rising tides in port phillip bay – is channel deepening to blame?

Sue Pennicuik MLC

State Member of Parliament for Southern Metropolitan Region

"There have been growing reports of higher tides, beach erosion, faster currents and an increase in swell (surge from Bass Strait) since the Entrance to Port Phillip Bay was deepened," Greens MP, Sue Pennicuik said today.

The Office of Environmental Monitor (OEM) is reported1 as saying that there is no evidence to suggest that dredging is to blame for erosion at Portsea beach; and that the most likely explanation was natural erosion caused by the local impact of storms and seasonally high tides, exacerbated by the swell rolling in from Bass Strait.

"Tidal data that I have obtained from the Port of Melbourne Corporation and have had analysed, supports what so many residents, swimmers, divers and other businesses in the southern part of part Phillip Bay have been reporting since channel deepening: that tides are higher in the south of the Bay" said Greens MP, Sue Pennicuik today.

"Preliminary analysis of wind data from the past ten years suggests that wind beach erosion, particularly at Portsea was not caused by seasonal weather events alone," she said.

"I am very worried about the tidal changes that are being seen at many places round the south of Port Phillip Bay," said Ms Pennicuik. "It is one of the most serious effects of the channel deepening project that the government was clearly warned about at the time."

"The preliminary analysis that I am releasing today strongly suggests that the average daily high tides have increased significantly at four points in the south of the Bay, by much more than was predicted by the Port of Melbourne on the basis of 'expert advice' in the Channel Deepening Project (CDP) Supplementary Environmental Effects Study2. However, more data is needed about tides, swells, currents and weather events to be able to know for certain what is happening in the south of the Bay", Ms Pennicuik said.

"Unfortunately, the five metres of sea bed and rock can't be put back at the Entrance and Port Phillip Bay may be permanently damaged as a result of the expensive channel deepening project that we didn't need," she said.