New house on a flood control lot in Fairfield: floor levels and no CDC

A new house on a flood control lot in Fairfield is assessed under clauses 5.21 (flood planning) and 5.22 (special flood considerations) of Fairfield Local Environmental Plan 2013 and the flood risk management chapter of the Fairfield City Wide Development Control Plan, which sets the flood planning level, the minimum habitable floor level, the limits on fill and the evacuation requirements for each flood hazard category. The complying development route under the Housing Code is generally closed on these lots because Part 1 of the Codes SEPP restricts complying development on a flood control lot unless council or a hydraulic engineer certifies that the part of the lot being built on is outside the floodway, flood storage and high hazard areas. For home owners along Prospect Creek, Orphan School Creek, Cabramatta Creek, Clear Paddock Creek and the Georges River floodplain at Lansvale, Canley Vale, Fairfield, Carramar and Villawood, this means a council DA with a flood assessment, floor levels set above the flood planning level and a design that lets water through rather than pushing it onto the neighbours.

Who this is for: home owners planning a knock-down rebuild or new house on a Fairfield lot flagged as flood affected on the section 10.7 certificate, who want to understand what council will require and why the CDC route usually does not apply.

What is a flood control lot and how do I know if I have one?

The Codes SEPP defines a flood control lot as a lot to which flood related development controls apply in respect of development for dwelling houses, dual occupancies, multi dwelling housing or residential flat buildings, and notes that this is a prescribed matter for a planning certificate. Fairfield City Council identifies the lots on its flood mapping and reports the status on the section 10.7(2) certificate under the flood related development controls item. If the certificate says yes, the lot is a flood control lot whether or not the house itself has ever gone under.

The council’s flood studies for the Georges River, Prospect Creek, Orphan School Creek, Cabramatta Creek and the smaller local catchments produce hazard mapping in categories (floodway, flood storage, flood fringe, low and high hazard) and the 1 per cent annual exceedance probability and probable maximum flood extents. The hazard category, rather than the bare fact of being flood affected, decides what can be built. A lot in the flood fringe with 200 millimetres of 1 per cent AEP depth across the rear yard is a very different proposition from a lot in a mapped floodway.

The common mistake is to rely on the vendor’s statement that the house has never flooded. The flood planning level is a design standard derived from modelled flood behaviour, and it applies regardless of local memory.

What does clause 5.21 of Fairfield LEP 2013 require?

Clause 5.21 is the standard flood planning clause inserted into every standard instrument LEP in 2021. Subclause (2) states that development consent must not be granted to development on land the consent authority considers to be within the flood planning area unless it is satisfied the development is compatible with the flood function and behaviour on the land, will not adversely affect flood behaviour in a way that results in detrimental increases in flood affectation of other development or properties, will not adversely affect safe occupation and efficient evacuation or exceed the capacity of evacuation routes, incorporates appropriate measures to manage risk to life, and will not adversely affect the environment or cause avoidable erosion, siltation, loss of riparian vegetation or bank instability.

Subclause (3) adds matters council must consider: the impact of projected climate change on flood behaviour, the design and scale of buildings, measures to minimise risk to life and ensure safe evacuation, and the potential to modify, relocate or remove buildings if the area is affected. Subclause (5) defines the flood planning area by reference to the Flood Risk Management Manual (2023) and adopts the Considering Flooding in Land Use Planning Guideline. For a house DA, this translates into a flood impact assessment, floor levels above the flood planning level, a demonstration that the building does not displace flood storage or block a flow path, and an evacuation statement.

Clause 5.22 (special flood considerations) applies to sensitive and hazardous development (boarding houses, child care, seniors housing and the like) on land between the flood planning area and the probable maximum flood, and to other development on land where council considers a flood may cause a particular risk to life and require evacuation. A single house is not sensitive development, but where the lot is cut off from evacuation routes at the probable maximum flood, council can apply clause 5.22(2)(b) and ask for the evacuation assessment.

What floor level and design will council require?

The Considering Flooding in Land Use Planning Guideline (July 2026) states that the typical freeboard for residential development flooded from waterways such as rivers and creeks is 0.5 metres above the defined flood event, and that councils set the flood planning area and flood planning level through the floodplain risk management process and apply them through their DCPs. Fairfield’s flood chapter follows that model: habitable floor levels at or above the flood planning level, with different requirements for garages, non-habitable areas and existing buildings, and with controls tied to the hazard category of the lot.

The design consequence in Fairfield’s flat floodplain suburbs is usually a raised floor. Where the flood planning level sits 600 to 900 millimetres above natural ground, a slab on compacted fill may be accepted in a flood fringe area if the fill is contained to the footprint and compensatory storage is provided, whereas in flood storage areas a suspended floor on piers that lets water pass beneath is the expected outcome. The flood chapter and the council’s flood engineers decide which; the SEE has to present the choice and the flood assessment has to justify it.

