Short answer: a flood level survey in Geelong measures the ground and floor levels on your property in metres AHD (Australian Height Datum), the same height system that council and the catchment management authority use for flood levels. If your land is in a flood overlay or is otherwise liable to flooding, that survey lets the authorities compare your site with the applicable flood level and set or check a safe floor level for new buildings and extensions. You usually need it before you lodge planning or building plans, so it pays to order it early.
Low-lying land near the Barwon and Moorabool rivers, local creeks and the coast around Corio Bay and the Bellarine can carry flood controls. Many homeowners in suburbs like Belmont and Drysdale only find out when a designer or building surveyor asks for flood information. This guide explains what a flood level survey is, when you need one and how it fits into your approvals.
What is a flood level survey?
A flood level survey is a land survey that records accurate heights across a property and ties them to AHD. A licensed land surveyor connects the survey to a nearby permanent survey mark or benchmark so every level on the plan can be compared directly with the flood level issued by the authority.
A typical flood level survey shows:
- Natural surface levels across the site, often with contours
- Floor levels of the existing house, garage, sheds and other buildings
- Levels at the road, kerb, footpath and driveway crossover
- Drainage pits, swales and other features that affect how water moves
- Title boundaries and the position of existing buildings
- The applicable flood level, once the authority has provided it, so the gap between ground, floor and flood level is clear
It is closely related to a feature and level survey, and for many projects the two are done together in one site visit. You can see what we provide on our flood level surveys page.
When do you need a flood level survey in Geelong?
Your property has a flood overlay
Victorian planning schemes use three main flood overlays: the Floodway Overlay (FO), the Land Subject to Inundation Overlay (LSIO) and the Special Building Overlay (SBO), which covers stormwater flooding. A free planning property report from the Victorian Government’s planning website shows whether any of these apply to your land. If one does, buildings and works often need a planning permit, and the application will usually need survey levels in AHD.
Your land is liable to flooding, even without an overlay
Not all flood mapping has made it into planning schemes. Under regulation 153 of the Building Regulations 2018, the report and consent of the council is generally needed for a building permit on an allotment in an area liable to flooding. In that report, council can specify a minimum floor level. Before doing so it must consult the floodplain management authority, and the level must be at least 300 mm above the relevant flood level, unless the authority agrees to a lower floor. Some work, such as Class 10 buildings like garages and sheds, unenclosed floor areas and small alterations, is exempt from this regulation.
You are building, extending or subdividing
New houses, second dwellings, extensions, units and subdivisions on flood-affected land are the most common triggers. A flood level survey can also help when you are buying a property and want to understand the flood risk before you commit.
Who sets the flood level for Geelong properties?
For most of the Geelong region, the Corangamite Catchment Management Authority (CMA) is the floodplain management authority for riverine, waterway and coastal flooding, including land under the FO and LSIO. It provides property flood advice through a request form on its website. At the time of writing, Corangamite CMA says it does not charge for this advice, responds in writing within 28 days and does not give flood advice over the phone.
For stormwater flooding, including land in the SBO, the City of Greater Geelong assesses plans under an agreement with the CMA. Council’s published criteria say habitable floors must be at least 30 cm above the applicable flood level and non-habitable buildings such as garages and storage sheds at least 15 cm above. If your property is in the Surf Coast, Golden Plains, Colac Otway or Ballarat council areas, check with that council and the relevant CMA, as the process can differ.
Either way, the authority gives you a flood level in metres AHD. A flood level survey is what turns that number into something you can design and build to.
How a flood level survey fits into your project
1. Check your overlays and title
Download a planning property report and your certificate of title. Note any flood overlays, easements or covenants.
2. Book the survey early
We survey the site and connect it to AHD. Doing this before design means your architect or draftsperson knows the real ground levels and how far floors need to be raised.
3. Request flood advice
Apply to the CMA or council for the applicable flood level. Supplying a survey plan with AHD levels helps the authority understand your site and can save back-and-forth.
4. Design to the required floor level
Your designer sets the finished floor level using the authority’s advice. This can affect slab heights, steps, ramps, driveway grades and overall building height, so it is better to know early.
5. Set out and check levels during construction
Once a permit is issued, the floor level has to be built correctly. A building set-out marks the building position and a reference height on site, and we can check the finished floor level after the slab is poured if your builder, building surveyor or council asks for confirmation. Our guide to building set-out surveys in Geelong explains that stage in more detail.
Common mistakes to avoid
- Using an old or assumed datum. Levels on an arbitrary site datum cannot be compared with a flood level. Make sure the survey is in AHD.
- Waiting until the design is finished. Discovering that floors must sit higher can mean redesigning steps, access and height late in the process.
- Forgetting outbuildings and access. Garages, sheds and driveway access can also be assessed, so include them in the survey.
- Assuming no overlay means no flood risk. Some flood-prone land has not been mapped in the planning scheme yet, so check with the CMA and council.
Flood level surveys across Geelong and the region
Geelong Land Surveyors is a team of licensed land surveyors working across Geelong, Belmont, Drysdale and the Bellarine, the Surf Coast and Ballarat. We prepare flood level surveys that councils, CMAs, designers and building surveyors can use straight away.
Need a flood level survey? Request a quote online or call us on 0412 722 261 with your property address and what you are planning to build.
Flood level survey FAQs
How do I know if my Geelong property is flood affected?
Start with a free planning property report, which shows any Floodway Overlay, Land Subject to Inundation Overlay or Special Building Overlay. Because some flood mapping is not yet in planning schemes, you can also request property flood advice from Corangamite CMA or ask council.
What does AHD mean on a survey plan?
AHD stands for Australian Height Datum, the national height system used across Australia. Flood levels and survey levels are both given in metres AHD, so they can be compared directly.
How high above the flood level does my floor need to be?
It depends on the authority’s advice for your site. Under the Building Regulations 2018, a floor level specified by council must be at least 300 mm above the relevant flood level unless the floodplain management authority agrees to a lower level. For stormwater flooding, the City of Greater Geelong’s criteria are 30 cm for habitable floors and 15 cm for non-habitable buildings.
Is a flood level survey the same as a feature and level survey?
They overlap. A feature and level survey records site features and heights for design. A flood level survey focuses on levels in AHD that can be compared with the flood level, including existing floor levels. Often both are done in one visit.