Building on Flood-Prone Land in NSW: What Changed After 2022

If you are buying, subdividing or building on land anywhere near a river, creek or overland flow path in NSW, the rules you are working under today are not the rules that applied a few years ago. The catastrophic floods of 2022 forced a hard look at how the state manages flood risk, and the changes that followed now flow directly into how councils assess development applications on flood-prone land.

This article walks through what actually changed, why it matters for builders, developers and rural landowners, and what you should be doing differently before you commit to a site or lodge a DA.

The 2022 floods: the event that reset the conversation

The floods of February and March 2022 in the Northern Rivers, followed by further major flooding in July 2022 across the Hawkesbury-Nepean and other catchments, were among the worst in NSW history. Whole town centres in the Northern Rivers went under. Communities in Western Sydney that had been flooded the previous year were inundated again. For many property owners, it was the second or third flood in eighteen months.

In response, the NSW Government commissioned the 2022 NSW Independent Flood Inquiry, led by Professor Mary O’Kane and Michael Fuller. The inquiry examined how the floods unfolded, how prepared the state was, and how land use planning had allowed so much development in harm’s way. Its findings drove a wave of policy change that is still working its way through the planning system.

For anyone in the development industry, the message from the inquiry era is simple: flood risk is now taken more seriously at every stage of the planning process, and the documentation expected with a DA on flood-affected land has become more rigorous.

The new Flood Risk Management Manual replaced the 2005 manual

The most significant structural change came in June 2023, when the NSW Government gazetted the Flood Risk Management Manual. This replaced the Floodplain Development Manual that had been in place since 2005 – a document that predated not just the 2022 floods but almost two decades of growth in flood modelling capability and climate understanding.

The new manual is not a standalone document. It comes with a toolkit of supporting guidelines covering:

• Flood modelling – how flood studies should be undertaken and what they should produce
• Floodplain categorisation – how land is classified by hazard and hydraulic function
• Risk and emergency management – how evacuation and isolation risks are assessed
• Land use planning advice – how flood risk should inform zoning and development controls

Under the NSW flood prone land policy, councils remain responsible for managing flood risk on floodplains in their local government areas. The manual guides how they do that: it shapes their flood studies, their floodplain risk management plans, and the floodplain risk management committees that oversee the process. Over time, as councils update their studies and plans in line with the new manual, you can expect the flood information attached to individual properties – and the controls applied to them – to be refreshed.

The legal machinery caught up too

A manual on its own does not change the law. That is why the Environmental Planning and Assessment Amendment (Flood Planning) Regulation 2023 matters. It updated the references in the planning legislation – including Schedule 9 of the EP&A Regulation – from the old 2005 manual to the new Flood Risk Management Manual. That includes the definitions that do real work in a development assessment, such as “flood planning area” and “probable maximum flood”.

In practical terms, this means that when your council, your certifier or your consultant refers to flood planning concepts in a statutory context, they are now anchored to the 2023 manual. If your project documentation still cites the 2005 Floodplain Development Manual, it is out of date and a council assessment officer will notice.

The shift from the 1% AEP to the full range of flood risk

One of the most important changes in thinking – accelerated by the 2022 events – is the move away from treating the 1% AEP flood (the old “1-in-100-year flood”) as the only event that matters.

The probable maximum flood (PMF) is the largest flood that could conceivably occur at a location. It defines the outer extent of flood-prone land. Historically, many councils focused their development controls almost entirely on the 1% AEP event, with the PMF treated as a theoretical upper bound. That is changing. Councils increasingly consider risk across the full range of floods up to the PMF, particularly for:

• Emergency response planning – can occupants evacuate before floodwaters cut access, or will they be isolated on a shrinking island of high ground?
• Vulnerable land uses – childcare centres, aged care facilities, seniors housing, schools and hospitals face far tighter scrutiny, because their occupants cannot self-evacuate quickly.

For a standard dwelling on land above the 1% AEP level but below the PMF, this does not necessarily mean you cannot build. It does mean questions about evacuation routes, rising road access and shelter-in-place may be asked where they previously were not.

What “flood-prone” actually means for your DA

If your site is identified as flood-affected, here is what you should expect the DA process to involve.

A flood study or flood impact and risk assessment

Most councils will require a flood impact and risk assessment (sometimes called a flood report or flood statement) prepared by a suitably qualified civil engineer. Depending on the site and the council’s existing flood information, this can range from a short report interpreting council’s adopted flood levels through to detailed hydraulic modelling of how your proposal interacts with flood behaviour. The assessment typically addresses:

• The flood levels, depths, velocities and hazard categories affecting the site
• How the proposed development sits relative to the flood planning level
• Whether the development adversely affects flood behaviour on neighbouring land
• Structural adequacy of buildings exposed to flood forces
• Evacuation and emergency response arrangements

Flood planning levels and floor levels

Your habitable floor levels will need to meet the council’s flood planning level, which is generally a defined flood event plus a freeboard allowance. This affects building design, driveway grades, and sometimes the feasibility of the whole project – a floor level a metre above natural ground changes the streetscape, the access arrangements and the cost of the build.

