Will my house flood? How to check your property's flood risk in Australia

Will my house flood? How to check your property's flood risk in Australia

"Will it flood?" is probably the most consequential question you can ask about an Australian property, and it's one the public maps were never really designed to answer. A council flood study exists to guide planning decisions across a whole catchment. What a buyer or owner wants to know is narrower and more personal: will water get into this particular house, how deep, and how often?

The two questions overlap, but they aren't the same. This guide covers how to check your flood risk without paying anyone, where the free maps genuinely fall short, and how a flood classification flows through to your insurance bill.

The three kinds of flooding

Flooding tends to be discussed as a single hazard, but water reaches a property along three quite different paths, and two houses on the same street can face very different combinations of them.

  • Riverine flooding happens when a river or creek bursts its banks after heavy rain. It typically builds over hours, sometimes days, and it's the hazard most council flood maps are built around.
  • Flash (overland) flooding happens when intense local rain overwhelms the drainage system and runs downhill along roads and low points, often nowhere near a watercourse, with little or no warning. Because council mapping is generally organised around rivers and creeks, many properties exposed to overland flow never appear on a flood map at all.
  • Coastal flooding occurs when tides, storms and surge push seawater across low-lying land, a problem that sea-level rise is steadily making worse.

The distinction matters in practice. When someone tells you a property "isn't in the flood zone", they almost always mean the riverine zone, which covers only one of the three ways water can arrive.

How to check your flood risk for free

These checks are worth doing before you pay for any assessment.

  1. Your local council. This is the primary source. Most councils publish flood maps or planning overlays online, and some offer a property-specific flood report for a small fee.
  2. Your state government. Searching for "your state flood map" will usually surface the aggregated state overlays.
  3. The Australian Flood Risk Information Portal (AFRIP). Geoscience Australia's national catalogue of flood studies is most useful for one specific job: confirming whether a formal study even exists for your area. (Note that the contributed studies largely run to 2018.)
  4. The property's history. Ask the agent, talk to the neighbours, and look up what has happened in the suburb before. Local memory often records floods that the official mapping doesn't.

When you do find a map, two details are worth checking that most people skip: the date of the underlying flood study, and whether the map shows flood depth or only flood extent. A recent study with depth information can tell you roughly how bad a design flood would be at your block. An older extent-only outline tells you little more than that the area has been wet before.

Are Australian flood maps accurate?

They're accurate for what they were designed to do, which is a narrower job than most buyers assume.

Australia does have a shared national method for estimating floods, called Australian Rainfall and Runoff (ARR). What it doesn't have is a single, regularly updated national flood map. Councils commission their own studies as budgets allow, and the Planning Institute of Australia has described the result as a patchwork applied inconsistently: some councils maintain detailed online mapping, while others still rely on studies drawn decades ago.

There's no fixed update cycle either. In practice, a flood study gets refreshed when funding arrives, when a major flood forces the issue, or when a town plan comes up for review, which means the map you're reading may be considerably older than the website hosting it.

It's also worth being clear about what the maps actually measure, because the terminology misleads people. The standard benchmark is the 1% Annual Exceedance Probability (AEP) flood, meaning a flood with a 1% chance of being reached or exceeded in any given year. Its older name, the "1-in-100-year flood", suggests a once-a-century event, but the statistics say otherwise: over a 70-year period there is roughly a 50% chance of experiencing at least one, and nothing prevents two from arriving in the same decade.

From that design flood, councils set a Flood Planning Level, usually the design flood height plus a safety margin known as freeboard, which governs how high the floors of new buildings must sit. It reads like a technicality, but it's the quiet number that decides whether a block is cheap or expensive to build on.

The most significant limitation, though, is that most maps model the past climate rather than the future one. Rainfall intensities once treated as a worst case are increasingly looking like a lower bound, and a flood map built on a 1990s study can classify a property as low-risk using assumptions the climate has already moved beyond. For a purchase measured in decades, that gap between the mapped climate and the coming one is where much of the real risk sits.

How flooding affects your insurance

In Australia, your premium tracks your assessed flood risk, and insurers don't simply copy the council map. They blend it with their own address-level data and claims history, and their models tend to move faster than the public mapping does.

