Checking flood risk before buying in Queensland: what the maps tell you

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Kooky

Builder of Shaka, the payment router that pays every agent their commission on closing date.

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Most of Queensland's towns and cities sit beside a river, a creek or the sea, and a large share of the state's homes are built on land that water has reached before or could reach again. Brisbane City Council says it plainly in its own material: the city is built on a floodplain, so flooding cannot be prevented. For a buyer, the question is never whether floods happen in Queensland. It is whether this particular block is likely to be affected, how often, and what that does to the cost of owning the home.

The answer is public, but it is scattered. The State runs one mapping tool, each council runs its own, and they do not show the same things. The seller's paperwork, meanwhile, is silent on the subject. This guide sets out who is responsible for telling you what, how to read the main maps, what the percentages mean over the years you will own the home, and where the maps stop being useful.

Why the flood check falls to the buyer

Since 1 August 2025, a seller of Queensland property has had to hand the buyer a disclosure statement before the contract is signed. The scheme was created by the Property Law Act 2023 and applies to homes, commercial property and vacant land. The statement covers a defined list of matters: who the seller is, the title and what is registered against it, zoning, listings on environmental and heritage registers, whether there is a pool, certain building notices and, for units, body corporate information.

The Queensland Government's summary of the scheme is just as clear about what falls outside it.

This surprises many buyers, particularly those arriving from other states. A statement that runs to several pages and attaches a title search feels comprehensive. On flood it is not, by design. The scheme tells the buyer what is recorded on certain registers. Flood exposure is recorded on maps, held by councils, and the buyer is expected to look.

The scheme does give a buyer a right to end a contract where the statement is missing, or inaccurate or incomplete on a material matter the buyer did not know about. That right relates to the things the statement must contain. Because flood history is not one of them, its absence from the statement is not a defect.

Four kinds of flooding, mapped separately

"Flood" covers several different events, and a property can be exposed to one and untouched by the others. Brisbane City Council's Flood Awareness Map separates four sources.

River flooding is the slow, large-scale kind: long rain over a big catchment, a river that rises over days and stays high. Creek flooding is faster, because creek catchments are small and respond within hours of heavy rain. Storm tide flooding comes from the sea, when a storm pushes water onshore on top of the tide; it affects bayside and coastal suburbs and the lower reaches of tidal rivers.

The fourth is overland flow, and it is the one buyers most often overlook. Overland flow is rainwater running across the ground on its way to a drain or creek during an intense downpour. The Council describes it as flooding that can occur rapidly and unpredictably. It does not need a waterway nearby. A house halfway up a hill can sit in an overland flow path if the land behind it funnels water through the yard.

The distinction matters because the maps treat the sources differently, the warning times differ, and insurers may price them differently. A buyer who checks only for the river, because the river is what made the news, has done a quarter of the job.

FloodCheck: the State's starting point

FloodCheck Queensland is the State Government's flood mapping application. It is operated by the Department of Natural Resources and Mines, Manufacturing and Regional and Rural Development and draws on data collected through the Queensland Flood Mapping Program. It brings together floodplain data, modelled flood maps, historic flood maps, imagery and flood study reports from across the state.

Its value is breadth. For a town with a small council and limited online mapping, FloodCheck may be the only place a buyer can quickly see whether a flood study exists and what historic flood lines have been recorded. For someone comparing regions, it gives a first impression of where the floodplains are.

Its limits are stated on its own front page, and they are worth reading before relying on anything it shows.

Two further cautions appear in its terms. Much of the flood data is historic, so it may predate new development, drainage works or revised studies. And the tool is not to be used in a disaster or emergency. The department also notes that a new FloodCheck Information Portal is being developed to replace the current application, so its appearance and content may change.

Treat FloodCheck as a way to learn that a question exists. The answer to the question is held by the council.

Council maps: where the property-level answer is

Local governments are responsible for flood information at the level of the individual property. They commission the flood studies, they write the planning rules that follow from them, and most of the larger councils publish an interactive map that can be searched by address. The names differ from one council to the next: a flood awareness map in Brisbane, a flood portal in Logan, a flood search or flood report elsewhere.

