Tis the season……for fire

a-firefighter-gives-water-to-a-koala-during-the-devastating-black-saturday-bushfires-that-burned-across-victoria-australia-in-2009-1345608759_b

(www.abc.net.au)

It’s that time of year again folks………the ladders are out, and the gutters are getting gutted.  Leaf litter is getting swept away, and sand breaks are being cleared. Chainsaw are being put away and local government staff are trimming your verge tree, that one getting too close to the power line.

This can only mean one thing: bushfire season is upon us!

Epicormic growth on the stems of trees (Eucalyptus spp.) is characteristic after being burnt (photo by Tibor Hegedis)

Bushfires are a naturally occurring phenomenon in Australia, most commonly occurring during the summer when temperatures are high and conditions are dry.  Lightning is the predominant natural cause and thought to behind about half of all ignitions in Oz.  Fire has been present in the Australian landscape for millions of years – long before the arrival of us humans – and as a result, has influenced the evolution of our native plants and animals. Aboriginal people have used fire for thousands of years to foster grasslands for hunting and to clear tracks through dense bush.

These days there are also quite a few ways in which we can accidentally cause fires ourselves, and too often with devastating consequences. This includes arcing from overhead power lines, accidental ignition from agricultural clearing, grinding and welding, campfires, cigarettes and dropped matches, machinery, and controlled burn escapes. Then there are those arsonists who deliberately start fires (we do not like them at all).

The basic factors which determine whether a bushfire will occur include the presence of fuel, oxygen and an ignition source. More specifically, fire intensity and the speed at which a bushfire spreads depends on temperature, fuel load, fuel moisture, wind speed and slope angle.

Areas with large fuel loads (i.e. dense forests and or grasses) are particularly susceptible, and generally speaking, the greater the fuel load, the hotter and more intense the fire. Some types of grasses burn very rapidly, while larger fuels, such as tree trunks, do not burn as easily. Many native plants have evolved a number of strategies to survive, require, or even encourage fire as a way to eliminate competition from less fire-tolerant species. e.g. the natural oil within Eucalypt trees promotes the combustion of fuel and shoots will sprout or seeds drop from trees after a fire.

Visual fuel load guide of the Swan Coastal Plain and Darling Scarp (left: light understorey & leaf litter, right: moderate to dense understorey of grass trees & native vegetation)

Visual fuel load guide of the Swan Coastal Plain and Darling Scarp (left: light understorey & leaf litter, right: moderate to dense understorey of grass trees & native vegetation)

And as we already know, long-term temperature trends linked to global warming are resulting in hotter, longer and more regular heat waves, and increasing the frequency and severity of bushfires which can turn into intense and destructive firestorms (the most tragic being the Black Saturday bushfires in Victoria in 2009 with 173 recorded deaths).

In response to these trends and in the shadow of fires in Perth and the southwest region in 2011, the Office of Bushfire Risk Management was set up in early 2012 as part of the WA Government’s response to the findings of the Keelty Report ‘Appreciating the Risk’. The role of the Office is to overseeing prescribed burning and bushfire related risk management in Western Australia and aims to ensure that organisations responsible for reducing bushfire related risk align their practices and procedures to Australian Standard ISO 31000:2009 Risk management – Principles and guidelines.

The WA Government has also been very busy in updating its bushfire risk related legislation and associated publications: the Planning and Development (Bushfire Risk Management) Regulations 2014 (draft) and Planning for Bushfire Protection Guidelines 2015 (draft revised). Together with the new draft State Planning Policy 3.7: Planning for Bushfire Risk Management (SPP 3.7) and the development of a Map of Bushfire Prone Areas, these instruments have been prepared with the purpose of assisting in the reduction of bushfire risk and impact on people, property and infrastructure through strategic planning, subdivision, development and other planning decisions proposed in bushfire-prone areas.

Bushfire hazard level assessments are now required by the Western Australian Planning Commission before a planning proposal or development application can be considered in order to understand the extent of the bushfire risk affecting the associated land. A bushfire hazard level assessment provides a “broad-brush” means of determining the likely intensity of a bushfire for a particular area by categorising and mapping land as having a low, moderate or extreme bushfire hazard level. Different hazard levels may be assigned to different parts of a property or, in the case of subdivision proposals, parts of individual lots. This assessment can then assist in informing the suitability of land for future subdivision and development, and help to determine suitable locations for particular land uses and development, including building envelopes. They are now expected to be included as part of the preparation of all levels of planning proposals from regional planning schemes and amendments all the way down to subdivision and development applications.

A more detailed Bushfire Attack Level (BAL) assessment is usually undertaken after a bushfire hazard level assessment has been conducted and provides a detailed assessment of risk. Bushfire protection criteria (a performance-based system of assessing bushfire management measures) are assessed against any proposal for a site with a moderate bushfire hazard level.  Bushfore Management Plans are site specific documents and summarise all this information and identify the extent of bushfire risk areas. They will provide further detail on site specific bushfire safety requirements such as hazard separation zones, firebreak access, fire fighting water supply, access and easements, and ongoing maintenance responsibilities.

fire danger warningsHowever where there is bushfire risk, there is also biodiverse plant and wildlife! And many new developments are also required to revegetate areas identified as parks and open spaces. How to manage this seeming conflict so that our communities stay safe in the case of fire without bull-dozing the native bushland which makes so much of Australia so special? Luckily this has been considered in the latest version of the Planning for Bushfire Protection Guidelines and strategies such as modifying buildings, lot yields and even in some cases structure plans to safely accommodate required revegetation are being accepted.

Essential Environmental is gaining expertise in the preparation of Bushfire Management Plans in consideration of such issues under the new sets of regulations and guidelines, and we are well on our way on having a couple of accredited Level 1 Bushfire Attack Level Assessors in the office! Shelley has been kept busy recently visiting sites in the Shire of Serpentine-Jarrahdale and the City of Swan as part of recent work undertaking Bushfire Attack Level assessments as part of proposed subdivisions. If you would like any further information regarding bushfire risk assessment, please contact our office!

For the latest alerts and warnings, please visit the Department of Fire and Emergency Services website:

http://www.dfes.wa.gov.au/alerts/Pages/default.aspx

To find out more about how to prepare yourself and your property in the case of a bushfire, please visit the Government of WA’s website:

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