The rising waters of B.C.'s mighty Fraser River are threatening low-lying homes in Prince George and Chilliwack, triggering evacuation orders and alerts in the two communities.

On Monday the City of Prince George declared a local state of emergency and issued an evacuation order to 18 homes. By Tuesday morning, the water was surrounding some at houses on Farrell Street and flowing quickly through Paddlewheel Park by the riverside.

The houses and trailers between the dike and river aren't protected, and as of Tuesday morning water was lapping up around the edges of some and almost completely surrounding others.

Neil Hamilton, the engineer in charge of the dike, said the riverbank was not safe enough to build on to protect those residents.

Farrell St., Prince George

"If you try to build back here ... you're going to sink. Put any weight on it, and it sinks right into the ground," he said.

"So as soon as you try to build anything back here, you cause destabilization of the bank, the ability for somebody to fall into the river in the night — it's just not worth risking people's lives to put stuff back here."

Hamilton says the dike is built to up to 10.8 meters at the lowest point.

City officials pumping water over a temporary gabion dike in the neighbourhood said the river was at 9.8 metres on Tuesday morning.

David Campbell of the River Forecast Centre says the flood waters are expected to peak on Tuesday evening in Prince George at the highest levels recorded in decades.

"The current forecast of peak level for South Fort George is 10.3 to 10.8 metres. This is approximately a 50-year flow for this station. For comparison floods in 2007 reached 9.84 metres and in 1972 — the last large flood — levels reached 10.4 metres."

Flow to peak Friday in Chilliwack

Campbell says the surge of water will continue through the Fraser Canyon on Wednesday and Thursday and the peak flow will reach the Fraser Valley around Chilliwack by Friday.

Chilliwack, B.C.

An evacuation alert was issued Monday for dozens of Fraser Valley homes outside Chilliwack's diking system. City spokesperson Starlee Renton says people living outside the dikes have been told they may have to leave quickly.

"There are about 200 properties in total outside the system and there are 42 homes, and this evacuation alert means residents in this area should be prepared to leave on short notice."

Emergency officials in Port Coquitlam and New Westminster are also keeping a close eye on low-lying riverside areas.

Campbell warns with more rain in the long-term forecast and plenty of snow still in the mountains, the river could surge again next week.

"We haven't a lot of time to recover, so the rivers are going to remain fairly full and then have to deal with whatever weather we do get. So you know, certainly it sounds like at least another pulse coming in."

Other warnings and advisories

As of Tuesday morning, B.C. River Forecast Centre flood warnings remained in effect for the Fraser River at Prince George and upstream, and downstream from Quesnel to Fraser Canyon. A high streamflow advisory remains in place for the Lower Fraser River.

On Tuesday afternoon, the forecast centre issued a flood advisory for the North and South Thompson rivers, warning that water levels on both rivers will likely rise at least 60 centimeters over the next few days.

It also warned that as of Wednesday all boat launches will be closed, and the City of Kamloops is asking boaters to stay off the water.

The B.C. River Forecast Centre updated its other flood watches, warnings and advisories at 9 a.m. PT.

• Shuswap River downstream of Mabel Lake (near Enderby) — flood warning.
• Shuswap River upstream of Mabel Lake (near Lumby) — flood watch.
• North Thompson River and tributaries — flood advisory.
• South Thompson River and Shuswap Lake — flood advisory.
• Quesnel River — flood watch.
• Nechako River near Prince George — high streamflow advisory.
• North Thompson River and tributaries — high streamflow advisory (downgraded).
• Cariboo region (including the Horsefly River) — high streamflow advisory (downgraded).
• Skeena and tributaries (including Bulkley River) — ended.
• Upper Columbia River and tributaries — ended.
• Seymour River and Eagle River (Shuswap tributaries) — ended.
• Okanagan (including North Okanagan and Mission Creek) — ended.

DriveBC is reporting river ferries at Big Bar, Little Fort, Lytton, McLure and Usk have all been closed because of high water.

With files from the Canadian Press.