Builders and developers
Your development consent asks for a flood barrier.
Many builders first hear of a flood barrier when one appears in the conditions of consent. Here is what the barrier has to do, and what is needed before the certificates.
The requirement
What a flood barrier condition usually asks for.
Every consent is written for its own site, and yours governs. These are the parts to plan for.
- A level the barrier has to reachThe condition gives a flood planning level in metres AHD and sets the top of the barrier to it. The barrier height is that level less the finished surface level where the barrier sits.
- How the barrier operatesA condition for an automatic flood barrier, automatic flood gate or self-closing flood barrier means it has to close the opening without anyone activating it. Where it also has to work without an electricity supply, a self-operating barrier raised by the floodwater is the type that fits.
- Details before the construction certificateThe barrier's details go to the council or certifier with the construction certificate drawings, usually as part of a flood risk management plan. Have the technical specification and the operation and maintenance manual ready at this stage.
- Sign-off before the occupation certificateYour engineer certifies the works as built, including the mechanical flood barrier itself. Allow for a permanent plaque beside the barrier explaining its purpose and operation, and for a positive covenant on the title that makes the owners responsible for maintaining it.
- Operation and maintenance afterwardsThe barrier's operation and maintenance is often written into the building's flood emergency response plan, with the owners required to keep it in working order.
The product
How an automatic barrier closes the opening with no power.
A self-activating flood barrier, also sold as a passive or tilting flood barrier, lies flat in the driveway. Floodwater flows in beneath the panel, buoyancy lifts the panel upright, and it lowers under its own weight as the water recedes. Nothing is switched on and nobody has to be on site.
1. Standby. The barrier lies flush with the driveway. Cars and pedestrians cross it as normal. 
2. Flood arrives. Rising floodwater flows through the inlet into the recess beneath the panel. 
3. Rises automatically. Buoyancy lifts the panel into its upright position and closes the opening. 
4. Resets itself. As the water recedes, the panel lowers under its own weight back to flush.
These are the four stages of the Hydrodynamic Passive Flood Barrier, shown in section.
Scope of supply
What Flood Control supplies against the condition.
| What the condition needs | What we supply |
|---|---|
| A barrier that deploys with no power and no operator | The Hydrodynamic Passive Flood Barrier is raised by the floodwater itself and lowers under its own weight as the water recedes. |
| Top of barrier at the flood planning level | Made to the measured opening in a height of 0.6 m, 0.8 m, 1.0 m or 1.2 m. 1.2 m is the tallest we make. |
| A vehicle entry that stays in use | Recessed flush with the slab and trafficable to 20 tonnes GVM to AS 1170.1 when fully lowered. |
| An existing building where a recess cannot be cut | A surface-mounted version fixed onto the slab, with a ramp supplied for each side so vehicles drive over the lowered panel. |
| Barrier details for the construction certificate | Shop drawings for the opening, showing the recess the builder has to form in the slab. |
| Operation and maintenance manual | Supplied with the barrier. |
| Engineer's certification, plaque and covenant | These sit with your engineer, certifier and solicitor. Flood Control supplies the product and its documents and does not install or certify. |
Where the site has dependable power and wants remote control, the Automatic Flood Barrier System is the powered alternative. The apartment building project shows two passive barriers supplied for a lobby entry and a car park entry.
FAQ
Flood barrier condition FAQs.
What is a mechanical flood barrier?
A mechanical flood barrier, or mechanical flood gate, is a barrier that moves to close an opening, such as a panel that rises across a basement car park entry. A raised driveway crest or a bund wall is a fixed measure, not a mechanical one.
Is an automatic flood barrier the same as a self-closing flood barrier?
Both describe a barrier that deploys without a person activating it. An automatic barrier can be powered, raised by a hydraulic pump on water-level sensing, or passive, raised by the floodwater itself. Where the barrier must not need electricity or human operation, only the passive type fits.
How high does the flood barrier need to be?
The consent states a flood planning level in metres AHD and requires the top of the barrier to reach it. The barrier height is that level less the finished surface level at the barrier. Both numbers are usually on the approved drawings and in the flood report lodged with the application.
When does the barrier have to be chosen?
Before the construction certificate drawings are finished. On a new build the barrier sits flush in a recess formed in the slab, so the slab cannot be poured until the barrier is selected. The Hydrodynamic Passive Flood Barrier has a lead time of 70 to 90 days.
Does Flood Control install the barrier?
No. Flood Control supplies the barrier with shop drawings, an installation guide and an operation and maintenance manual, and gives remote technical support. Your builder or contractor installs it.
Send us the condition and the opening width.
With the condition wording, the flood planning level and the width of the opening, we can quote a barrier made for that opening.
Request a Quote