Adelaide Hills: what the bushfire and flood overlays actually say

Every residential suburb in the Adelaide Hills sits inside a bushfire hazard overlay. All of it, not part of it. So the question "is this block bushfire prone?" has the same answer everywhere in the Hills, and it is not the useful question. The useful ones are which bushfire class the block falls in, and whether anyone has actually mapped the creek at the bottom of it.

This walks through what South Australia's Planning and Design Code overlays say about a Hills block, what they do not say, and which of the two hazards is the one most buyers get wrong.

The one-minute version

• The Code splits bushfire hazard into classes. Across the Hills the relevant ones are High Risk and Medium Risk, and the split between them varies a lot from suburb to suburb: Mylor and Upper Sturt are entirely High Risk, Woodside is mostly Medium.
• Flooding is the opposite problem. Most of the Hills is covered by Hazards (Flooding - Evidence Required), which is not a flood map. It means no flood mapping exists here and the burden of proving the land is safe sits with whoever applies to build.
• So a Hills suburb showing a low mapped flood share is not a suburb with low flood risk. It is usually a suburb nobody has modelled.
• Mount Barker is the exception. It has a real council flood study with 5%, 2%, 1% and 0.2% AEP extents and hazard classes, which is a different and much better kind of information.

The bushfire overlay: the class is the whole story

The Planning and Design Code maps bushfire hazard in named classes. In the Hills you will meet two of them, and where a block falls decides the construction standard, the access and water supply requirements, and often whether an insurer wants a conversation.

Measured against the locality boundaries in September 2026, the split runs like this:

Suburb	High Risk	Medium Risk
Mylor	100%	-
Upper Sturt	100%	-
Hahndorf	90%	10%
Nairne	84%	16%
Littlehampton	77%	23%
Crafers	72%	28%
Bridgewater	71%	29%
Aldgate	65%	35%
Lobethal	60%	40%
Stirling	55%	45%
Balhannah	51%	49%
Mount Barker	47%	53%
Woodside	22%	78%

Two things follow from that table.

First, a suburb-level number does not classify your block. Stirling is close to an even split, so two blocks a street apart can land in different classes. The overlay boundary matters, and it is mapped, so it can be checked for the actual lot before you make an offer.

Second, the class is a planning trigger, not a building specification. It tells you the development pathway and the assessment your application faces. The actual construction standard for the house comes from a bushfire attack level assessment under AS 3959, done at the lot with its own slope, vegetation and separation distances. A High Risk block with a cleared paddock to the north is not the same build as a High Risk block with a gully of stringybark on its downhill boundary.

The flood overlay: "Evidence Required" is not a flood map

This is the one that catches people. The Code overlay covering most of the Hills is Hazards (Flooding - Evidence Required). In plain terms it says: this land has not been flood mapped, and if you want to develop it, you have to produce the flood information yourself.

It blankets the region. Nairne, Littlehampton and Macclesfield are 100% covered by it. Crafers is 99.9%, Woodside and Lobethal about 97%, Balhannah 92%, Hahndorf 80%.

Because it makes no claim about which land floods, we do not count it as mapped flood hazard on a suburb profile, and neither should you. If we did, every Hills suburb would read as almost entirely flood affected, which would be both alarming and meaningless.

What is left once you take it out is the small amount of genuinely mapped flood hazard, which follows the watercourses:

Suburb	Mapped flood hazard
Mylor	4.7%
Bridgewater	3.9%
Hahndorf	2.6%
Aldgate	2.3%
Stirling	0.8%
Crafers, Nairne, Littlehampton, Macclesfield	0.0%

Read those zeroes correctly. Nairne at 0.0% is not a dry suburb. It is a suburb where the only flood layer that reaches it is the one that says "nobody has looked". The creek is still there, and a steep Hills catchment concentrates runoff fast.

Mount Barker is the exception, and it shows what good looks like

Mount Barker District Council has published a real flood study, and it changes the character of the information completely. Instead of one blanket overlay you get four event extents and a hazard grading:

• 5% AEP (a 1-in-20 year event) covering about 3.9% of the locality
• 2% AEP about 5.0%
• 1% AEP (the 1-in-100 year event most planning decisions turn on) about 6.0%
• 0.2% AEP (1-in-500) about 8.5%
• Hazard classes from Low through to Extreme for both the 1% and 0.2% events

That is enough to answer a real question: not just "does this lot flood", but "in which event, and how dangerous is the water when it happens". The gap between the 1% and 0.2% extents also tells you how quickly the flood grows once the design event is exceeded, which is worth knowing for a block that sits just outside the line.

What to check before you buy in the Hills

1. Get the bushfire class for the lot, not the suburb. The overlay boundary is mapped. In a suburb near an even split, this is a genuine difference in what you will be asked to build.
2. Walk the low corner and look for the watercourse. Where the only flood layer is "Evidence Required", the mapping will not help you and your eyes will. Defined channel, debris lines, culvert sizes under the driveway.
3. Check whether your council has a flood study at all. Mount Barker District Council does. Adelaide Hills Council, at the time of writing, does not publish one that reaches these suburbs.
4. Expect a flood assessment cost if you are developing. "Evidence Required" means exactly that, and on an unmapped catchment the evidence has to be generated.
5. Check the water catchment and vegetation overlays too. Most of the Hills sits in the Mount Lofty Ranges Water Supply Catchment and carries native vegetation and significant tree controls. These do not appear in a bushfire or flood search but they shape where a house, driveway and wastewater system can go.
6. Remember the ground is different up here. Hills blocks sit on rock, not on the plains clay. What is under an Adelaide block covers what that means for footings and excavation.

Common questions

Is all of the Adelaide Hills bushfire prone? Yes, in the sense that the residential suburbs are entirely inside a mapped bushfire hazard overlay. What varies is the class. Some suburbs, such as Mylor and Upper Sturt, are wholly High Risk; others, such as Woodside, are mostly Medium Risk.

What does "Hazards (Flooding - Evidence Required)" mean on a South Australian property? It means the land has not been flood mapped and a development application has to supply flood information before it can be assessed. It is a procedural requirement, not a statement that the land floods, and it is not evidence that the land is safe either.

Why does my Adelaide Hills suburb show 0% flood? Because the only flood layer covering it is the Evidence Required overlay, which we exclude from mapped flood hazard for the reason above. It means unmapped, not unaffected.

Which Adelaide Hills councils have real flood mapping? Mount Barker District Council publishes flood extents for the 5%, 2%, 1% and 0.2% AEP events with hazard classes. Elsewhere in the Hills the Code overlay is generally all there is.

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Check the bushfire class, the flood overlays, zoning and the rest for a specific Adelaide Hills address. Get a Property Report, or browse the South Australian suburb profiles first.

LayeredGeo compiles planning overlays, geology, soils and site data into automated property and geotechnical reports for addresses in Queensland, New South Wales, Victoria and South Australia.

About this article. Published by LayeredGeo. It is general information about how property and ground conditions are assessed in Australia, not engineering, planning, legal or financial advice, and it is not specific to any property. Check anything that matters against the source dataset or a suitably qualified professional before you rely on it. If you spot something wrong, tell us at hello@layeredgeo.com.au and we will fix it.

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