INVESTIGATING THE RELATIONSHIP BETWEEN HORIZONTAL FOREST STRUCTURE AND FIRE BEHAVIOR USING A PHYS... more INVESTIGATING THE RELATIONSHIP BETWEEN HORIZONTAL FOREST STRUCTURE AND FIRE BEHAVIOR USING A PHYSICS-BASED FIRE MODEL Silvicultural treatments are increasingly being implemented across the Western US in fire-prone forests as a way to simultaneously reduce fire hazard while also increasing horizontal structural heterogeneity (tree spatial patterns). However, it is poorly understood how fire behavior is impacted by treatment designs that incorporate tree clumping spatial configurations that mimic patterns found within the historic structural ranges of forests frequented by low to mixed severity fire. The Wildland Urban-Interface Fire Dynamics Simulator (WFDS), a physics-based fire behavior model, was used to better understand the effect that heterogeneous horizontal forest structure has on fire behavior. Fire behavior across seven treated ponderosa pine forests with different spatial patterns were simulated and compared to each other, and to an untreated scenario. All forest simulatio...
Hazardous fuel reduction treatments conducted both through prescribed fire and mechanical means a... more Hazardous fuel reduction treatments conducted both through prescribed fire and mechanical means are a critical part of the mitigation of wildland fire risk in the United States. The US Federal Government has spent an average of $500t million each year on fuel reduction, from 2002-2012 (Gorte 2011). At present, however, rigorous experimental measurement of the effectiveness of such efforts, as they impact wildfire intensity and spread rate, has been limited. The project presented here is aimed at addressing this knowledge gap by taking a combined experimental and numerical modeling approach to quantifying fuel treatment effectiveness in the New Jersey Pine Barrens. In particular, this project deals with prescribed fire as a fuel treatment, and it involves the observation and measurement of fire spread rate, fuel consumption, and environmental conditions during two experimental prescribed fires. Given measurements of the pre-fire fuel characteristics and the environmental conditions, ...
Post-fire remote sensing provides a promising tool for assessing building damage, destruction, an... more Post-fire remote sensing provides a promising tool for assessing building damage, destruction, and defensive actions from wildland fire. However, limited studies exist to guide image acquisitions. Consequently, we compare remotely piloted aircraft systems and satellite post-fire imagery to ground-based assessments from the 2017 California Tubbs Fire to classify building damage, destruction, and defensive actions in an intermix and interface community. We also geolocate defensive action information from active fire images, videos, and eyewitness accounts. We utilize both manual and object-based classification approaches. Both types of overhead imagery using manual classifications had high kappa statistics ranging from 0.81 to 0.96, indicating almost perfect agreement with ground-based assessments for primary building destruction (e.g., homes). Object-based classifications of destruction had kappa statistics ranging from 0.63 to 0.88 for primary buildings, indicating substantial agreement. Additionally, manual and object-based classifications identified many destroyed secondary buildings (e.g., sheds) missed by ground-based assessments. Occlusions due to canopy cover contribute to lower classification results in the intermix community. All imagery missed significant damage identified in the ground-based assessment. Remotely piloted aircraft systems imagery was superior to satellite imagery in identifying defensive action indicators. Nonetheless, all image types are valuable additions to ground-based assessments of damage, destruction, and defensive actions. Finally, we demonstrate the importance of accounting for defensive actions in assessing building response at wildland-urban interface fires.
Tree spatial patterns in dry coniferous forests of the western US, and analogous ecosystems globa... more Tree spatial patterns in dry coniferous forests of the western US, and analogous ecosystems globally, were historically aggregated, comprising a mixture of single trees and groups of trees. Modern forests, in contrast, are generally more homogeneous and overstocked than their historical counterparts. As these modern forests lack regular fire, pattern formation and maintenance is generally attributed to fire. Accordingly, fires in modern forests may not yield historically analogous patterns. However, direct observations on how selective tree mortality among pre-existing forest structure shapes tree spatial patterns is limited. In this study, we (1) simulated fires in historical and contemporary counterpart plots in a Sierra Nevadan mixed-conifer forest, (2) estimated tree mortality, and (3) examined tree spatial patterns of live trees before and after fire, and of fire-killed trees. Tree mortality in the historical period was clustered and density-dependent, because trees were aggregated and segregated by tree size before fire. Thus, fires maintained an aggregated distribution of tree groups. Tree mortality in the contemporary period was widespread, except for dispersed large trees, because most trees were a part of large, interconnected tree groups. Thus, post-fire tree patterns were more uniform and devoid of moderately sized tree groups. Post-fire tree patterns in the historical period, unlike the contemporary period, were within the historical range of variability identified for the western US. This divergence suggests that decades of forest dynamics without significant disturbances has altered the historical means of pyric pattern formation. Our results suggest that ecological silvicultural treatments, such as forest restoration thinnings, which emulate qualities of historical forests may facilitate the reintroduction of fire as a means to reinforce forest structural heterogeneity.
