Residents are fighting a losing battle with sandbags and sump pumps as floodwaters surge in Port Alberni and the Cowichan Valley.

Homeowners along Sproat Lake have been watching in fear as their properties are submerged by rapidly rising water levels.

"You're seeing it flooding about 10 feet up from where it normally is," said homeowner Terri St. Jacques, motioning to the rapidly encroaching water line. "This walkway normally, in the summer, is on the ground."

St. Jacques said the flooding is concerning after two similar floods in the last three years – and it has her questioning whether the problem is man-made.

Should weir be lifted?

Catalyst Paper owns a weir at the mouth of Sproat Lake that has three removable plates which hold back roughly 3.6-million litres of water a day, and a sweep that stops debris from flowing down river.

St. Jacques and other homeowners say they're concerned that the company isn't doing enough to address the high water levels.

"Our frustration and mine in particular is who is responsible for the stewardship of the lake, and what is going on with this flooding?" she said.

Port Alberni's mayor says while the weir plates used to be lifted every fall, they haven't been for more than a decade – and fears it's posing a threat to the city.

"My concern is that if the high water isn't addressed, not only do we have an issue here with flooding, but we have a potential issue downstream," said Mike Ruttan. "If the weir should break down or the sweep should be broken, then all of this stuff could head downstream in a fairly significant pulse."

Ruttan says Catalyst agreed to lower a plate earlier this month, but due to high water levels and pressure it might not be safe to lift any more plates.

"That's the question is when will it be safe to do so?" said Ruttan. "It's the force of the water that keeps the debris there, and the higher the lake rises, the greater the force."

With 75 millimetres of rain forecast to fall in the Alberni Valley this weekend, homeowners say they're preparing for the possibility of yet another flood.

In a statement Catalyst says it’s been working with the Regional District and local stakeholders to address what is a complex issue.

“Several weeks ago, at the direction of the Regional District, Catalyst removed one of the three steel plates on the weir to increase water flow and reduce the potential for flooding,” said Director of Communications Eduarda Hodgins. “We will continue to work proactively with the Regional District as one of many stakeholders involved in addressing this issue.”

Lake Cowichan breaches its banks

Further south, in Lake Cowichan, water spilled over banks and began taking over parks, roads and moved up on some homes Friday.

A CTV viewer shared pictures of a home near the Cowichan River that was overtaken by floodwater, one of many affected by the rising water levels.

"The river has come up significantly over the last couple of days. I guess probably five or six feet," said Jackie Root, who lives on Prospect Ave. "Every couple of hours you can see that the water has risen even more."

The BC River Forecast Centre had already issued a high streamflow advisory for the Cowichan River, and more heavy rainfall is expected this weekend on Vancouver Island, particularly for the western and inland island.

High streamflow advisories have also been issued for the Somass, Sproat and Stamp rivers and their tributaries.

With a report from CTV Vancouver Island's Jessica Lepp