Improving the scientific accuracy behind fire danger ratings

The new Australian Fire Danger Rating System was launched on 1 September 2022, delivering more reliable predictions about fire weather, based on improved science, information, and data.

WAYNE KINGTON and ALANA BEITZ

AFAC

With the introduction of the new Australian Fire Danger Rating System (AFDRS), Australia now has a nationally consistent and more accurate system to predict and communicate fire danger.

The AFDRS replaces the McArthurbased system, which relied on science that is more than 60 years old. New technology, data, and research have greatly improved our ability to accurately predict fire behaviour and the potential threat to the community. The new AFDRS harnesses the latest scientific understanding about weather, fuel, and how fire behaves in different types of vegetation to improve the reliability of fire danger forecasts. This strengthens the ability of those working in emergency services to be prepared, make decisions, and provide accurate advice to the community.

Fire behaviour models

Fire behaviour models are mathematical models, usually tailored to specific vegetation types, that describe the way fire moves and spreads through those vegetation types. Because vegetation types have different structural characteristics, fire moves in a different way through each. Therefore, each requires its own modelling. The AFDRS uses eight fire behaviour models, rather than the two used by the McArthur- based system of fire danger. The eight vegetation type models are: „ forest „ grassland „ savanna „ spinifex „ shrubland „ mallee heath „ buttongrass „ pine.

Each of these fire behaviour models includes modifications to expand their use to 22 national fuel types. Using these models and fuel types, AFDRS is able to more accurately account for the diversity of vegetation types across Australia and to produce better predictions.

Introducing the Fire Behaviour Index

The AFDRS levels have been simplified and optimised for use by the community. There are now four levels: Moderate (green), High (yellow), Extreme (orange) and Catastrophic (red).

For fire management professionals and practitioners, a new Fire Behaviour Index (FBI) has been introduced. The FBI scale runs from zero to 100 and beyond, with increasingly high values indicating increasingly dangerous fire behaviour and, therefore, fire danger risk. In order to support fire operations properly, the FBI is made up of step-up categories based on fire behaviour transitions, where an increase in category reflects changed operational implications for: „ prescribed burning „ suppression response „ potential impacts.

The FBI does not describe a single physical property. Instead, it is a highlevel concept that unites a range of potential fire behaviour characteristics predicted from models for particular vegetation types. These include: „ fire intensity „ flame height „ rate of spread „ spotting potential.

PHOTO: NSW RFS

Flexibility for the future

To ensure flexibility and accuracy moving forward, the AFDRS is designed to be continuously updatable so that the system can take advantage of improving science, data, and information into the future.

For example, following the Victorian Black Saturday bushfires in February 2009, changes were made to fire danger ratings including the introduction of a ‘Catastrophic’ (or ‘Code Red’) rating and changes to the indices for grassland areas. While these changes were successfully and rapidly implemented to address a need at the time, experience

has shown that the original system was manipulated beyond its original intent and that it required a comprehensive review and redevelopment.

The AFDRS was designed to allow it to be readily updated as research into fire behaviour and other information improved. This includes the development of prototype indices for bushfire impact, suppression likelihood, and ignition likelihood, which may become important additions to the system in the future.

Training to support the switch to the new system

At present, land and rural fire management professionals are likely accustomed to the McArthur-based system of fire danger and may use this to frame their understanding of how fire behaves in various ecosystems. Emergency responders should be aware that the same index number, rating name or colour when used by the AFDRS may now represent something different than they might be used to. AFAC has developed a suite of training assets to support the switch to the new system. The training assets include: „ eLearning courses—the quickest way to learn about the new system „ modular assets—teacher aids such as lesson plans, videos, and

PowerPoint presentations to support the development or delivery of

AFDRS training.

The AFDRS training is delivered in three levels: „ Course 1: Introduction to the

AFDRS—for staff of government agencies and key stakeholders such as volunteers, local government, and private industry groups „ Course 2: Applying the AFDRS— for fire and land management professionals, planners, command and operational staff, and anyone requiring an applied knowledge of the AFDRS „ BoM Courses: AFDRS theory— for fire behaviour analysts, meteorologists, and those requiring a technical understanding of the theory behind the AFDRS, including equations. This is a technical course for specialists.

The new AFDRS brings with it a range of useful products that support operational decision-making, including the FBI Quick Guides, the Fire Danger Viewer, new Bureau of Meteorology products, and new climate outlook products. These products are detailed in the training resources.

Each step-up category of the FBI represents a transition in fire behaviour, such as a significant change in potential fire spread, suppression difficulty, or the expected scale of impact to life and property.

The AFDRS uses eight standard fire behaviour models that include modifications to expand their use to 22 fuel types.

State boundaries AFDRS fuel type Forest Wet forest Pine Woodland Arid woodland Gamba Woody horticulture Rural Urban Spinifex Spinifex woodland Mallee-heath Chenopod shrubland Heath Wet heath Button grass Low wetlands Grass Pasture Crop Horticulture Non-combustible Built-up

Access the AFDRS Training via the AFAC website: www.afac.com.au/ initiative/afdrs/afdrs-training. For more information about the AFDRS, visit www.firedangerratings.com.au.