Filling restrictions

Raising a site with fill sounds like the obvious fix, but on a floodplain, fill displaces flood storage and can redirect flood flows onto other properties. Councils control filling on flood-prone land tightly, and in some hydraulic categories filling is effectively prohibited. Any proposal to fill needs engineering justification showing it will not worsen flooding elsewhere.

Evacuation considerations

Expect questions about how occupants get out. Is there rising road access to flood-free ground? How much warning time does the catchment provide? For fast-responding creeks and overland flow paths, warning time can be minimal, which pushes the assessment toward the safety of the building itself.

Buying flood-affected land: due diligence is not optional

The 2022 floods proved that plenty of land bought in good faith carried far more flood risk than the purchasers understood. Before you exchange on a site, do the homework:

• Read the planning certificate carefully. The section 10.7 planning certificate flags whether flood-related development controls apply to the land. It is the first and cheapest signal that flooding is a live issue.
• Request council’s flood information. Most councils will provide adopted flood levels and mapping for a property on request, drawn from their flood studies.
• Understand which flood affects the site. Land can be clear of the 1% AEP event but well within the PMF extent – which may still trigger evacuation and vulnerable-use considerations.
• Get engineering advice before you commit. A civil engineer can tell you what floor levels, filling limits and access constraints are likely, and whether the development you have in mind is realistic on that site. Finding out after settlement is an expensive way to learn.

For rural landowners, the same logic applies to sheds, dwellings and farm infrastructure. A house site that looked fine in a dry decade may sit squarely in a floodway, and councils are far less inclined to wave that through than they once were.

Where a civil engineer fits in

Flood-affected sites are fundamentally an engineering problem wrapped in a planning process. A civil engineer’s role typically includes:

• Obtaining and interpreting council flood information and existing flood studies
• Preparing the flood impact and risk assessment that accompanies your DA
• Setting floor levels, driveway levels and access grades that satisfy the flood planning level
• Designing stormwater drainage that works with, not against, the flood regime – on-site detention, overland flow paths and discharge arrangements all interact with flood behaviour
• Responding to council requests for additional information, which on flood matters are common

Engaging the engineer early – ideally before purchase, and certainly before the architect fixes the design – avoids the all-too-common scenario where a completed design has to be lifted, re-planned or abandoned because the flood constraints were never properly scoped.

The practical takeaways

• The 2022 floods and the subsequent Independent Flood Inquiry drove real change in NSW flood planning – this is not business as usual.
• The Flood Risk Management Manual (2023) has replaced the 2005 manual, and the planning regulation now points to it, including the definitions of flood planning area and probable maximum flood.
• Councils are looking beyond the 1% AEP event, considering risk up to the PMF for emergency response and vulnerable land uses.
• Flood-affected DAs need proper flood impact and risk assessments, compliant floor levels, justified filling and credible evacuation arrangements.
• Due diligence before buying flood-affected land – planning certificate, council flood information, engineering advice – is the cheapest insurance you will ever buy.

Frequently asked questions

How do I find out if my land is flood-prone?

Start with the section 10.7 planning certificate, which flags flood-related development controls, then request the council’s adopted flood levels and mapping for the property. If the picture is unclear or the stakes are high, have a civil engineer review the available flood studies and advise on what the constraints mean for your plans.

Can I still build on flood-prone land in NSW?

In many cases, yes. Flood-prone does not automatically mean unbuildable – it means the development must be designed to manage the risk. That usually involves meeting the flood planning level for floor levels, avoiding adverse impacts on flood behaviour, and demonstrating safe evacuation or refuge. High-hazard floodways and vulnerable land uses face much tighter restrictions.

What replaced the 2005 Floodplain Development Manual?

The NSW Flood Risk Management Manual, gazetted in June 2023, together with its toolkit of supporting guidelines on flood modelling, floodplain categorisation, risk and emergency management, and land use planning. The Environmental Planning and Assessment Amendment (Flood Planning) Regulation 2023 updated the statutory references, including Schedule 9 of the EP&A Regulation, to point to the new manual.

Do I need a flood report for my DA?

If the council identifies your site as flood-affected, almost certainly. The scope varies – from a concise assessment against council’s adopted flood levels through to detailed hydraulic modelling – depending on the site, the proposal and the quality of existing flood information. Your civil engineer can confirm the scope with council before you spend money on the wrong level of study.

Need help with a flood-affected site?

Contrive Consultants is a civil and stormwater engineering consultancy based in Bella Vista, serving builders, developers and rural landowners across NSW, including regional areas via remote delivery. We prepare flood impact and risk assessments, stormwater designs and civil documentation that get DAs through council. Explore our civil and stormwater engineering services, call us on +61 497 848 111, email info@contriveconsultants.com.au, or get in touch for a site-specific chat before you buy or lodge.