Brisbane's map is a good example of how these tools are organised. It uses two different ideas. For river, creek and storm tide flooding it shows likelihood: the chance that flooding from that source reaches the land in any one year. There are four bands, labelled high, medium, low and very low, which correspond to annual chances of 5 per cent, 1 per cent, 0.2 per cent and 0.05 per cent.

For overland flow it shows impact instead. High-impact areas, which the Council associates with a 5 per cent annual probability, are described as generally unsafe for people, vehicles and buildings. Medium-impact areas, at 2 per cent, are unsafe but flood less often. Low-impact areas, at 1 per cent, are described as generally safe with some variable hazards.

The Council is direct about what the map leaves out. It does not give the depth of floodwater or its speed. A lot shaded "medium" might take a few centimetres across the back fence or a metre through the living room, and the colour alone cannot say which.

Logan City Council's approach shows a second design. Its Flood Portal produces a Property Flood Report for an address, and its mapping concentrates on the flood with a 1 per cent chance in any year, which the Council also calls the 1 in 100 flood. Information on rarer events, down to a 0.05 per cent annual chance, is kept for emergency planning. The Council notes that it has applied a modest allowance for climate change to its modelling, in line with Brisbane and the Gold Coast.

What a percentage means over the years you own the home

The percentages on a flood map are annual. Planners call the measure annual exceedance probability: the chance that a flood of at least that size occurs in a given year. A 1 per cent flood is one with a one-in-100 chance each year, which is where the older phrase "one-in-100-year flood" comes from.

That phrase misleads. It suggests a flood that arrives once a century and then leaves the area alone for another hundred years. In fact the chance is the same every year, whether or not a flood happened the year before. Two such floods can occur a few years apart.

What a buyer needs is the chance over the period of ownership. The arithmetic is simple: the chance of no flood in one year, multiplied by itself for each year, subtracted from one. Over 30 years, the length of a standard home loan, the annual figures on Brisbane's map turn into the following.

A "medium" property is therefore not a remote risk for someone taking out a 30-year loan: on this arithmetic there is about a one-in-four chance of at least one flood of that size during the term. A "high" property is more likely than not to flood within a decade or two. The lower bands remain genuinely unlikely for any single owner, which is why they matter more to emergency planners than to household budgets.

The calculation assumes the annual chance stays constant. Councils revise their studies as rainfall data and climate projections change, so the bands themselves can move.

Property flood reports and flood levels

Beyond the coloured map, several councils will produce a report for a single lot. Brisbane has its FloodWise Property Report and Logan its Property Flood Report; other councils offer a flood search for a fee or free of charge. These reports are the documents a conveyancer, a building designer or an insurer is most likely to want to see.

The useful content of such a report is usually a set of levels. A flood study estimates how high the water would reach in a flood of a given likelihood, expressed as a height above a fixed reference. The same reference is used for the ground level of the lot and, where known, the floor level of the house. Comparing the three tells a buyer far more than a colour does: whether the modelled flood would cover part of the yard, reach the slab or stop short of the building altogether.

Reports may also record the levels reached in past floods at that location, and the minimum floor height the council would require for new habitable rooms. That last figure is a planning requirement. It shows what would be asked of anyone building or extending on the lot.

A report is only as current as the study behind it. Logan City Council puts the point fairly: flood studies use the best available information at the time they are undertaken, and are refreshed over time with new rainfall data, elevation surveys and climate projections.

The overlay: what a flood notation does to building plans

A council flood map has a second life inside the planning scheme. Land identified as flood-affected is placed in a flood overlay, and the overlay switches on a set of rules for development.

Law firm Mullins, in a note for buyers published in November 2025, summarises the usual effects: a flood overlay may dictate minimum floor levels, require flood-resilient materials or, in some locations, prevent building work entirely. For a buyer who plans to raise, extend or rebuild, these rules can decide whether the project is possible and what it costs. A granny flat under a high-set house, for instance, may fall below the level at which habitable rooms are allowed.

The overlay is also what a lender's valuer and a future buyer's conveyancer will find. Even an owner with no plans to build inherits its effect on resale.

