About $4 million needs to be spent immediately to fix the current problems but the total cost of improving the system could be more than $20 million, city infrastructure manager Geoff Brayford said.
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At last week's Council meeting, alderman unanimously agreed that the 40 to 50-year-old concrete retaining walls, earth levees and mud-box structures protecting the city were their No.1 priority.
The levees have been a contentious issue since they were constructed in the late 1960s, many experts claiming they were not adequate from the outset.
But had they not been built, the Invermay of today would never have been possible.
"Every day twice a day (at high tide) 40 per cent of Invermay would be under water if we didn't have the levee banks, cut-off walls and drainage structures," Mr Brayford said.
"We are similar to New Orleans because they were living below high-tide level."
As the clock ticks, the risk of catastrophe heightens.
Council and government staff are preparing another report on the situation.
It is expected to be received in council in the next few months and will outline the priority areas for the system, which stretches from Newstead to McKenzie St in Invermay.
Experts have been consulted for the study to determine different alternatives and their costs.
That study may be supported by a council trip to New Orleans and possibly Holland within the next six months.
"A tour would be useful to understand the complexities and difficulties facing us," Mr Brayford said.
Mr Brayford said the State Government's annual contribution of $150,000 for levees was spent on partial solutions.
Until more funding was assured, major works were not possible.
"We need substantial funds spent on them as soon as possible," the city's hydraulic modelling and systems manager Steve Ratcliffe said.
Concrete walls cost $7000sq.m to completely rebuild. There's already about 800m of work that needs to be done around the Inveresk railyards, York Park and the Queen Victoria Museum and Art Gallery - home to priceless and irreplaceable artefacts.
Other areas of concern are the concrete retaining wall running from Charles St Bridge along the North Esk River and the Kings Wharf mud box at the end of Forster St.
Mr Brayford said the majority of the earth levees were in better shape.
However, work is being carried out on the river edge pylons opposite Seaport to strengthen the earth levees too close to the river.
"If the ground is suitable it's the best method because you always know how much they've settled," Mr Brayford said.
"With concrete you never know what's underneath them."
