A Cowichan Valley resident takes a trip through town in his canoe after two local rivers overflowed their banks on Friday. (CBC)

Heavy rain is once again causing Vancouver Island rivers to rise, but emergency officials in the Cowichan region are hoping a temporary dam and low tides will prevent the return of floodwaters.

On the northwest coast of the island, provincial officials issued a flood warning for the Gold River, Heber River, Tahsis and Zeballos areas early Wednesday, after 80 millimetres of rain in 18 hours.

But the threat of flooding eased later Wednesday after heavy rains let up on the northwest coast and allowed brimming rivers to crest and fall.

The rainfall was raising concerns on the southern east coast of the island, after flooding last Friday prompted an evacuation order for 300 homes in the North Cowichan and Duncan areas.

'If the water hits the bottom of the concrete dikes, we would then issue a heightened evacuation alert.' —Emergency Operations spokesperson Joe Barry

Emergency Operations Centre spokesperson Joe Barry said a one-metre-high temporary dam was built on top of the Lakes Road dike.

Barry said emergency crews are monitoring the dam to determine if evacuation alerts or orders are needed

"If the water hits the bottom of the concrete dikes we would then issue a heightened evacuation alert, and if the water were to continue up the concrete dikes we would eventually issue an evacuation order," said Barry.

Low tide at peak flow

The peak rain and river flows are fortunately forecast to come during a period of relatively low tides at the Cowichan River mouth, forecasters are predicting.

The rainfall is expected to peak overnight Wednesday and the Cowichan River is expected to peak by Thursday morning. Tides are expected to be low overnight.

Forty of the 300 homes evacuated last week were so badly water-damaged that they could not be occupied.