took the rare step of raising its gates to prevent widespread flooding caused by ice jams.

The floodway, which diverts excess water into a specially engineered ditch around Winnipeg, naturally allows some water to flow in, but raising the gates increases the flow.

Raising the gates Wednesday saved about 100 homes, said Steve Ashton, the province’s minister of emergency measures. But ice floes have reduced the floodway’s capacity by 30 percent, prompting Manitoba to assemble eight long-reach backhoes, two bulldozers and a crane and ball to try breaking up the floodway ice.

“We are under very unprecedented flows,” said Steve Topping, spokesman for the Manitoba Water Stewardship Department. “It’s almost impossible to predict water levels increasing due to ice jams and where they will occur.”

Officials have measured the ice at 24 to 30 inches thick in places.

They further raised the floodway gates on Thursday to compensate for the waterway’s reduced capacity and to try to keep the river at 20 feet in downtown Winnipeg. The river level was 19.1 feet in the city on Thursday.

The effect of warm, wet weekend weather is the flood fight’s critical factor now. Manitoba officials expect fast melting conditions, combined with rain on Sunday and Monday. The melt may coax ice to move through the city, but it will also thaw snowpack in nearby fields, likely causing some overland flooding, officials said.

Reporting by Rod Nickel; editing by Rob Wilson

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