It is worth separating the overlay from the hazard. The overlay is a regulatory line. It can be drawn generously or tightly depending on the policy of the council, and it can be redrawn without any change in the physical risk.

Maps change, in both directions

Two decisions in South East Queensland show how much a map can move.

In 2025, Brisbane City Council updated its creek flood mapping after completing new flood studies for the Breakfast Creek, Jindalee and Lota Creek catchments. Trade publication Inside Local Government reported that the update affected 17,246 properties: 10,129 were added to mapped flood areas, 400 were removed and the remainder changed category. The changes applied to creek and waterway flooding only, not to the Brisbane River or overland flow, and were written into Brisbane City Plan on 19 September 2025. For some of the newly mapped lots, the Council said, the exposure was as low as a one-in-2,000-year event.

Logan has moved the other way. After an earlier update brought very rare scenarios into its maps and drew strong objections from residents, the Council endorsed a set of changes at a special meeting on 4 June 2026. The central one is to remove from its flood overlay every event less likely than the 1 per cent annual chance flood, including the most extreme scenario, known as the Probable Maximum Flood. The change is subject to further approvals, and the rarer scenarios are to be kept for emergency planning.

The lesson for a buyer is that the date on a flood search matters. A report obtained by the seller two years ago, or a screenshot in a listing, may describe a map that no longer exists. And a property that is unmapped today can be mapped tomorrow if a new study is completed for its catchment.

Insurance is a separate test

A council map and an insurance premium are connected less closely than most people assume. Councils map flooding to plan land use and emergency response. Insurers price the chance of a claim at one address.

When Logan's mapping changes prompted complaints about premiums, a spokesperson for the Insurance Council of Australia told trade publication Insurance Business in October 2025 that each insurer uses its own datasets and risk assessment capabilities beyond local council flood maps, with most calculating premiums at an address level. Logan City Council makes the matching point from its side: it does not set premiums or determine how insurers price risk.

That report included a Logan household quoted $10,500 a year for cover. A figure of that size changes what a property costs to hold, and it can affect borrowing too. Mullins notes that properties in mapped flood areas often face higher premiums or limited availability of cover, and that loan terms generally require the borrower to keep the home adequately insured.

The Queensland Government's advice to buyers is that insurance should usually be in place from the contract date. That makes an insurance quote, with flood cover priced in, a natural part of the checks made before signing or during any conditional period, not a task for settlement week.

Putting the checks in order

None of this takes long, and most of it is free. The sequence below is one sensible order, moving from the broad picture to the specific lot.

Where in the purchase these steps fall depends on how the home is being sold. A flood search does not, of itself, give a buyer any right to withdraw from a contract. If a buyer wants the purchase to depend on what a search or an insurance quote reveals, that has to be written into the contract before it is signed, and at an auction there is no opportunity to add conditions at all. This is a matter to settle with a solicitor or conveyancer before making an offer.

What the maps cannot tell you

Even the best council mapping has edges, and a buyer should know where they are.

Maps model the flood that the study was asked to model. Blocked drains, a neighbour's new retaining wall or a development upstream can change how water behaves on one street without altering the study. Overland flow mapping in particular is sensitive to small features of the ground.

Maps do not show consequences. Brisbane's map gives no depth and no velocity. Two homes in the same band can have very different experiences depending on floor height, construction and where the water enters.

Maps are not history. A property outside every mapped area may still have taken water in an unusual storm, and a mapped property may never have been wet in living memory. Neighbours, the building inspector and the house itself are sources too: water marks under a high-set house, new plasterboard to a consistent height, or a line of replaced skirting boards are all worth a question.

And maps are a snapshot. Councils revise them as studies are completed and as policy changes, in either direction, as Brisbane and Logan have shown within a single year.

Used with those limits in mind, the maps do the job the seller's disclosure statement leaves undone. They will not tell a buyer whether to buy. They will tell a buyer what question to put to the insurer, the conveyancer and the building designer before the contract is beyond recall.

Kooky, from Shaka

Kooky edits Queensland Estate and builds Shaka, the payment router he made for Queensland property professionals. One payment comes in, and every agent, agency and party in the deal receives their signed share on closing date.

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