Why is complying development usually excluded on a flood control lot?

Part 1 of the Codes SEPP sets out the land on which complying development may not be carried out. For flood control lots, the Housing Code can only be used if the relevant council or a professional engineer specialising in hydraulic engineering certifies that the part of the lot on which the development is to be carried out is not in a floodway, a flood storage area or the other high hazard categories listed in the SEPP; the Considering Flooding guideline describes the same certification test and notes that the complying development clauses also impose minimum finished floor levels and flood compatible materials where the code does apply.

On most Fairfield flood control lots the certification cannot be given, because the lot is inside the mapped flood planning area or a storage area, and the certifier has no power to assess flood impact on the merits. The DA route under clause 5.21 is then the only pathway, and it is the right one, because the questions council asks (storage, flow paths, evacuation) are exactly the ones a certifier cannot answer. The common mistake is to spend money on a CDC design first and discover the exclusion at certifier stage.

What does the Fairfield City Wide DCP require?

Fairfield City Council adopted the Fairfield City Wide Development Control Plan 2024 in August 2024 to replace the City Wide DCP 2013; the council’s development control plans page lists the current version (Amendment 2). The DCP’s flood risk management chapter applies the flood planning level and the hazard categories to each development type, and its general residential chapters carry the setback, height, landscaping and parking controls that still apply on a flood control lot. Because the chapter numbering and some of the numeric controls changed between the 2013 and 2024 plans, confirm the current chapter and the flood planning level for your lot with council before the design is drawn; council issues flood level information for a lot on request.

At LEP level, clause 4.3 applies the Height of Buildings Map, which in Fairfield’s R2 areas is typically 9 metres; a raised floor eats into that height, and a two storey house on a lot with a 900 millimetre freeboard requirement can breach the 9 metre limit at the ridge. Where it does, a clause 4.6 request is needed, and the flood requirement is a legitimate environmental planning ground for it. Clause 4.4 applies the mapped floor space ratio, and clause 4.1A and the Lot Size for Dual Occupancy Development Map govern lots where a duplex rather than a single house is being considered.

How to prepare a house DA on a Fairfield flood control lot

1. Obtain a section 10.7(2) and (5) certificate and council’s flood level information for the lot: the 1 per cent AEP level, the flood planning level and the hazard category.
2. Commission a survey with levels in AHD across the lot and the street, including the kerb and the crown of the road, and the floor levels of adjoining houses.
3. Engage a flood or civil engineer to prepare a flood impact assessment addressing clause 5.21(2)(a) to (e): compatibility, flood storage, flow paths, evacuation and environmental effects, with a fill and compensatory storage calculation if any fill is proposed.
4. Set the habitable floor level at or above the flood planning level, then check the resulting building height against clause 4.3 and prepare a clause 4.6 request if the ridge exceeds the mapped height.
5. Design the substructure and the materials below the flood planning level to the DCP flood chapter and the NCC, and locate electrical services above the level.
6. Prepare the Statement of Environmental Effects with a clause 5.21 and 5.22 assessment, the DCP compliance table and an evacuation statement, and lodge with the flood assessment and stormwater plan.
7. Expect council’s floodplain engineer to review the assessment; respond to any request for information with revised levels or storage calculations rather than argument.

Definitions

Flood control lot

A lot to which flood related development controls apply for houses, dual occupancies, multi dwelling housing or residential flat buildings, as defined in the Codes SEPP and reported on a section 10.7 certificate.

Flood planning area

The land below the flood planning level, defined by reference to the Flood Risk Management Manual and adopted in clause 5.21(5) of Fairfield LEP 2013.

Flood planning level (FPL)

The flood level adopted for planning purposes, usually the 1 per cent AEP flood level plus a freeboard of about 0.5 metres for residential development, set by council through its floodplain risk management process.

Probable maximum flood (PMF)

The largest flood that could conceivably occur at a location, used to define the extent of flood prone land and to test evacuation under clause 5.22.

Floodway

The part of the floodplain where a significant discharge of water occurs during floods; development that obstructs a floodway is not supported.

Freeboard

The height added above a flood level to allow for uncertainty in modelling, wave action and local effects; the Considering Flooding guideline describes 0.5 metres as typical for residential development.

URBA prepares Statements of Environmental Effects and clause 4.6 requests for new houses and knock-down rebuilds on flood control lots across Fairfield and the Georges River floodplain, and coordinates the flood impact assessment with our civil engineering sister company Contrive Consultants. See our Statement of Environmental Effects service and our Fairfield town planning page, or request a fee proposal for your lot.