Glen Eira’s modelling includes stormwater drains managed by Melbourne Water and the council. Merri-bek’s mapping only accounts for Melbourne Water’s system because the local council recently completed its own analysis of its assets, finding 6503 properties were at risk.
Across the city, about 1500 kilometres of stormwater drains are managed by Melbourne Water and 25,000 kilometres belong to councils.
Before the Darebin and Yarra risk-rating system was unveiled, a blanket inundation overlay would be placed over properties regardless of their level of risk, foisting insurance cost rises, decreased house values and tough building restrictions onto home owners.
The state government hopes its new flood zone controls will help alleviate some costs for home owners if their property is classed as low risk. Its aim is also to equip developers with better information on how and where to build.
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Residents have been critical of the new modelling, arguing the new hazard ratings are of little use without a clear strategy for tackling flood risk and funding mitigation works.
Yarra councillor Kenneth Gomez will move a motion at Tuesday night’s council meeting calling on Melbourne Water to publish the methodology for its maps and extend the eight-week consultation period.
An example of new flood mapping for Glen Eira Council by Melbourne Water, showing parts of McKinnon and Bentleigh.Credit: Melbourne Water
He also wants the council to pursue state and federal funding for improving stormwater infrastructure.
Melbourne Water’s executive general manager of service futures, Chris Brace, previously told The Age that the leap in at-risk properties in Darebin and Yarra was because this was the first time the entire stormwater system was being modelled.
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“Historically, flood management in Melbourne has focused on waterway flooding, but as we see climate change and rainfall intensity change, the risk of stormwater flooding is increasing,” Brace said at the time.
Melbourne Water is proposing to almost double the investment on drainage management to $300 million over the next five years.
Maps for Glen Eira and Merri-bek council areas will be finalised after community consultation ends on December 5.