Modelling the Effect of Grassland Fuel Bed Structure on the Headfire Rate of Spread

The dry weight of biomass to be consumed by fire in the wildland - urban interface (WUI) plays an important role in the spread of fire inside the WUI. In this paper, we present a model of grassland fire spread based on fuel load. The herbaceous stratum is represented by a heterogeneous fuel layer, with characteristics close to the real one. Fire propagation is simulated by using a two-phase model. Thirteen fire experiments in eastern Australia were used to test the predictive capacity of the model. The rates of spread are on the whole relatively well predicted. Using the fuel layer model to simulate fire spread, we tested how fuel load affects fire behavior. The results show that the fire spread rate does not systematically decrease with the increasing of fuel load. However, there may be a critical fuel load for rapid rate of spread, below or above which the rate of spread decreases.