Siting for Bushfire Defence.

Siting for Bushfire Defence: Strategies for Achieving and Maintaining Bushfire Resilience

Site Selection and Layout

Siting a dwelling for bushfire defence goes beyond merely choosing a plot of land; it requires strategic planning in terms of layout, geology, vegetation, proximity to other structures or boundaries and many other factors.

The primary objective is to minimize the impact of a bushfire on your property through careful site selection and layout planning.

The key to a resilient site layout is maximizing the defensive capabilities of natural and artificial barriers such as slope, vegetation management, and backing these up with non-combustible landscaping features.

Choosing a site on the leeward side of hills, or with a natural windbreak, may not reduce the overall bushfire risk but avoiding steep slopes can be crucial as fire travels more quickly uphill.

Moreover, from a design perspective, the site layout should allow convenient positioning of structures to create ease of evacuation, defensible spaces that make bushfire fighting easier. Always consider if the placement of your dwelling allows easy access for firefighting and evacuation efforts.

Suitable Boundary Setbacks

Establishing suitable setbacks from property boundaries is essential to mitigating fire risks. The greater the distance between your home and the boundary, the better your chances of minimizing the impact of radiant heat and flying embers.

Regulations often require specific boundary setbacks, depending on the land size and local bushfire risk level. For example, the Shire of Mundaring mandates that the Asset Protection Zone (APZ) surrounding any habitable building be a minimum of 20 meters from all building structures, this is not always the right distance, its a great start but this number will be site specific.

Having a significant boundary setback increases the defensible space around your dwelling, providing more area to fight fires and reducing the likelihood of bushfire flames reaching the home. As part of your overall bushfire protection plan, boundary setbacks should be carefully considered early on in the process by allowing a BPAD Accredited practitioner to prescribe these.

Asset Protection Zone (APZ) Size

An Asset Protection Zone (APZ) serves as a buffer zone around dwellings to minimize bushfire risks through reduced vegetation fuel loads.

The ideal APZ minimizes the amount of flammable material around a property, thereby reducing the intensity of any approaching fires and enhancing the defence capabilities of the site.

The APZ size varies depending on local regulations and specific site conditions. Generally, maintain a 20-meter APZ as the standard with low fuel loads, typically 2 tonnes per hectare or lower, by regularly clearing dead vegetation and keeping the grass short the APZ will significantly reduce the risk.

APZs should also include non-combustible materials like gravel, pavements, and concrete paths, which act as firebreaks, adding further protection to your property.

For sloped lands, increasing the APZ by 1 meter for every degree of downslope is the basic method to accommodate the behaviour of downwind fires, however a Bushfire Consultant will be able to prescribe you a site specific APZ, without this it may not be suitable.

Defensible Space

The concept of defensible space involves creating a buffer between structures and natural vegetation and maintaining accessibility for firefighting efforts. A defensible space reduces fire intensity and the possibility of direct flame contact with buildings.

Property owners should integrate multiple defensible spaces, especially in areas prone to high bushfire risk. Some strategies to establish these spaces include:

1. Clearance: Regular clearance of dead vegetation, leaves, and other combustible materials within the APZ.
2. Non-Flammable Zones: Integrating non-flammable landscaping elements like stone paths, patios, and water features near structures.
3. Separation: Ensuring vegetation layers (understory, midstory, canopy) are separated horizontally and vertically to prevent fire ladders.
4. Accessibility: Designing spaces accessible to vehicles for firefighting and evacuation purposes.

By implementing these principles, you increase the survivability of structures and provide safe zones for firefighting activities.

Access

Ease of access to and from the property is a critical factor in bushfire defence. A well-thought-out access plan ensures quick evacuation and allows emergency services to reach and protect your property effectively.

