AS/NZS 1170.2 + local flood study · 18–46 pp typical

Flood Risk Report Explained — Plain-English Analysis (Australia)

Flood risk reports combine council flood maps, AS/NZS 1170.2 wind-and-flood loadings, 100-year ARI flood planning levels, and - increasingly - climate-adjusted projections out to 2100. For a buyer, the signal that matters is how far above the flood planning level the habitable floor sits, whether the property has overland flow paths through the yard, and whether the insurer will write affordable cover. We translate the hydraulic modelling into three numbers you can actually use: freeboard (in mm), exposure (in %), and estimated insurance premium impact (in $ per year).

Analyse my flood risk report View sample

What the report actually tells you

What’s in a flood risk report, plainly.

An Australian flood risk report typically cites the 1% AEP (annual exceedance probability, aka 100-year ARI) flood level from the relevant council or catchment authority flood study. It records the property’s floor levels relative to that flood planning level, any overland flow paths, flood-prone zones on title, and local-council planning controls that follow from the mapping. Engineering inputs come from AS/NZS 1170.2. The report rarely quantifies insurance impact directly; that’s a buyer-side calculation that we run against current Australian insurer risk pricing where data is available.

Common findings & what they cost

What we see in a flood risk report — with AUD ranges.

These are the five most common finding types we extract from flood risk reports, in descending severity. Each line is what the inspector flagged (in their words), translated into buyer-relevant English, and costed against current Australian trade rates.

Critical Habitable floor 250 mm below 1% AEP flood planning level; no freeboard. $35k–90k raise

Major Overland flow path crosses back yard; existing drainage undersized for event. $6k–18k drainage

Moderate Air-vent height below flood planning level - moisture ingress risk. $400–1,200 relocate

Moderate Flood-prone notation on title (Section 149 / planning certificate). disclosed

Minor Minor flood depth (<0.3 m) in 1% AEP event on driveway only. -

Negotiation · buyer’s checklist

Red flags & the questions to ask.

Red flags that usually kill a deal

Habitable floor level at or below the 1% AEP (100-year) flood planning level
An overland flow path crossing the building footprint or a habitable area
A flood-prone or flood-affected notation on the s149 / planning certificate
Recent flood events (2022, 2021) in the surrounding streets on BoM records

Questions to ask your vendor / agent / strata manager

What is the habitable floor level above the 1% AEP flood planning level (in mm of freeboard)?
Has the property flooded in the last 50 years, and is there photographic or insurance record?
Is flood insurance currently in place, and what does the renewal premium look like?
Are there any flood-mitigation works (levee, pumping, backflow valves) and who maintains them?

How ReportWise analyses this

Five passes. One engine. Flood Risk reports included.

Your flood risk report runs through the same five-pass pipeline as every other type we analyse: extract (OCR + structured parsing), classify (severity tagging against AS/NZS 1170.2 + local flood study), cost (AUD ranges against current Australian trade rates), translate (jargon to plain English), and validate (cross-check against the original so nothing is fabricated or omitted). Standard tier delivers in under sixty minutes; Premium tier in under thirty minutes or fifty percent refunded. Read the full method or compare tiers.

FAQ · Flood Risk reports

Answers we give every week.

Q.01What does "1% AEP" or "100-year ARI" actually mean?

They’re two ways of describing the same threshold - a flood level with a 1-in-100 chance of being exceeded in any given year. It doesn’t mean "once per century"; it means "each year, independent of every other year, there’s a 1% chance." Over a 30-year mortgage, the cumulative probability is roughly 26%.

Q.02Can I get flood insurance on a flood-prone property in Australia?

Yes, usually, but premiums rise sharply as the flood exposure rises. For properties with habitable floors below the 1% AEP level, annual premiums of $4,000–$20,000+ are not unusual. Some insurers decline new cover entirely in mapped high-risk zones. A broker quote before exchange is essential.

Q.03Does council flood mapping ever change?

Yes - councils periodically re-run flood studies with updated rainfall and catchment models, which can shift the flood planning level up or down. Some jurisdictions now incorporate climate-change projections. The report you’re buying may reflect the current study; the one in force at re-sale might be stricter.