Flood Risk in Sydney — What Buyers Need to Know

How NSW flood zones are defined

NSW councils identify flood-affected land through Flood Risk Management Studies. These studies model how water would flow through the catchment in floods of various magnitudes and produce mapped extents for each flood level.

The key flood levels you will encounter in Sydney planning documents are: the 1% AEP flood (also called the 100-year flood or 1-in-100-year event), which is the standard used in most planning controls; the 2% AEP (50-year) event; the 5% AEP (20-year) event; and the PMF, which is the largest flood considered physically possible.

Flood planning areas in NSW are generally defined as land below the 1% AEP flood level. Within a flood planning area, properties may be categorised as High Flood Risk (below the 1% AEP level), Medium Flood Risk (between the 1% and 5% AEP levels), or Low Flood Risk (above the 5% AEP level but below the PMF). Each council has its own policy on which categories trigger development restrictions.

What flood risk means for insurance

Flood insurance in Australia is voluntary but tied to the standard definition of flood (water inundating land that is usually dry, arising from an overflowing watercourse, lake, or ocean). Standard home and contents policies did not include flood cover until reforms following the 2011 Brisbane floods; today most policies offer it, but it is often excluded or priced separately.

For properties in identified flood planning areas, flood insurance premiums can be significantly higher — sometimes thousands of dollars per year rather than a few hundred. In the most severely flood-affected properties, insurers may decline to offer flood cover altogether, or may attach a flood excess of $10,000 to $50,000.

Before buying in a flood-affected postcode, obtain an insurance quote for the specific property — not just the suburb — and factor this into your ongoing holding cost. Some lenders will also require flood insurance as a condition of mortgage approval for properties in high-risk zones.

Flood risk and council planning controls

Properties in flood planning areas may face restrictions on what can be built or how existing buildings can be modified. Common restrictions include: minimum floor level requirements for new habitable rooms; requirements to elevate electrical switchboards, hot water systems, and HVAC above the design flood level; restrictions on basement car parks and underground storage; and, in the most severe cases, refusal of development applications for new dwellings.

For buyers of existing homes in flood areas, the planning controls mainly affect renovation potential and the ability to add granny flats or secondary dwellings. For buyers of vacant land or properties earmarked for redevelopment, the controls can materially affect the achievable gross realisable value and hence the price you should pay.

A Section 10.7 planning certificate (commonly called a 149 certificate) from the council will disclose whether a property is in a flood planning area. This certificate is typically obtained by your solicitor as part of the conveyancing process.

How Stickybeak measures flood exposure

Stickybeak calculates the percentage of each postcode's total land area that falls within the NSW Government flood hazard mapping. This gives a suburb-level signal: a suburb with 30% flood zone coverage is materially different from one with 2% coverage, even though both suburbs technically have some flood-mapped land.

This figure is a postcode-level aggregate — it does not tell you whether a specific property is in a flood zone. Always check the individual property against the relevant council flood map and obtain a flood certificate before exchanging contracts.

See this for your suburb

Related guides