Ice jams choked the Red River, backing up water and causing flash floods in communities north of Winnipeg on Wednesday and Thursday. (CBC)

The Canadian military is on standby to help in Manitoba's battle against the impending Red River flood, while authorities told 850 people just north of the U.S. border to be ready to evacuate.

"We're exploring what assistance can be acquired, if needed, through our joint emergency preparedness program," federal Public Safety Minister Peter Van Loan said Thursday in Ottawa.

"And there's, of course, our disaster assistance program, [an] after-the-fact way of assisting with funding, should events arise."

Members of the Canadian Forces came to the province's aid in 1997, lending a hand in sandbagging and building dikes against the rising tide. As they left Winnipeg, they were cheered in a heroes parade down Portage Avenue.

Transportation in Fargo, N.D., has taken new forms as the Red River rises. (CBC)

During that flood, the Red River covered about 2,000 square kilometres — an area equivalent to the size of Prince Edward Island — and caused $4.4 billion in damage between Winnipeg and Grand Forks, N.D. It also forced about 80,000 people from their homes.

MP Vic Toews, president of the Treasury Board and Manitoba's senior cabinet minister, will be in Winnipeg on Friday to meet with provincial officials.

Evacuation alerts for Roseau First Nation, Riverside

Also Thursday, around 850 people from Riverside and the Roseau First Nation reserve, both just north of the U.S. border, were told to be ready to evacuate their homes on short notice.

Don Brennan, acting executive director of Manitoba's Emergency Measures Organization, said evacuation preparations are underway and officials will start moving people out as needed, starting with the elderly and children.

"All the plans are in the offing," Brennan said. "It all depends on the elevation of the water, how fast it's going to approach."

Late Thursday, 95 elders and those with chronic conditions were being taken by chartered buses to Winnipeg from Roseau River as a precaution, said Curtis Smith of the Manitoba Association of Native Fire Fighters.

"The road is eventually going to get washed over, so we want to get the elderly out for that reason," he said.

Terence Nelson, a Roseau First Nation leader, said he had no confidence in the ring dikes surrounding the reserve, noting that they collapsed twice in the flood of 1997.

Record crest

The Red River flows north from the United States into Manitoba before emptying into Lake Winnipeg. The area of current greatest concern along the river valley is Fargo, N.D., where the crest of the flood is expected to hit Saturday.

It is predicted to be somewhere between 12.3 to 12.6 metres — above the devastating 1997 crest of 12 metres — and a record level in the area.

Emergency crews and volunteers in Fargo began building a secondary earthen dike Thursday to back up the primary dike. Officials are concerned the main dike may not be enough to hold back the water.

Early Wednesday, U.S. President Barack Obama declared North Dakota a federal disaster zone, meaning Washington would pick up 75 per cent of state and local government costs to fight the flood.

Peak to hit Winnipeg around April 12

Manitoba senior flood forecaster Alf Warkentin said Thursday the cold weather that has swept across the province is temporarily staving off the flood threat, but ice-clogged culverts, ice jams and the rising Red River will continue to threaten hundreds of homes. The situation will remain tense for at least another three weeks, he said.

"The cold weather could be an ally in this case, drying up the source of water at least temporarily," Warkentin said.

"But there could be a resurgence of this when the snow finally does melt, so it's not over yet. We're going to get another round of overland flooding when this snow melts. What this is doing is prolonging the agony."

Premier Gary Doer, touring areas north of Winnipeg placed on heightened alert, said Thursday the province is trying to break up the ice before it wreaks more damage.

"We're vigilant with overland flooding, we're vigilant on localized flooding with ice jams and we'll continue to be that way until the water goes down right throughout the Red River Valley, and it's obviously going up right now, not down," he said.

The crest is anticipated to hit Winnipeg between April 12 and 17.

With files from the Canadian Press