In Australia there are several fire danger rating systems which are used by the various State and private land management agencies and the coordinating rural fire authorities. The most widely used are the McArthur Forest and Grassland Fire Danger Rating Systems which were devised by Alan McArthur in the early 1960’s. These rating systems have proven to be particularly useful and robust management tools and provide a good guidelines to the difficulty to suppression in either forest or grassland fuel types. The McArthur Fire Danger Rating Systems have been adopted by several countries with a fire climate similar to Australia.
Research in the last 10 years has shown there are certain deficiencies in the McArthur systems when they are used to predict fire behaviour and fire spread over the full range of fire weather conditions likely to occur in Australia. These deficiencies together with a number of ad-hoc changes prompted the need to review rating systems in use in Australia, particularly considering that with the increasing advent of geographic information systems (GIS) the ability to predict fire spread in specific fuel types is now becoming much more feasible than in the past. Also there has been a tendency to adopt some overseas fire behaviour models with an uncertain research basis and which have not been validated in Australia for use with computer models in conjunction with GIS data bases. As a result the Australian Forestry Council (AFC) sponsored a conference on Bushfire Modelling and Fire Danger Rating Systems which was held in Canberra on 11-12 July 1988 (see announcement of the release of the conference proceedings under “Recent Publications”). One of the resolutions oft his conference was that a national fire danger rating system be developed with the aim of standardising fire danger rating between States and to ensure that both the public and fire mangers develop a common understanding of fire danger. The AFC Research Working Group 6 (fire management research) was asked to review the need and if necessary propose a frame work for the development of an Australian Fire Danger Rating System.
In Australia the term fire danger is widely accepted as reflecting the severity of weather conditions affecting fire behaviour in a standard fuel type. Other factors included in the text book such as definition of fire danger, risk of ignition, and potential for damage are, in Australia, generally examined independently. Therefore the group recommended that for the purpose of public warnings a relatively simple system which predicts a burning index in grasslands is most appropriate and that this system retain the original relative scale established by McArthur which defined classes of suppression difficulty. The group concluded that Australia wide fire danger ratings were required for only three distinct fuel types: open grasslands, dry eucalyptus forests and heath/shrublands, and that forecasts for fire danger rating should be kept separate from predictions of fire spread and fire behaviour in specific fuel types. Systems for predicting fire behaviour should be designed to meet local needs and these predictions will require more accurate definition of fuel structures, fuel moisture regimes, local wind patterns and terrain than can be provided for general forecasts.
Thus the likely developments in Australia will be: the use of a uniform simple system of rating fire danger for use in public warning, setting general preparedness standards and fire tower duties; and, the use of well researched fire behaviour models combined in with geographic information systems to predict more accurately fire spread behaviour and through specific vegetation types over measured terrain.
From: Phil Cheney Address: CSIRO Division of Forestry P.O.Box 4008 Queen Victoria Terrace AUS-Canberra, ACT 2600