Floodwaters were receding in southwestern Alberta on Sunday, allowing some residents into their houses to assess damage, but thousands farther east were under orders to leave their homes.

The powerful South Saskatchewan River was rising in Medicine Hat. It was not expected to crest until early Monday morning, but by Sunday morning it was lapping over its banks in low-lying areas and people were busy laying down thousands of sandbags.

A spokesman for the city said a local park and several senior's recreational centres had been cleared out in anticipation of flooding and parts of the city near the river had been closed. Police were patrolling those areas.

Thousands of people were being advised to head for higher ground.

Mayor Norm Boucher said most residents in the city of 10,000 people had obeyed the evacuation order, but a handful were refusing to leave their homes. He warned that officials could not guarantee their safety.

"We're going to go around again to make sure that they're out of there, because the water will be even higher than this and it may be very difficult to reach anybody," said Boucher.

Ron Robinson, the city's director of emergency measures, was asked if people could be forcibly removed from their homes.

Yes, he replied. "They can be fined, they can be jailed. We need to protect lives even if they don't want us to."

Alberta's Premier urged the community to stay strong.

"This is going to be a very challenging time for Medicine Hat," Alison Redford said on a visit there Saturday evening.

"There's going to be a lot of uncertainty and people are going to be afraid. I want people to know we have the opportunity to get through this."

The community of Drumheller -- famous for its dinosaur park -- had also declared a local state of emergency as the Red Deer River rose quickly.

To the west, in Calgary, vacated neighbourhoods along the swollen Bow and Elbow Rivers were showing signs of life again as displaced residents started to trickle home.

Some were returning to properties spared by the flooding, but many were facing extensive repairs to homes and businesses.

Nathan MacBey and his wife found muddy water had risen to about kitchen-counter level in their Calgary home. His basement was swamped and the main floor was covered in wet mud.

"We'd seen flooding and we could keep up to the flooding with our sumps, but this is unprecedented," said the father of two, his voice cracking with emotion.

"Not being able to give our kids a home, that's tough ... We can survive, it's just the instability for the kids."

MacBey left his home early Friday morning after the power went out and water started flowing through the front door.

"It was surge of water. It wasn't lapping, it was a surge," he said as he surveyed the mess the floods had made of his living room.

"Material possessions can be replaced. It's the memories. We don't worry about replacing the desks and the chairs."

Calgary's mayor, Naheed Nenshi, has warned that recovery will be a matter of "weeks and months" and the damage price-tag will be "lots and lots."

And at a briefing Sunday morning, emergency measures chief Bruce Burrell warned that despite the improving situation in Calgary, the city was still in emergency mode.

"We made it to this point with no serious injuries," he added. "Let's keep it that way."

The public got its first look inside the city's Saddledome on Saturday. The home of the NHL's Calgary Flames is flooded up to the eighth row of the lower bowl. Everything below -- seats, boards, dressing rooms, and player equipment -- is a total loss, says the team.

Elsewhere, there is erosion in the Inglewood area of the city and fears that a large chunk of the riverbank along the Bow will be washed away.

PEI's transport minister has called the city offering the expertise of its engineers to ensure that Calgary's bridges are safe.

The mountain town of Canmore was one of the first communities hit when the flooding began on Thursday. Residents have been allowed to return to 260 evacuated homes, but RCMP say 40 more are too damaged to allow people back.

John Marriott lost his backyard when a raging river roared right up to the foundation of his house.

"It's still a lot better than watching it flow away in the creek, which I thought it was going to be," said the wildlife photographer on Saturday afternoon. "I don't want to relocate but I guess you do what you have to do. It's just a house."

The town of High River has been slowly draining, but large areas remained under water Sunday. The lockdown remained in effect and residents had been told it would be days before they were allowed to return.

At least three people have died as a result of the flooding in High River, while a fourth person remains missing.

About 350 members of the Princess Patricia's Canadian Light Infantry from Edmonton have been assisting local RCMP in reaching homes that still haven't been checked. Light Armoured Vehicles have been churning through submerged streets and Zodiac watercraft have been used to reach the hardest-hit areas.

"We have a number of engineers with some boats, some diving capabilities, but really it's a source of labour," said Lieut.-Col. Nick Grimshaw, the Commanding Officer, PPCLI 1st Battalion,.

"We're helping them get into areas that are inaccessible by normal means so we can use our assault boats to do that or our armoured vehicles to move through some of the tighter areas."

Redford was also in High River Saturday and visited an evacuation centre in nearby Nanton.

"I met a little girl at an evacuation girl in Nanton ... named Sienna and she was about five-years-old, and I said to Sienna 'where do you live?' and she said 'I live in High River but I can't go home because my house is filled with water, but someday I'm going to go home,'" the premier recalled.

"I think that's what will stick with me."