Entrance Work Creates A Data Dilemma

Illawarra Mercury

Saturday May 19, 2007

SARAH ALLELY

THE man who predicts the Venice-effect is coming to Lake Illawarra says we need to adapt to the risks of climate change.

Professor Bruce Thom is a member of the Wentworth Group of Concerned Scientists, a former chairman of the Coastal Council of NSW, and has previously worked with the Lake Illawarra Authority.

He said any changes to sea levels would be transferred to the lake.

"If you have a property on the lake, a slab on the ground, you would have already noticed when we get a super high tide," he said.

The lake's tides were very small but the water levels still moved.

Prof Thom said the Venice-effect, a term he coined, was the inundation of low-lying lands caused by more frequent high sea levels: "Leading to water coming up out of the drains and filling the roads and getting into the low-lying back yards, or front yards."

It was more a seeping than a gushing effect.

"When I was in Venice last year I was standing at St Mark's Square, and there was water everywhere."

He said 70 years ago the square in Venice would get flooded 70 times a year. Now it floods 250 times a year.

"That happens a lot in NSW coastal areas, and it happens at Lake Illawarra when you get a strong southerly."

The Venice-effect could become more frequent at the lake.

"It means that the caravans or houses are going to get their feet wet more frequently."

So what do we do to adapt?

"You identify the properties at risk, and the characteristics of these buildings, without frightening people too much."

But the work on the lake entrance threw up a wild card, making it even more difficult to predict water levels.

"We worked hard to get the funds to put in place an entrance that will now stay open more often than it will close."

One option was to build a giant barrier such as with London's Thames River, but Prof Thom doubted these kinds of super structures would be built in NSW.

A dyke along the lake shore and retro-fitted drains were other possibilities. The least popular option was homeowners' compensation.

"It's a topic of considerable importance to people around our coastal lakes, particularly populated coastal lakes like Lake Illawarra," Prom Thom said.

© 2007 Illawarra Mercury

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