Modelagem matemática e avaliação do comportamento do fogo em liteira de eucalipto

Abstract

Forest fires are natural disasters where the fire spreads uncontrollably about any type of vegetation. Besides being responsible for biodiversity reduction, forest fires generate huge economic losses in the forestry sector. The first studies modeling forest fire behavior were done in the first half of the twentieth century and were aimed to characterize fire behavior and assist in the prevention and combat operations. Although, since then, several models have been created, until now, there was no specific model for estimating fire behavior in Brazilian's eucalypt plantations. Knowing that the characteristics of the vegetation and weather play an important rule in the way that the fires behave, this study aimed to characterize the fire behavior in eucalyptus litter in the study area and develop specific mathematical models to describe the propagation rate of spread, the flame length, the fuel consumption and the burn time, based on easily obtained variables. Furthermore, it was evaluated the efficiency of the BehavePlus 5.0 software in simulate the fire behavior. In order to meet the proposed objectives, the initial step was to characterize the eucalypt plantations. The area defined as a standard model was the north coast of Bahia, region that has the largest eucalyptus plantation area in all the northeast of Brazil. The characterization was done through destructive sampling, where the average values for the fuel load, fuel bed depth and fuel bed bulk density where set and used as basis for the 105 laboratory burns. All fuel and weather variables that could influence in the fire behavior were controlled and measured in the experiments. Based on the values of the dependent and independent variables, linear regression mathematical models using the forward stepwise procedure were created. Seven mathematical models were built, all they highly significant and with coefficient of determination ranging between 0.58 and 0.82. The respective models were used to build a software to simulate eucalyptus litter fire behavior: Eucalyptus Fire Safety System ®. When comparing the data of the rate of spread and flame length simulated by the models developed in this work and simulated in the BehavePlus software versus the experimental data obtained in laboratory, it was achieved a better statistical performance for the models created here. Because of the difference between the simulated data by the BehavePlus and the experimental data, which were quite underestimated, it is not advised the use of the BehavePlus in the study area.