The alliance covers seven councils in the south-east including Mornington Peninsula Shire.

Its award-winning report published last year, Impacts of Climate Change on Human Settlements in the Western Port Region: an Integrated Assessment, included worrying data about the threat of rising seas and more storms affecting municipalities on Port Phillip.

Water worries are set against the backdrop of the State Government warning planners they should factor in an 80-centimetre sea level rise over the next 100 years for projects near the coast.

Three recent planning decision show councils are worried about rising seas:

Casey Council has forced a home owner to install three-metre high stumps under a planned house at Warneet on the northern coast of Western Port.

Wellington Shire backed down on a ban on building homes at The Honeysuckles near Ninety Mile Beach in Gippsland, but wants home owners in low-lying coastal areas to be slugged with extra building conditions or forced to indemnify the council of any responsibility in the event of flood.

Gippsland Coastal Board stopped the building of houses at Toora on Corner Inlet overlooking Wilsons Promontory after South Gippsland Shire approved them. This was the first case in Australia where climate change has been given as a reason to refuse a coastal development.

Port Phillip channel deepening monitor Mick Bourke said late last month the bay's high tides had risen just one centimetre since dredging at The Heads ended.

Six months of tidal height data scrutinised by the Office of the Environmental Monitor showed the increase was consistent with predictions.

"The project's environmental assessment process predicted that after the entrance to the bay was deepened, tides within Port Phillip would increase around one centimetre," he said.

"Dredging at the entrance ended in September 2008, and the evidence from tidal height monitoring to date shows us that tidal height changes in the order of one centimetre are beginning to be detected within the bay.

"High tides have risen up to one centimetre and low tides have decreased by a similar amount."

Mr Bourke said a full year of around-the-clock tide and sea level monitoring would continue up to the end of September.

However, anti-dredging campaigner Jenny Warfe, president of Blue Wedges Coalition, quotes the controversial Bruun Rule.

"It states that for every one unit that water rises vertically it can spread up to 100 units horizontally on low-lying land," she said.

"The imperceptible 1centimetre that the PoMC and OEM talk about can mean up to 1metre of previously dry land being inundated.

"There's a lot of very important and valuable infrastructure in this zone, including in my area the main trunk sewer from Dromana to Rosebud that runs along the northern side of Point Nepean Road from Dromana. It crosses back on to the landward side of the road right where rocks are collapsing and the cliff below is eroding.

"The extra water moving in and out of Port Phillip on every tide change, as a result of dredging, was calculated in the 2004 EES to be 20million cubic metres. This may not seem to be much when spread out over the entire bay, but the extra volume and weight of water must contribute to erosion, especially during storm surges, low pressure and 'high' high tides."