We compare the use of post-fire aerial imagery to ground-based assessment for identifying buildin... more We compare the use of post-fire aerial imagery to ground-based assessment for identifying building destruction and damage at the 2012 Colorado Waldo Canyon Fire. We also compare active-fire defensive actions identified via manual and automated post-fire image classification to defensive actions documented from ground-based assessments (witness discussions, vehicle logs and images). For building destruction, manual and automatic image classification compared favourably to ground-based assessment, with low errors of commission (0.0–0.4%) and omission (0–1.2%). For building damage, classifying imagery manually had significant errors of commission and omission (59.0% and 57.9%) because ground-based assessments missed roof damage and image classification excluded interior and side damage, indicating the need for both techniques. Classifying imagery automatically for indicators of active-fire water suppression on buildings has Kappa statistics indicating a substantial agreement with docum...
Abstract Structure of vegetation significantly influences its flammability and resulting fire spr... more Abstract Structure of vegetation significantly influences its flammability and resulting fire spread. Despite considerable amount of laboratory studies, experimental works carried out with full plant specimens, representative of field conditions, are still limited. Present study aims to collect meaningful experimental data on structure and flammability of shrub of rockrose and evaluate the predictions of a fire model (WFDS) against this dataset. Spatial distribution of fuel elements, sorted according to their characteristic thickness, was established from destructive measurements. 28 fire tests were conducted with full plants under a calorimeter. Foliar moisture content was in the range of 4–18% on dry basis. Radiant panels were used as source of ignition. Flammability was investigated using ignitability, sustainability, combustibility and consumability. Comparison to previous studies highlighted the necessity of standardization among test procedures. Principal component analysis revealed four flammability regimes depending on proportion of thin fuel elements within the crown, position of ignition and duration of preheating. Finally, combustion dynamics of a shrub was numerically investigated with WFDS. A bulk density model was developed from the characterization study and used as input data for the numerical code. Predicted HRR was in good agreement with experiments, although simulation results need improvement in initiation phase of burning.
Even though much has been learned about the effects of microgravity on material flammability, fla... more Even though much has been learned about the effects of microgravity on material flammability, flame spread, and suppressant effectiveness, uncertainties remain regarding some of the practical aspects of fire protection in spacecraft. The experiments and simulations underway in this project are aimed directly at testing, understanding and improving NASA's existing policies and practices toward fire safety in spacecraft and extraterrestrial habitats. Specifically, the objectives of this research are: 1) Determine systematically the conditions that will ignite onboard flammable materials upon passage of an initial premixed gas, firebrand, or aerosol flame over these materials; 2) Test the effect of firebrands and configuration spacing; and 3) Determine the effectiveness of the flow of CO2 extinguisher or other extinguishing agents. Experimental and computational investigations are planned to achieve each of the three objectives above. Even though progress has been made in all of th...
ABSTRACT The last 15 years have seen the development of wildland and wildland-urban interface fir... more ABSTRACT The last 15 years have seen the development of wildland and wildland-urban interface fire behavior models that make use of modern numerical methods in wind and combustion physics. Currently, these approaches are too computationally expensive for operational use and, as for any fire behavior model, require validation through comparison to full-scale measurements. However, these "physics-based" models have the potential of providing a more complete understanding of fire behavior over a wider range of environmental conditions than empirically based models. The promise of physics-based models is not to replace the use of simpler and faster models, but to provide a well founded understanding of their limitations and a means of improving them. An example of this is to use the physics-based wildland-urban interface fire dynamics simulator (WFDS) to develop and evaluate a simpler level set model of surface fire spread. A basic implementation of the level set model performs reasonably well but requires further evaluation when applied to scenarios that include heterogeneous fuels and the potential influence of fire induced winds.
The advancement of three-dimensional, time-dependent fire behaviour models is best supported by p... more The advancement of three-dimensional, time-dependent fire behaviour models is best supported by publicly available, co-located, synchronised, quality-assured measures of pre-fire, active fire and post-fire conditions (i.e. integrated datasets). Currently, there is a lack of such datasets. Consequently, we discuss essential components to produce integrated datasets: metadata, implementation of geospatial and temporal standards, data management plans, quality assurance project plans and data quality objectives. We present example data quality objectives and a data model for grassland experiments developed based on our experience integrating data from the 2014 Camp Swift Fire and the 2012 Prescribed Fire Combustion and Atmospheric Dynamics Research experiments.
Wildland fire and ecological researchers use empirical and semi-empirical modeling systems to ass... more Wildland fire and ecological researchers use empirical and semi-empirical modeling systems to assess fire behavior and danger. This technical note describes the firebehavioR package, a porting of two fire behavior modeling systems, Crown Fire Initiation and Spread and a Rothermel-based framework, to the R programming language. We also highlight supporting data objects and functions to predict inputs required for fire behavior estimation. Last, this package contains functions for fifteen indices to express fire danger using weather and/or fuels observations. Specific advantages of predicting fire behavior using R, a free-and-open-source programming language, include freedom to adapt calculations to suit users’ needs, transparency of source code, and reduction of workflow inefficiencies, thereby aiding in sophisticated fire behavior analyses.
