Seven families were forced to leave their homes near Port Alberni on Vancouver Island Sunday after the rain-swelled Somass River threatened to flood.

The families, from the Tseshaht Nation, all live along the river, which is rising again from heavy rain that started afresh Sunday morning.

The evacuation marks the third time this month that families have been forced to flee due to flooding threats caused by rain.

"They're getting a bit of flood fatigue here," said Hugh Braker, the Tseshaht Nation's emergency planning coordinator.

Braker said crews erected sandbags around affected homes on Saturday.

The reserve has another few thousand sandbags filled and on standby if the region does flood again, which is expected, he added.

Environment Canada said up to 80 millimetres of rain is expected to fall on the west and north parts of Vancouver Island Sunday evening.

No opportunity for rivers, lakes to drain 

"The flooding is really expected to ramp up this evening," Braker said.

Emergency crews are also bracing for floods along Highway 4, which crosses the island, connecting Parksville to Ucluelet.

​One lane of that road has already been closed due to a landslide early Sunday morning, Braker said.

He said the amount of rain that's fallen in the region is significant, even by West Coast standards.

"We have had floods before, but this is unusual because it is so protracted," Braker said.

"The problem is the rivers and the lakes do not have an opportunity to drain."

He said families from evacuated homes are to be taken to a hotel in Port Alberni for at least two days.