Save You have reached your maximum number of saved items. Remove items from your saved list to add more. TOTOTO More than 20,000 homes in Melbourne’s western and southwestern suburbs are at new risk of flooding, according to new maps released by the city’s water authority. The draft maps, released on Thursday morning, note that
More than 20,000 homes in Melbourne’s western and southwestern suburbs are at new risk of flooding, according to new maps released by the city’s water authority.
The draft maps, released on Thursday morning, note that almost 15,420 homes in Hobsons Bay, which includes the suburbs of Williamstown, Altona and Spotswood, are susceptible to stormwater flooding in the event of significant rainfall. This marks a dramatic increase of almost eight times the previous figure of just 1,950 households at risk.
In neighboring Brimbank, which includes the suburbs of Deer Park, Derrimut, Sunshine and Taylors Lakes, the number of homes at risk has more than doubled, from 4,515 to around 11,820.
The draft maps are based on a “major rainfall event” that has a 1 percent chance of occurring in a given year. It is not intended to be a general representation of flooding in the area.
The maps are released as part of a two-year plan by Melbourne Water to update its flood modeling for each of the 38 metropolitan municipalities. They will replace older flood models, which were developed using outdated techniques.
They include a scenario for the year 2100, which predicts that around another 4,000 homes in Hobsons Bay (a total of 19,410) will be threatened, along with around another 3,000 homes in Brimbank (a total of 14,630).
In June this year, about another 20,000 homes in Banyule and Moonee Valley, in Melbourne’s northwest and northeast, were also considered at risk.
More than 60,000 properties in the northern hinterland councils of Darebin and Yarra were declared flood-prone in October 2025. Later that month, a further 32,000 homes were marked as at risk in Glen Eira and Merri-bek.
As part of its modeling, Melbourne Water assigns a hazard level to properties that are potentially at risk of flooding. The six rating levels tell residents how flooding might behave and the associated potential risk.
The lowest level (H1) indicates minimal, shallow flooding limited to low-lying areas. The highest risk level (H6) warns of deep, rapid flooding which is unsafe and can seriously damage buildings.
In Hobsons Bay, nine out of 10 homes flagged on draft flood maps are classified as H1 or H2, meaning they are generally considered safe for both people and buildings. Nearly 30 percent of homes in the area are affected by the flood mapping projects.
In Brimbank, more than eight in 10 affected homes also fall into the two lowest danger categories. About 13 percent of the homes in that area are marked as at risk on maps.
On Thursday, the maps were published on Melbourne Water’s online portal, detailing how to address the risk, mainly by preparing for stormwater. Homes marked on the flood maps will receive a letter from the water authority requesting comment during their consultation period on the maps.
“We encourage all Brimbank and Hobsons Bay residents and property owners to verify their address,” said Melbourne Water utility futures executive general manager Chris Brace.
“For most people, the preliminary maps will confirm that they are not at risk of flooding, or that their risk is lower than they expected. For those who are affected, we want to make sure they have clear and actionable information about what that means for their property.”
Community consultation on draft flood maps closes on 9 September.
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