Three fuel models for predicting urban fire spread – a stopgap for emergency management in the US

Background: Prevailing American wildland fire modelling systems fail to predict fire growth in urban areas due to the absence of burnable urban fuels. Aims: This research aims to identify fuel models that optimise fire spread in urban areas relative to a hypothetical fire spread model derived from observations of recent urban fires. Methods: A target Rate of Spread (RoS) is derived from observations of seven urban conflagrations to anchor the model to absolute RoS. Exhaustive parameter sweeps are used to identify combinations of fuel variables that result in optimal performance. Key results: The target RoS is 0.81 km/h. Parameter sweeps converge on unique sets of fuel parameters including (1) BU0, an unconstrained custom fuel model; (2) BU1, a custom fuel model that operates within the constraints of current US modelling systems; and (3) Anderson Fuel Model 9, a best-performing standard fuel model. Conclusions & implications: Although this approach stretches current modelling systems beyond their intended design, the resultant fuel models provide a necessary stopgap for emergency management until urban-specific fire spread models find their way into operational use.