A perennial challenge in the management of fire is to strike a balance between the relative costs of bushfire mitigation, and the related losses incurred by the community.
In bushfire prone parts of the world models of the threat posed under varying fire prevention and suppression regimes have been developing for some years. More recently, these models have sought to combine seasonal and geographic data with the available fire behaviour science and suppression capability information in a way that assists both operational and strategic decision making.
Known generically as ‘decision support tools’ these models can greatly assist bushfire management agencies in a range of tasks including:
- helping to better understand how a particular bushfire will behave;
- better prediction, several months in advance, of the likely level of agency resourcing that will be needed in the forthcoming fire season
- achieving a more strategic ‘balance’ over the longer term between resources allocated to the suppression of bushfires and the resources allocated to preparing the bush, the fire fighting and support agencies, and the wider community for the bushfire season.
Because bushfires can move across different landscapes at varying rates of spread under varying conditions, there are many factors to consider in quantifying risk.
A new model
Since the formation of the Bushfire Cooperative Research Centre in late 2003 work has been underway on the development of a bushfire risk management model that will enable fire and land managers to better understand how the various elements of ‘bushfire risk’ interact.
There are high expectations for this model, both within the fire and land management agencies and in sections of the wider community. Both the Australasian Fire Authorities Council and the Bushfire CRC are strongly supportive of this ambitious research project, seeing it as having the potential to take the management of bushfire in Australia to a new level of sophistication.
The Bushfire Risk Management Model, led by Dr Kevin Tolhurst at the University of Melbourne, aims to produce a single management support system for the managers of fires in eucalypt dominated ecosystems. It will enable fire and land managers to better understand how the various elements of bushfire risk management interact. When completed the model will provide both a better understanding of how a bushfire will behave and how it will allow better prediction of the likely level of agency resourcing that will be needed in the forthcoming summer.
The model will also aid the development of a more strategic ‘balance’, over the longer term, between resources allocated to the suppression of bushfires, and the resources allocated to preparing the bush, the fire fighting and support agencies, and the wider community for the bushfire season.
The model being developed includes a simulation program that is capable of showing the spread of fire across the landscape, under different weather and fire suppression scenarios.
The first phase of the project (mitigation) has seen the definition of the fire management business model and the development of a set of ‘business rules’ that indicate how decisions are made to meet management objectives. From these rules has come a mathematical definition of how these factors interact. This allows the testing of various expenditure scenarios against varying levels of risk.
The second phase of the project is developing a conceptual model to describe the likelihood of a fire with particular characteristics occurring in a particular space and time across the landscape. The resultant fire spread simulation model (known as Phoenix) contains components that are designed to describe the ignition and spread of fires across the landscape under particular management and weather scenarios.
This process provides the calculation of a probability of a damaging fire emerging. Such probabilities will be affected by different management strategies such as prevention, protection, response, recovery and ecological burning.
As part of this phase of the project, ‘fire occurrence modelling’ is analysing past fires (their annual, seasonal and diurnal patterns) and producing a model which describes the historical data. The model will allow managers to predict the likely occurrence of fires in terms of topography, vegetation type, proximity to roads or urban development and other factors. Managers will also be able to estimate the potential impact on fires of changes in access, level of urban or infrastructure development, public education, fuel management and other elements.
Phoenix has now reached the prototype stage and following a workshop of practitioners from 12 end-user organisations in October 2006, it was tested and evaluated during the summer fire season in southern Australia.
The final phase of this project, fire impact modelling (consequence) will define the potential impact of a fire. Economic values being calculated include that of houses, timber, water, scenic quality and public utility functions.
Social values calculated include human life, trauma, human health and community function. Environmental values include harm to local species and ecosystems, soil erosion, reduced water yield and quality, and atmospheric pollution.
Meanwhile, another Bushfire CRC project called Bushfire Spread Simulation and Modelling is developing a new type of bushfire spread simulator, using simulation and animation technology, to support a wide range of fire management activities, including risk analysis, prescribed burning, wildfire suppression and incident control training. This project is led by Professor George Milne at the University of Western Australia.
Much of this work is aimed at finding ways of reducing the level of bushfire risk for given levels of investment and resourcing by governments and the wider community. While much has been learnt over the last few decades, about the management of fire in eucalypt dominated ecosystems, and in grasslands, much remains to be understood.
The behaviour of bushfires under extreme conditions (dry fuels, low humidity, high temperatures and strong winds), the effects of certain types of atmospheric instability, the impact of climate change, and the behaviour of humans in emergency situations (both fire-fighters, and of affected residents) are just a few of the areas where much remains to be done.
(This article appeared in the Autumn 2007 issue of Fire Australia magazine)