Miguel G Cruz

The Commonwealth Scientific and Industrial Research Organisation | CSIRO · Environment

The knowledge of a free-burning fires potential rate of spread is critical for safe and effective bushfire control and use. A number of models for predicting the head-fire rate of spread in various types of Australian vegetation have been developed over the past 60 years or so since Alan G. McArthur began his pioneering research into bushfire behav...

Fireline intensity is the rate of energy or heat release per unit time per unit length of fire front (kW/m). Numerically, it is equal to the product of the fuel low heat of combustion (kJ/kg), quantity of fuel consumed in the flaming front (kg/m2), and the linear rate of fire spread (m/s).

Key message The collective analysis of a relatively large number of wildfire observations documented in conifer forests, dry eucalypt forests and temperate shrublands revealed that the forward rate of fire spread is roughly 10% of the average 10-m open wind speed, provided both are expressed in the same units (e.g. km h −1 ). Context Knowledge of...

Generalised statements about the state of fire science are often used to provide a simplified context for new work. This paper explores the validity of five frequently repeated statements regarding empirical and physical models for predicting wildland fire behaviour. For empirical models, these include statements that they: (1) work well over the r...

The knowledge of a free-burning fire’s potential rate of spread is critical to safe and effective bushfire control and use in Australia. A number of models for predicting the rate of fire spread in various Australian vegetation types have been developed over the past 60 years or so since Alan G. McArthur began his pioneering research into bushfire...

Background Wildfire propagation is inherently non-steady, although forecasts of their spread focus on a pseudo-steady state assumption. Aims To investigate the variability in rate of fire spread of wildfires in southern Australian grassland landscapes, and the effect of landscape features in inhibiting fire propagation. To evaluate the adequacy of...

Background. Assessment of fuel hazard has become the dominant method of describing Australian forest fuel complexes, despite a lack of evidence supporting the veracity of its underpinning assumptions. Aims. To analyse and discuss the merits of fuel hazard ratings and scores in representing measurable fuel characteristics, such as fuel load and fire...

Background In 1986, CSIRO conducted a large program of experimental fires in grassland at Annaburroo Station, Northern Territory, Australia, with the objective of quantifying the effect of fuel condition (load and height) on fire behaviour. Aims This paper provides the data collected during this program, representing a unique set of observations an...

In this comment we examine a recent study published in Environmental Research Letters that analysed fire history data from forests in Western Australia to suggest that changes in forest structure result in a long-term reduction of fire risk after 56 years since last fire. We examine the data underpinning this study and find that its strongly skewed...

Background Development of the Australian Fire Danger Rating System began in 2017 with a project aimed at demonstrating the feasibility of a new fire danger rating system through a Research Prototype (AFDRSRP) that accounted for variability in Australian vegetation types, was nationally applicable, modular and open to continuous improvement. Aims In...

Empirical fire models, designed for public messaging of fire danger, prescribed-burning decision making, resource management, and fire-spread-rate prediction, are often used in climate studies to investigate potential changes in recent and future wildfires and prescribed burning opportunities. Prior studies have shown that some of these models are...

Background Crown fires are an ecologically necessary but hazardous process in conifer forests. Prediction of their behaviour in Canada has largely depended on the Canadian Forest Fire Behaviour Prediction System, in which fire weather indices drive primarily fixed fuel type models. The Crown Fire Initiation and Spread (CFIS) system presents a more...

Background: Fire behaviour simulation and prediction play a key role in supporting wildfire management and suppression activities. Aims: Using machine-learning methods, the aim of this study was to predict the onset of fire propagation (go vs no-go) and type of fire behaviour (surface vs crown fire) in southern Australian semiarid shrublands. Met...

Prediction of wildfire propagation plays a crucial role in reducing the impacts of such events. Various machine learning (ML) approaches, namely Support Vector Regression (SVR), Gaussian Process Regression (GPR), Regression Tree, and Neural Networks (NN), were used to understand their applicability in developing models to predict the rate of spread...

Wildland fires are among the most complicated environmental phenomena to model. Fire behavior models are commonly used to predict the direction and rate of spread of wildland fires based on fire history, fuel, and environmental conditions; however, more sophisticated computational fluid dynamic models are now being developed. This quantitative anal...

An analysis of a dataset (n = 58) of high-intensity wildfire observations in cured grasslands from southern Australia revealed a simple relationship suitable for quickly obtaining a first approximation of a fire's spread rate under low dead fuel moisture contents and strong wind speeds. It was found that the forward rate of fire spread is approxima...

