The ground along the riverbank is heaving in some areas as the slope shifts. (CBC)

Residents of eight homes along Saskatoon's riverbank are staying put so far, after being asked to voluntarily evacuate because of shifting in the slope along the river.

The families were asked to leave their homes along 11th Street East Friday by the city, which called the slope movement a growing danger. It said monitoring this week revealed a serious increase in the rate of movement of the earth.

The city said the riverbank slope is shifting a few centimetres each day on average, but moved at least 20 centimetres one day last week.

"The new east slope has moved about a metre horizontally," said strategic services manager Rob Frank on Saturday.

"The depth of that slope's failure is approximately nine metres deep. So we're talking about a massive amount of soil moving. It's not moving at an extremely fast rate but it has increased its speed."

Saskatoon Fire Chief Dan Paulsen warned residents to be prepared for complete failure of the slope.

"You think about whether you live on a fault line or a tsunami line, everybody has natural events that are happening and this just happens to be one in Saskatoon that we're faced with."

Paulsen said the city will consider mandatory evacuations if the concern about public safety grows.

Officials plan to meet with residents for an update on Tuesday.

Some residents CBC spoke with on Friday said they were waiting for more information before they made their decision.