The swiftly rising Red River was lapping at the top of sandbag dikes along Scotia Street on Thursday. (Sean Kavanagh/CBC)

As a precaution against rising flood waters, a state of emergency has been declared in certain parts of Winnipeg.

Mayor Sam Katz signed the declaration just before 11:30 a.m. Thursday, while he was helping build sandbag dikes on Scotia Street in the city's West Kildonan neighbourhood.

A Winnipeg man carries belonging from his flooded garage on Glenwood Crescent in the Elmwood neighbourhood on Thursday. (Sean Kavanagh/CBC)

An army of sandbaggers has been working steadily in the area since Tuesday evening, but the river levels have kept pace. As of Thursday morning, they were lapping just 15 centimetres from the top of the dikes.

The level Thursday morning was at 6.72 metres above winter levels. A crest, forecast to be 6.78 metres, is not expected to arrive for a day or two.

On Tuesday, provincial and municipal flood forecasters predicted the crest would be Manitoba's third worst in 100 years. That prompted an appeal by city officials for 500 to 600 volunteers to build sandbag dikes at 100 at-risk properties, including:

• Some on Glenwood Crescent in Elmwood.
• Along the Seine River in St. Boniface.
• Along the Assiniboine River, east of Maryland Avenue.

But by Wednesday, the flood forecast had been revised, with officials announcing the peak flow would exceed the great flood of 1950. Only the flood of 1997, with a crest of 7.47 metres, was worse in the past 100 years.

If not for the floodway diverting water around the city, the 2009 crest would actually be 9.1 metres, officials said.

Following Wednesday's revised forecast, the city increased its plea for volunteers. By late day, it said 800 people had come forward and still more were needed.

Hundreds are out helping again Thursday. They include students from a number of Winnipeg schools who have been given the day off classes.

Katz was among those on the flood front lines, sandbagging when city lawyer Mark O'Neill rushed the emergency document to him to sign.

'It is not a cause for citizens to be anxious; it simply enables our flood-fighting team to respond quickly should localized issues develop.'—Mayor Sam Katz

State-of-emergency status gives municipal officials access to private property to prepare for flooding. For instance, the city is then able to bring in heavy machinery to build earthen dikes.

It also provides officials with the ability to order mandatory evacuations.

"This activation gives us the ability to respond rapidly and decisively to changing conditions," said Katz. "It is not a cause for citizens to be anxious; it simply enables our flood-fighting team to respond quickly should localized issues develop."

The declaration covers all riverside properties along the city's primary dike system, and will remain in effect until April 29.

"So far, our flood-fighting efforts are going well, but this is obviously a major flood event — and we need to be able to act quickly," said Randy Hull, the city's emergency preparedness co-ordinator.

3 distinct flood crests

The crest that will pass through the city this week is not the crest of the flood waters that passed through North Dakota.

'The forecast has been revised upwards, yes, for quite some time now. It's a somewhat unprecedented situation we have here.'—Alf Warkentin, Manitoba's chief flood forecaster

This year is an anomaly in that it will have three distinct flood crests, rather than the usual one. The first crest hit the city last weekend, when the Red River surged over its banks because ice jams impeded its progress.

The current crest was caused by a combination of rain in the past week, along with 18 C temperatures that have caused rapid melting. As a result, many of the rivers in southern Manitoba have become swollen.

Several of those rivers are tributaries that feed into the already-bloated Red River, and the crests of those rivers are all reaching the Red in the next day or two.

"All the worst-case scenarios are coming at us at the same time," said Randy Hull, Winnipeg's emergency measures co-ordinator.

The North Dakota crest waters are expected to reach Winnipeg next week.

They are anticipated to be in Morris, about 70 kilometres south of Winnipeg, on Friday. Already that town is an island in a lake that spreads 16 kilometres wide in places.

Alf Warkentin, Manitoba's chief flood forecaster, said this has been a tough flood to predict.

"The question a lot of people have asked is, 'Why is this getting bigger, sort of every few days, or a day-by-day kind of thing?'" he said. "The forecast has been revised upwards, yes, for quite some time now. It's a somewhat unprecedented situation we have here."