The suggestion has been made within the wildland fire community that the rate of spread in the upper portion of the fire danger spectrum is largely independent of the physical fuel characteristics in certain forest ecosystem types. Our review and analysis of the relevant scientific literature on the subject suggests that fuel characteristics have a...

The ‘Balbi model’ is a simplified rate of fire spread model aimed at providing computationally fast and accurate simulations of fire propagation that can be used by fire managers under operational conditions. This model describes the steady-state spread rate of surface fires by accounting for both radiation and convection heat transfer processes. I...

Reliable and accurate models of the speed of a wildfire front as it moves across the landscape are essential for the timely prediction of its propagation, to devise suitable suppression strategies and enable effective public warnings. We used data from outdoor experimental fires and wildfires to derive an empirical model for the rate of fire spread...

O período entre 2018 e 2022 mostrou-nos que o problema dos incêndios à escala global não está a diminuir, antes pelo contrário. Parece que as consequências das alterações climáticas já estão a afectar a ocorrência de incêndios florestais em várias partes do Mundo, de uma forma que só esperaríamos que acontecesse vários anos mais tarde. Em muitos pa...

O período entre 2018 e 2022 mostrou-nos que o problema dos incêndios à escala global não está a diminuir, antes pelo contrário. Parece que as consequências das alterações climáticas já estão a afectar a ocorrência de incêndios florestais em várias partes do Mundo, de uma forma que só esperaríamos que acontecesse vários anos mais tarde. Em muitos pa...

This state-of-knowledge review examines some of the underlying assumptions and limitations associated with the inter-relationships among four widely used descriptors of surface fire behaviour and post-fire impacts in wildland fire science and management, namely Byram's fireline intensity, flame length, stem-bark char height and crown scorch height....

A 3-m between crown spacing is a commonly cited criterion found in the wildland-urban interface fire literature for minimizing the likelihood of a fully-developed crown fire from occurring in a conifer forest on level terrain. The validity of this general recommendation is examined here in light of our current state-of-knowledge regarding crown fir...

The prediction of wildfire rate of spread and growth under high wind speeds and dry fuel moisture conditions is key to taking proactive actions to warn and in turn protect communities. We used two datasets of wildfires spreading under critical fire weather conditions to evaluate an existing rule of thumb that equates the forward rate of fire spread...

A field-based experimental study was conducted in 50×50m square plots to investigate the behaviour of free-spreading fires in wheat to quantify the effect of crop condition (i.e. harvested, unharvested and harvested and baled) on the propagation rate of fires and their associated flame characteristics, and to evaluate the adequacy of existing opera...

A recent numerical simulation study by Moinuddin et al. (2018) determined that over a specific range of Froude numbers defined by them as ‘plume mode’, grass fuel height has a strong inverse effect on the rate of fire spread in grasslands. They then suggest that a relationship for effect of fuel height derived from their simulation results could be...

Sutherland et al. (2020) used simulations from a physics-based numerical fire behaviour model to investigate the effect of the ignition protocol (namely length, direction and rate of ignition) on the spread rates measured in experimental fires. They concluded that the methods used by Cruz et al. (2015) were inadequate as the fires were not spreadin...

Flame dimensions incorporate four important geometrical descriptors, namely, flame height (the average vertical extension of flames), flame depth (the width of continuous flaming behind the leading fire edge), flame length (the length of flames measured along the axis of the fire front from the midpoint of the flame depth to the flame height tip),...

Crown scorch height represents the vertical distance above the ground that lethal scorching of the needles or leaves in the canopy of a forest or shrubland ecosystem has occurred as a result of the heat generated from a surface fire.

This presentation describes a proposed scheme (in prep.) to link several empirical models using Canadian datasets for predicting fire spread in conifer forests based on stand structure.

Coarse woody debris (>0.6cm in diameter) is an important component of the fuel complex in Australian eucalypt forests, influencing both fire behaviour, smoke production and post-fire ecological processes. We investigated how physical characteristics of woody fuel affected ignition and consumption during an experimental fire where the fuel complex c...

Fire behaviour characteristics define the impacts on society and the environment. While wildland fire science has expanded to include the analysis of fire activity and effects across the globe, an understanding of global fire behaviour patterns and its drivers remains incomplete. We utilized the literature and unpublished datasets as sources for co...

The effect of grass fuel load on fire behaviour and fire danger has been a contentious issue for some time in Australia. Existing operational models have placed different emphases on the effect of fuel load on model outputs, which has created uncertainty in the operational assessment of fire potential and has led to end-user and public distrust in...

