People living in some flood-threatened Ottawa neighbourhoods could be asked to leave their homes in the coming days as water levels on the Ottawa River continue to rise.

The city ward most at risk is West Carleton-March, which includes the neighbourhood of Constance Bay, deputy mayor George Darouze said at a news conference Friday afternoon.

People living in the Cumberland and Britannia neighbourhoods could also be asked to flee if conditions deteriorate, Darouze said.

Darouze's comments came after members of the Canadian Armed Forces arrived in Ottawa this morning to deal with flooding as water levels along the Ottawa River continue to rise and a rainfall warning threatens to make things even worse.

This year's flooding could exceed 2017's levels by 40 to 50 centimetres in some areas by the middle of next week, officials have said.

If that were to happen, it would present "a number of risks," city manager Steve Kanellakos said at Friday's news conference.

I don't want to mince words. If we call for voluntary evacuations, there could be real repercussions if residents choose to ignore that advice. - City manager Steve Kanellakos

Streets could flood or even be completely washed out, making it nearly impossible for emergency vehicles to get to stranded residents, Kanellakos said.

If homes are flooded, hydro and gas would also be shut off — which could pose additional dangers with near-freezing temperatures expected Saturday, he added.

Watch as Ottawa's city manager said residents should be ready to leave their homes:

Steve Kanellakos says some residents may be in danger if they ignore a voluntary evacuation order. 1:09

"The city cannot compel people to leave their homes. That said, I don't want to mince words," Kanellakos warned. "If we call for voluntary evacuations, there could be real repercussions if residents choose to ignore that advice and remain in place."

Emergency teams are currently visiting people living in threatened areas to inform them of the risk, he said. Teams will also go door-to-door identifying residents with accessibility issues or medical needs that could make evacuations more difficult, he added.

Both Kanellakos and Darouze said residents willingly left their homes behind when there was a similar request during the 2017 floods.

About 400 troops are being deployed in key areas of Ottawa, including Constance Bay, as a state of emergency continues. (Krystalle Ramlakhan/CBC)

Military arrived Friday morning

The military arrived in the rural northwest Ottawa community of Constance Bay just before 9 a.m. ET, where residents and volunteers have been filling up sandbags for days.

About 400 troops are expected to be deployed to key areas to help with sandbagging and other efforts.

The troops arrived after Ottawa Mayor Jim Watson declared a state of emergency Thursday, not long after Environment Canada issued a forecast predicting that up to 35 millimetres of rain could fall by Saturday morning.

By Friday morning, Environment Canada had upgraded the special weather statement to a rainfall warning "due to the limited ability of the ground to absorb this rainfall," the agency said in a notice posted on its website.

Pierre Poirier, the City of Ottawa's manager of security and emergency management, said Friday afternoon water levels on the river at Lac Deschênes, west of downtown and just downstream from Constance Bay, had risen 20 centimetres since the morning.

People in Constance Bay are filling up sand bags to take to their homes to help protect them from flooding. There is also a call for volunteers to help fill sand bags. This is the third disaster the community is facing in two years. Flooding 2017 and tornado 2018. <a href="https://twitter.com/hashtag/ottnews?src=hash&ref_src=twsrc%5Etfw">#ottnews</a> <a href="https://t.co/ihT7IgViux">pic.twitter.com/ihT7IgViux</a> —@Krystalle_CBC

Premier tours area

While touring the Constance Bay area Friday morning, Ontario Premier Doug Ford said he believes climate change is among the reasons eastern Ontario homeowners are trying to save their homes from flooding for the second time in three years.

Ford said that when you see the affected people face-to-face, it "just rips your heart out," and added they can't be expected to go through this every year.

Ontario Premier Doug Ford came to Ottawa Friday morning to meet with officials and tour flooded areas. (Jonathan DuPaul/CBC)

He said he's willing to sit down with the communities to talk about what is needed to protect their homes or offer compensation to move to higher ground, things both Quebec Premier François Legault and New Brunswick Premier Blaine Higgs are looking at as they also deal with flooding in their provinces.

The Ontario government asked for federal help Thursday, and Public Safety Minister Ralph Goodale said that will come.

Premier Doug Ford says help from the Canadian Armed Forces gives residents a sense of security. 0:25

Ralph Goodale says the flooding in the National Capital Region is being made worse by steady rainfall and continuous snow melt. 1:19

On the Quebec side of the river

In Gatineau, Que., across the river from Ottawa, the navy has been helping with evacuations by boat.

"Exceptional" flood levels are expected to be reached first in the city's Aylmer and Pointe-Gatineau neighbourhoods.

About 713 flood victims from 342 homes had registered with the city as of Friday morning, many of them from the Boulevard Hurtubise area near Lac Beauchamp.

Further east, in the western Laurentians, a bursting Rouge River and possible failure of the Bell Falls Dam led to a mandatory evacuation order Thursday.

The 104-year-old dam was built to withstand flows of up to about 980 cubic metres per second, which is what it is currently seeing. But Hydro-Québec officials believe the flow could increase to 1,300 cubic metres per second.

They expect the dam to hold even at that higher flow rate, but are evacuating the area as a precaution.