Which Melbourne Suburbs Have the Most Homes Under a Flood Overlay?

Across 369 Melbourne suburbs, 65,158 of the 1,872,826 homes we counted (3.5%) have an address point inside a flood overlay on the Victorian planning map. The share differs from suburb to suburb: 88 suburbs have no flagged home, 35 have 10% or more of their homes in an overlay and 6 have 25% or more. Koo Wee Rup has the highest share (100.0%), and Elwood has the most homes in an overlay (3,658).

A flood overlay is a planning control: it changes what can be built and who must be consulted first. It is not a flood forecast, and it does not say that any particular home has flooded or will. This page counts homes rather than land. Data: Vicmap Planning flood overlays, 9 August 2026 · G-NAF addresses, 7 October 2026. General information, not financial, legal or insurance advice.

The headline numbers: how many Melbourne homes are in a flood overlay

We counted residential address points (each apartment is its own address, so this approximates homes) inside a Land Subject to Inundation Overlay (LSIO), a Special Building Overlay (SBO) or a Floodway Overlay (FO). These are the same three overlays behind the flood figure on each suburb page. An address inside any of them is "flagged" and counted once.

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By homes flagged, the SBO is the largest type (82% of flagged homes), then the LSIO (18%) and the FO (0%). The first three rows can overlap where one address sits in two overlays, so they need not add up to the last row.

Homes, not land: why counting addresses changes the picture

Delora's suburb pages report the share of each suburb's land under a flood overlay, which says little about how many homes are affected. Land can include creek corridors, reserves, farmland and industrial estates, and overlays are mapped around waterways and drainage systems (the LSIO's purpose, for example, refers to riverine and coastal areas). A suburb can be mostly overlay by area and have few homes inside it, or the reverse.

Of the 38 suburbs with 20% or more of their land under an overlay, the share of homes flagged is smaller than the share of land in 37. Bunyip has 58% of its land under an overlay but 3% of its homes. The biggest gaps among those suburbs:

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It can run the other way. Caulfield South has 27% of its homes inside an overlay but 14% of its land. That happens when homes are concentrated on the mapped part of a suburb. The biggest gaps that way:

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Suburbs with the highest share of homes in a flood overlay

Suburbs are ranked by the share of their homes inside a flood overlay, and only suburbs with at least 500 residential addresses are ranked. "Land under an overlay" is the suburb-page land measure.

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The 25 highest-share suburbs sit in 12 councils; Glen Eira has the most (6). Among the ten highest, the LSIO is the largest type in 3, the SBO in 7.

A suburb share is an average. Many streets in a high-share suburb are outside the overlay, and a few streets in a low-share suburb can be inside it.

Suburbs with the most homes in a flood overlay

Counting homes rather than percentages favours larger suburbs, because even a modest share of a big suburb is many households:

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Together, the ten suburbs with the most flagged homes account for 19,363 homes, or 30% of the metro total. At the top is Elwood, with 3,658 flagged homes, 35.6% of the 10,265 counted there.

Three overlays, three kinds of flood control: LSIO, SBO and FO

Land Subject to Inundation Overlay (LSIO)

Clause 44.04 says the LSIO identifies flood-prone land in a riverine or coastal area affected by the 1 in 100 (1 per cent Annual Exceedance Probability) year flood, or any other area the floodplain management authority determines. Melbourne Water says its flood planning controls are based on the extent of a flood of that size, which it describes as a flood with a one per cent chance of occurring in any given year (Melbourne Water). The LSIO has 11,774 flagged homes (18% of the total), and it is the largest type in 72 suburbs. The most LSIO homes are in Koo Wee Rup, South Yarra and Kensington. See the LSIO explainer.

Special Building Overlay (SBO)

Clause 44.05 says the SBO identifies land in urban areas liable to inundation by overland flows from the urban drainage system. Melbourne Water puts it as areas prone to stormwater or overland flooding when the capacity of the drainage system is exceeded. So the SBO is about the drainage system, where the LSIO is about riverine and coastal flooding. The SBO has 53,376 flagged homes (82%), and it is the largest type in 207 suburbs. The most SBO homes are in Elwood, Frankston and Seaford. See the SBO explainer.

Floodway Overlay (FO)

Clause 44.03 says the FO identifies waterways, major floodpaths, drainage depressions and high-hazard areas with the greatest risk and frequency of being affected by flooding. The clause lists the code as FO or RFO, and the count includes both. The FO has 29 flagged homes (0%), and it is the largest type in 2 suburbs. The most FO homes are in Epping, Pakenham and Wollert. See the FO explainer.

Who handles permits, and what is not counted

Melbourne Water says councils in the Port Phillip and Westernport region refer planning permit applications to it. Yarra's council says an application under either the SBO or the LSIO must be referred to the relevant floodplain authority, who is a determining authority and is usually Melbourne Water. The Urban Floodway Zone is a zone, not an overlay, so it is not counted; see the UFZ explainer.

How current is each council's flood mapping?

Vicmap Planning records a gazettal date against each flood-overlay polygon. We took each council's newest and median dates as recorded. It is a record-keeping field, not a quality score.

Across the 31 councils with recorded dates, each council's newest flood-overlay polygon was gazetted between November 2000 and June 2026, and the median polygon dates fall from 1999 to 2026. An older date does not make the mapping wrong, and a recent one can reflect a small boundary change rather than a new flood study.