The scale of the issue is substantial. The Insurance Council of Australia estimates around 1.36 million properties face some level of flood risk, and Climate Valuation projects that more than 500,000 homes could be at high risk of becoming effectively uninsurable for flood by 2030, with cover either withdrawn or priced out of reach.

Logan City Council offered a recent illustration of how quickly this can land on homeowners. In late August 2025, the council wrote to around 20,000 residents whose flood-risk classification had shifted under updated mapping for its draft town plan, and some were subsequently quoted $17,000 to $30,000 for insurance. The mapping became a flashpoint partly because it modelled extraordinarily rare events, including a 1-in-2,000-year scenario and the Probable Maximum Flood, a decision that has since triggered an independent review and a Queensland state planning-policy review. The council doesn't set premiums, of course, but that distinction offers little comfort when a new map redraws the line through your block.

Two consequences are worth sitting with:

  • A re-mapping can lift your premium even if your house has never flooded, because insurers price on risk classification rather than on your individual history.
  • Homes that become uninsurable also become hard to finance and hard to sell, since lenders usually require valid cover.

This is the practical case for understanding your true property-level risk before you buy: not the suburb headline, but the number on your block.

What you can do if you're in a flood zone

A flood zone classification narrows your options, but it doesn't remove them. Which measures make sense depends heavily on the depth, frequency and duration of flooding at your block, along with how the house is built, which is why it's worth confirming any plan with a building professional. Broadly, though, the options fall into four groups.

  • Raise what matters. Lifting an entire home works well for lightweight houses on stumps, though brick construction generally can't be raised. Even where the house stays put, the services can be lifted: power boards, hot water systems, air-conditioning units and washing machines all survive a flood far better off the floor.
  • Wet-proof. This approach accepts that water will get in and concentrates on limiting the damage: sealed concrete or tiles instead of carpet, single-skin walls, composite mouldings, waterproof membranes, and louvres that let water pass straight through. The result is a faster, cheaper clean-up rather than a dry house.
  • Dry-proof. Seals and barriers can keep water out entirely, but only for shallow, short-duration floods. Beyond that, water pressure and seepage win.
  • Absorb. Permeable surfaces, rain gardens and planting slow overland flow across the block, which targets exactly the kind of flash flooding that council maps tend to miss.

None of these measures guarantees a dry house in an extreme event. The real aim here is to decrease damage, a faster recovery, and a property that stays insurable.

The takeaway

The free maps are worth using, provided you read them for what they are. They're a patchwork built largely around rivers, they're often years out of date, and most of them model a climate we're already leaving behind. They answer the planning question, whether an area is flood-prone, reasonably well. They were never built to answer the question that matters most to an owner: will water get into this house, how deep, and how often?

Answering that property-level question is precisely the job of a dedicated resilience assessment.

Frequently asked questions

Is my house in a flood zone?

Start with your local council's online flood map or planning overlay, then check your state flood portal and the property's history. Keep in mind that "flood zone" usually refers to riverine flooding only, so flash and coastal flooding may not appear on the map at all.

What does a "1-in-100-year flood" actually mean?

It's the older name for the 1% AEP flood, a flood with a 1% chance of being reached or exceeded in any given year. It doesn't mean once a century: over a 70-year period there's roughly a 50% chance of at least one, and two can occur within a single decade.

Will being re-mapped into a flood zone raise my insurance?

It can, even if your home has never flooded, because insurers price on risk classification rather than individual history. The 2025 Logan City Council re-mapping, which left some residents facing quotes of $17,000 to $30,000, shows how sharply a classification change can move a premium.

Can a property become uninsurable for flood?

Yes. Cover can be withdrawn, or priced so high that it's effectively out of reach. Climate Valuation projects that more than 500,000 Australian homes could be at high risk of this by 2030, and uninsurable homes are also harder to finance and sell.

Does raising my house guarantee it won't flood?

No. Even a home raised to the Flood Planning Level can be overtopped in an extreme event. Resilience measures aim to reduce damage and speed up recovery rather than promise a dry house.

Thinking about a specific property? A resilience report from Green Building Consultants assesses flood, climate and hazard exposure for your exact address, and what it means for you. You can find out more about our reports here or Order a report →

Sources & further reading

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