The prediction of fire propagation across landscapes is necessary for safe and effective fire management. We analyzed the predictive accuracy of models currently used operationally in Australia for predicting fire spread rates in five different fuel types (grasslands, temperate and semi-arid shrublands, dry eucalypt and conifer forests) compared to...

Coarse woody debris (.0.6 cm in diameter) is an important component of the fuel complex in Australian eucalypt forests, influencing both fire behaviour, smoke production and post-fire ecological processes. We investigated how physical characteristics of woody fuel affected ignition and consumption during an experimental fire where the fuel complex...

Appropriate categorisation and description of living vegetation and dead biomass is necessary to support the rising complexity of managing wildland fire and healthy ecosystems. We propose a hierarchical, physiognomy-based classification of wildland fire fuels—the Bushfire Fuel Classification—aimed at integrating the large diversity of Australian ve...

This paper represents our response to the questioning byMell et al. (2018)of our interpretation (Cruz et al. 2017) of five generalised statements or mantras commonly repeated in the wildland fire behaviour modelling literature. We provide further clarity on key subjects and objectively point out, using examples from relevant scientific findings, th...

Large plantations of radiata pine (Pinus radiata Don) are susceptible to widespread damage from wildfires that compromise the sustainability of forest production and downstream industries. Fuel management zones, strategically located plantation areas where an intensive silvicultural prescription comprising multiple prunings and thinnings aim to con...

Crown fires are complex, unstable phenomena dependent on feedback mechanisms between the combustion products of distinct fuel layers. We describe non-linear fire behaviour associated with crowning and the uncertainty they cause in fire behaviour predictions by running a semiphysical modelling system within a simple Monte Carlo simulation framework....

This state-of-knowledge review examines some of the underlying assumptions and limitations associated with the inter-relationships among four widely used descriptors of surface fire behaviour and post-fire impacts in wildland fire science and management, namely Byram's fireline intensity, flame length, stem-bark char height and crown scorch height....

The moisture content of dead grass fuels is an important input to grassland fire behaviour prediction models. We used standing dead grass moisture observations collected within a large latitudinal spectrum in Eastern Australia to evaluate the predictive capacity of six different fuel moisture prediction models. The best-performing models, which ran...

On the 17 March 2016, the Country Fire Authority of Victoria conducted a high intensity experimental fire to test the performance of three different vehicle/crew protection spraying systems. The vehicles tested were a Medium Tanker with a water spraying system (MT), an ultra light tanker with a Compressed Air Foam System (UL-1CAFS) and ultra light...

The National Wildfire Coordinating Group’s definition of extreme fire behavior indicates a level of fire behavior characteristics that ordinarily precludes methods of direct control action. One or more of the following is usually involved: high rate of spread, prolific crowning/spotting, presence of fire whirls, and strong convection column. Predic...

The capacity to predict fire dynamics in fuel beds comprised of live and dead fuel components is constrained by our limited understanding of the effects of live fuels on fire propagation. A field-based experimental burning program was conducted to specifically address the effect of the degree of curing, the proportion of dead fuels in the fuel bed,...

Understanding the potential behavior of a wildfire is critical to ensuring the safety of those people in its path, either fighting it or fleeing from it. This is especially critical when unexpected behavior occurs that can entrap firefighters in a life-threatening situation.

A shrubland fire behaviour dataset was assembled using data from experimental studies in Australia, New Zealand, Europe and South Africa. The dataset covers a wide range of heathlands and shrubland species associations and vegetation structures. Three models for rate of spread are developed using 2-m wind speed, a wind reduction factor, elevated de...

Quantification of fire-prone vegetation is a challenge for land and fire managers who need explicit fuel data to support fire management decision-making. Fuel characteristics including the distribution of fuel elements by size class, live and dead components, compactness, and horizontal and vertical continuity are important determinants of fire beh...

Grass senescence, or grassland curing, is a dynamic process in which grass fuels transition from a live to dead state and, in turn, influence fire dynamics. In the present study we examined the process of curing with specific consideration of changes in fuel structure that will affect potential fire behaviour. Our sampling protocol expanded the fue...

The relative variation in predicted fireline intensity and the wind speed thresholds for the onset of crowning and active crown fire spread in a lodgepole pine (Pinus contorta Dougl. ex Loud.) stand subjected to a commercial thinning operation were examined. This involved seven distinct scenarios, each with different assumptions regarding fine dead...

Tables have been constructed for use in making quick estimates of canopy base height, canopy fuel load, and canopy bulk density from visual observations or field measurements of stand height, basal area, and stand density for pure stands of ponderosa pine (Pinus ponderosa Dougl. ex Laws.), lodgepole pine (Pinus contorta Dougl. ex Loud.), and Dougla...