A series of rainstorms has swollen the Somass River near Port Alberni to near-historic levels and the water could go higher on Wednesday, the B.C. River Forecast Centre said.

A flood watch for the Sproat and Somass Rivers was upgraded to a flood warning late Tuesday, which means rivers are about to or have already started overflowing their banks.

"We would expect flooding, or high flow conditions, to persist through Thursday, at least," said Tobi Gardner, a hydrologist with the B.C. River Forecast Centre.

No serious flooding is expected in the City of Port Alberni. But flood waters from the swollen Somass River started to surround homes in the Tseshaht First Nation on Tuesday.

The community said 14 houses in a low-lying area of the reserve are at risk for flood damage and families are being evacuated from those homes as needed.

"It's very stressful for people to [have to] evacuate. They are not at their home. They get worried about what is happening to it, so we have a lot of stress in the community," said Tseshaht emergency coordinator Hugh Braker.

The rising water has also closed Highway 4 to Ucluelet and Tofino.

The Ministry of Transportation said detours are in place using side roads, but there could be delays because a pilot vehicle is required to lead traffic through.

The rain is expected to ease up on Wednesday and Thursday, but some of the precipitation that has already fallen is still making its way down from the mountains around Port Alberni, Gardner added.

"The system is still moving through all this massive volume of rain," he said.

Another storm is heading for B.C.'s south coast on Friday, Gardner added.

Campbell River on flood watch

​Record rainfall has hit the watersheds on the northern half of Vancouver Island over the past couple of weeks.

The deluge has creating conditions BC Hydro has not dealt with in the Campbell River area since the 1950s, said spokesperson Stephen Watson.

"We are seeing more water in a one and a two week period that we have ever seen before and that just speaks to the continuous storm activity," he said.

The utility has been forced to spill more water from reservoirs. Nearly a hundred homes and businesses could experience flooding if the Campbell River rises over its banks. 

"Right now there has been no breach, but we are trying to be as reactive as we can," said Mayor Andy Adams. 

The City of Campbell River is providing sandbags to help people in low-lying areas prevent flood damage. They are available at the city's Dogwood Operations Centre at 385 S. Dogwood or the Emcon yard at 7025 Gold River Highway.