Photo: RDKB

Flooding on downtown streets in the City of Grand Forks on May 10.

Officials in the Regional District Kootenay Boundary said more evacuation orders could be given either Wednesday afternoon or Thursday morning.

Chris March, RDKB Emergency Operations Centre director, said the warning is due to "unprecedented fluffing" in the river systems — which he explained is when soil, gravel and other materials fall into rivers due to bank erosion.

"Homes well above the floodplain, in certain locations, are seeing significant bank erosion, and that's making the homes unsafe."

About 1,471 properties remain evacuated in the regional district, affecting about 2,950 people.

The Kettle and Granby rivers both have risen more than 20 centimetres since Tuesday and are expected to rise further, and officials said they are taking an overly-cautious approach to the potential for further flooding in the coming days.

Data from the B.C. River Forecast Centre is somewhat favourable, indicating flows could be well below the record levels seen last week. However, Marsh said that forecast doesn't consider the "worst case" for rain.

He said the flows projected for the Granby River from the province consider if five to 15 millimetres of rain falls, but he said thunderstorms forecasted in the next three days could easily drop 20 to 30 mm in a short timeframe.

"That's what we're faced with, and it's kind of an unknown for us. We're seeking the route of an ounce of prevention and we just want to keep everybody safe."

The City of Grand Forks has formally put in a request for military support to the federal government. 

RDKB chair Roly Russell said it's not an unreasonable request since the closest unit is stationed in Trail, about 90 minutes away.

"We've got a list of operational tasks we can give them as a unit, and they can be self-sufficient... so it would be a resource on the ground that would help us immediately," regional fire chief Dan Derby said.

"They have boats, engineering staff, just manpower that can assist the volunteers who are just exhausted in the community, from seven days of sandbagging in the community."