Massive short distance spotting has been suspected of increasing the forward rate of spread of bushfires since McArthur (1967) attributed a three-fold increase in rate of spread to short distance spotting at a fire in Daylesford. However, research into spotting has generally focussed on the prediction of long distance spotting, perhaps because of its more obvious effects on suppression of bushfires. The amount of spotting that a fire generates and the distance that spotfires start from the main fire is dependent on the amount and type of bark fuel present, as this is the primary source of embers. / Existing models of fire behaviour have proposed only one model that allows spotting to influence the forward rate of spread of the main fire - the formation of pseudo fire fronts. This thesis proposes two new inl1uence mechanisms; pre-frontal burnout and the "indraught effect". Three hypotheses have been formed to test these three influence mechanisms. / As it is difficult, costly and dangerous to use high intensity fires for experimental purposes, a fire simulation model (SAROS) was developed to run on a personal computer. The SAROS model is based on the McArthur fire behaviour model (1967), with the addition of mechanisms that allow spotting to affect the forward rate of spread of the main fire. SAROS has been tested against data from fires where spotting was thought to have significantly increased the forward rate of spread, and is shown to be a reasonable model of fire behaviour. / Further experiments were carried out to test the sensitivity of the model to the input variables and the impact of each of the variables in the model on changes in forward rate of spread due to spotting. The SAROS model shows that it is possible for massive short distance spotting to increase the forward rate of spread by over 300% of the McArthur predicted rate of spread. However under the conditions where McArthur reported spotting increasing the rate of spread by a factor of three, the SAROS model accounts fbI' only around two thirds of that increase.
| Identifer | oai:union.ndltd.org:ADTP/245734 |
| Creators | Macaulay, Andrew S. |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
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