Melbourne Water says it is constantly obtaining new flood information for the wider Melbourne area, and that changes to the flood information on council planning-scheme maps go through a Planning Scheme Amendment (Melbourne Water). So an overlay on a planning certificate shows the scheme as it stands, and Melbourne Water's own current data can be ahead of it. The table is ordered by homes flagged, not by date.

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What a flood overlay does, and does not, mean for a home buyer

What it does. Melbourne Water states that the SBO, LSIO and FO each require a planning permit for buildings and works, and that an applicant may need its consent before the council issues the permit (Melbourne Water). Building work on flood-affected land can also need the council's report and consent before a building permit is issued, so check with your council or building surveyor. Councils work with Melbourne Water to set a minimum floor level by adding a freeboard to the flood level (Melbourne Water). These rules are most likely to matter when renovating, extending or rebuilding.

What it does not. An overlay is a mapped planning control. It does not record whether a home has flooded, set a probability for that home, or give its floor height relative to a flood. A home outside every overlay has not been shown to be flood-free either.

Where it appears in a sale. A Victorian seller must disclose the zoning in the Section 32 vendor statement (see Delora's Section 32 guide). The overlays that apply are listed on the property's planning certificate, which a vendor's Section 32 statement draws on, so check the certificate itself (Planning Victoria). The Victorian Government's planning property report includes maps of the planning overlays affecting a property.

Flood level information. Melbourne Water issues property flood level certificates stating the estimated maximum floodwater height for a property, in metres to Australian Height Datum, for a flood with a one per cent chance of occurring in any given year. A certificate is valid for three months because the data can change, and is not approval for a development (Melbourne Water).

Insurance. Insurers use their own assessments, and a planning overlay is a planning control, not an insurance rating. CHOICE reported in October 2025 that insurers largely rate flood risk using the National Flood Information Database, which is based on studies and mapping contributed by local, state and territory governments, and that they also use other risk-rating tools customers cannot see (CHOICE). This page has no insurance data and says nothing about what any home would cost to insure.

How to check a specific address

A suburb figure cannot say what applies to one home. The usual steps:

• Address Check shows the zone and overlays mapped over a Victorian address, with sources. It is an indicative lookup of the same planning data, not an official statement.
• The explainers for the LSIO, SBO and FO cover what each overlay means for building.
• Melbourne Water issues property flood level certificates for a specific property, and the council can say what its planning and building rules require there.
• If the Section 32 includes a planning certificate, it is worth reading it against the planning scheme. The environmental risks guide lists the other hazard checks.

The planning certificate, the council and Melbourne Water are the authorities. Where this page or Address Check and an official source differ, the official source decides.

Method and limits

• Overlays: LSIO, SBO and FO (including the RFO code that clause 44.03 lists alongside FO) from Vicmap Planning, snapshot 9 August 2026. The Urban Floodway Zone is not counted.
• Unit: G-NAF address points with a reliability grade of 2 or better (geocoded to the property) inside a residential-category zone (the residential, township, mixed use, activity centre and comprehensive development zones). Apartments in central-city and commercial zones are left out, so homes there are undercounted.
• Flagged: the address point sits inside an overlay polygon. This is conservative: a lot with only a back corner in an overlay is not counted, although its planning certificate may still list the overlay.
• Scope: 31 metropolitan councils; suburbs with at least 500 residential addresses.
• Limits: this is not a flood forecast, history or probability for any one home, and council dates are Vicmap gazettal dates as recorded, not flood-study dates.

See Delora's method page for how sources and checks work. Related: the heritage overlay premium and the overlays guide. To report an error, use Corrections.

Frequently asked questions

How many Melbourne homes are in a flood overlay?

In this count, 65,158 of 1,872,826 homes (3.5%), across 369 suburbs and 31 councils. That is homes inside a mapped overlay, not homes that have flooded.

Which suburb has the highest share of homes in a flood overlay?

Koo Wee Rup, at 100.0% of 1,541 homes, followed by Tooradin (74.6%) and Elwood (35.6%). The last table on this page ranks every suburb.

Does a flood overlay mean my home will flood?

No. An overlay is a planning control that marks where flood-related rules apply. Melbourne Water says its flood planning controls are based on a flood with a one per cent chance of occurring in any given year, and an overlay does not say that a particular home has flooded or will.

What is the difference between the LSIO, SBO and FO?

The LSIO covers flood-prone land in riverine or coastal areas, the SBO covers land liable to flooding from the urban drainage system, and the FO covers waterways, major floodpaths and high-hazard areas.

Does a flood overlay affect insurance?

Insurers use their own assessments, and a planning overlay is not an insurance rating. This page has no insurance data, so only an insurer can say how an address is rated.

Why is the share of homes different from the land figure on a suburb page?

The suburb page measures land, including parks, farmland and creek corridors; this page measures homes. See the land-versus-homes tables above.

Full table: every suburb, ranked by share of homes in a flood overlay

All 369 suburbs in the count, highest share first. "Homes counted" is the residential address points used as the base. The LSIO, SBO and FO columns can overlap, so they need not sum to "In a flood overlay". Suburbs without a Delora page are shown without a link.

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