Access considerations should include:

1. Driveways: Ensuring driveways are clear of dense vegetation and wide enough to accommodate fire trucks, with dual vehicle width or passing bays.
2. Entry Points: Having multiple entry and exit points can be lifesaving, especially if one path becomes blocked by fire or debris or by having the entrance close to the dwelling site. Your site should also be as close as practical to the road.
3. Clearance: Providing vertical and horizontal clearances along driveways to allow firefighting equipment and vehicles to pass through easily, in some cases on long driveways the ability for vehicles to pass each other.
4. Turnarounds: Sufficient space for vehicles to turn around near the dwelling avoids the need for reverse or awkward driving under emergency conditions or when visibility is reduced by smoke.
5. Access to fire water supply for the responding fire appliances to have the appropriate size water supply close to the dwelling and turn around area. This is usually a 10kL dedicated fire water supply with a 50mm male Camlock coupling.

Property owners can also consider neighbouring properties’ access, ensuring that evacuation paths are open and that alternative escape routes are part of the planning if suitable.

Vegetation and Other Hazards

Effective vegetation management significantly reduces bushfire risks. All vegetation should be assessed for its flammability, placement, and how it might contribute to the spread of fire. Assessing the vegetation gets completed for the site before any modification occurs, this ensures accuracy.

1. Low-Flammability Plants: Choose fire-resistant plants, such as succulents or low-flammability native species, to reduce fire spread a great guide is available from DFES Fire wise-Gardening-in-Western-Australia below.
2. Regular Maintenance: Include regular pruning, especially within the APZ. Remove dead materials and ensure trees and shrubs are under-pruned to prevent fire ladders .
3. Clear Separations: Maintain clear separations between tree crowns to prevent the easy spread of fire across canopies, this also controls the ground fuels over time.
4. Proximity to Structures: No trees or shrubs should be within 3 meters of habitable buildings, and branches must not overhang any structures. But the best case may be a much greater distance of 10 metres or more.

Be mindful of other hazards like wood heaps, gas cylinders, and flammable materials, and store them at a safe distance from the dwelling.

Install pathways and non-flammable surfaces adjacent to buildings to act as immediate barriers to fire spread.

Water, Electrical, and Gas

Siting for bushfire defence your reliable and defendable utilities can significantly improve your property’s bushfire resilience.

1. Water Storage: Non-combustible water tanks (e.g., made from concrete or corrugated iron) located in an appropriate area provides an additional water source during a bushfire .
2. Electrical Lines: Overhead electrical infrastructure is vulnerable to bushfires. Maintain clear vegetation around power lines on your property, and promptly report any irregularities in the area.
3. Gas Installations: Install gas tanks and lines with appropriate clearances from the house, on stable ground, away from flammable materials and point the valve away from flammable items.

Ensure that water, electrical, and gas installations are bushfire-ready to maintain essential services during a fire and support firefighting efforts.

Ease of Ongoing Maintenance/Management

Maintaining bushfire defences is an ongoing endeavour, requiring regular review and timely action to encapsulate the dynamic nature of bushfire risks.

Routine Procedures:

1. Vegetation Management: Regularly prune, clear dead plants, and maintain fuel loads, especially before peak bushfire seasons.
2. Equipment and layout Checks: Ensuring all fire-fighting and utility equipment, such as water pumps and hoses, are in working condition. Ensure open access and maintain defensible spaces effectively.
3. Structural Integrity: Regular inspection and maintenance of structures, focusing on sealing gaps, maintaining surfaces, and ensuring the structural integrity of eaves, windows, and roofs. You can view our retrofit guide here.

Planning Adjustments:

1. Monitoring Changes: Changes in vegetation around the property and how they impact bushfire risks need consistent monitoring and management. This includes understanding how growth over time in surrounding vegetation might alter bushfire risks.
2. Response Preparedness: Drills and training on bushfire response for all occupants increase immediate response capabilities during an actual event. This includes keeping up to date with Emergency WA, or DFES Website.

Engaging professional services for regular site assessments might also be beneficial. These professionals often have the expertise to recommend necessary interventions timely and effectively.

Conclusion

Siting a proposed dwelling with bushfire defence in mind involves a comprehensive approach that integrates planning, structural decisions, and ongoing management.

By carefully contemplating site selection, boundary setbacks, APZ size, defensible spaces, access routes, and proactive hazard management, you enhance the bushfire resilience of your property.