To pursue the development and validation of coupled fire-atmosphere models, the wildland fire mod... more To pursue the development and validation of coupled fire-atmosphere models, the wildland fire modeling community needs validation data sets with scenarios where fire-induced winds influence fire front behavior, and with high temporal and spatial resolution. Helicopter-borne infrared thermal cameras have the potential to monitor landscape-scale wildland fires at a high resolution during experimental burns. To extract valuable information from those observations, three-step image processing is required: (a) Orthorectification to warp raw images on a fixed coordinate system grid, (b) segmentation to delineate the fire front location out of the orthorectified images, and (c) computation of fire behavior metrics such as the rate of spread from the time-evolving fire front location. This work is dedicated to the first orthorectification step, and presents a series of algorithms that are designed to process handheld helicopter-borne thermal images collected during savannah experimental bur...
INVESTIGATING THE RELATIONSHIP BETWEEN HORIZONTAL FOREST STRUCTURE AND FIRE BEHAVIOR USING A PHYS... more INVESTIGATING THE RELATIONSHIP BETWEEN HORIZONTAL FOREST STRUCTURE AND FIRE BEHAVIOR USING A PHYSICS-BASED FIRE MODEL Silvicultural treatments are increasingly being implemented across the Western US in fire-prone forests as a way to simultaneously reduce fire hazard while also increasing horizontal structural heterogeneity (tree spatial patterns). However, it is poorly understood how fire behavior is impacted by treatment designs that incorporate tree clumping spatial configurations that mimic patterns found within the historic structural ranges of forests frequented by low to mixed severity fire. The Wildland Urban-Interface Fire Dynamics Simulator (WFDS), a physics-based fire behavior model, was used to better understand the effect that heterogeneous horizontal forest structure has on fire behavior. Fire behavior across seven treated ponderosa pine forests with different spatial patterns were simulated and compared to each other, and to an untreated scenario. All forest simulatio...
Hazardous fuel reduction treatments conducted both through prescribed fire and mechanical means a... more Hazardous fuel reduction treatments conducted both through prescribed fire and mechanical means are a critical part of the mitigation of wildland fire risk in the United States. The US Federal Government has spent an average of $500t million each year on fuel reduction, from 2002-2012 (Gorte 2011). At present, however, rigorous experimental measurement of the effectiveness of such efforts, as they impact wildfire intensity and spread rate, has been limited. The project presented here is aimed at addressing this knowledge gap by taking a combined experimental and numerical modeling approach to quantifying fuel treatment effectiveness in the New Jersey Pine Barrens. In particular, this project deals with prescribed fire as a fuel treatment, and it involves the observation and measurement of fire spread rate, fuel consumption, and environmental conditions during two experimental prescribed fires. Given measurements of the pre-fire fuel characteristics and the environmental conditions, ...
Post-fire remote sensing provides a promising tool for assessing building damage, destruction, an... more Post-fire remote sensing provides a promising tool for assessing building damage, destruction, and defensive actions from wildland fire. However, limited studies exist to guide image acquisitions. Consequently, we compare remotely piloted aircraft systems and satellite post-fire imagery to ground-based assessments from the 2017 California Tubbs Fire to classify building damage, destruction, and defensive actions in an intermix and interface community. We also geolocate defensive action information from active fire images, videos, and eyewitness accounts. We utilize both manual and object-based classification approaches. Both types of overhead imagery using manual classifications had high kappa statistics ranging from 0.81 to 0.96, indicating almost perfect agreement with ground-based assessments for primary building destruction (e.g., homes). Object-based classifications of destruction had kappa statistics ranging from 0.63 to 0.88 for primary buildings, indicating substantial agreement. Additionally, manual and object-based classifications identified many destroyed secondary buildings (e.g., sheds) missed by ground-based assessments. Occlusions due to canopy cover contribute to lower classification results in the intermix community. All imagery missed significant damage identified in the ground-based assessment. Remotely piloted aircraft systems imagery was superior to satellite imagery in identifying defensive action indicators. Nonetheless, all image types are valuable additions to ground-based assessments of damage, destruction, and defensive actions. Finally, we demonstrate the importance of accounting for defensive actions in assessing building response at wildland-urban interface fires.
Tree spatial patterns in dry coniferous forests of the western US, and analogous ecosystems globa... more Tree spatial patterns in dry coniferous forests of the western US, and analogous ecosystems globally, were historically aggregated, comprising a mixture of single trees and groups of trees. Modern forests, in contrast, are generally more homogeneous and overstocked than their historical counterparts. As these modern forests lack regular fire, pattern formation and maintenance is generally attributed to fire. Accordingly, fires in modern forests may not yield historically analogous patterns. However, direct observations on how selective tree mortality among pre-existing forest structure shapes tree spatial patterns is limited. In this study, we (1) simulated fires in historical and contemporary counterpart plots in a Sierra Nevadan mixed-conifer forest, (2) estimated tree mortality, and (3) examined tree spatial patterns of live trees before and after fire, and of fire-killed trees. Tree mortality in the historical period was clustered and density-dependent, because trees were aggregated and segregated by tree size before fire. Thus, fires maintained an aggregated distribution of tree groups. Tree mortality in the contemporary period was widespread, except for dispersed large trees, because most trees were a part of large, interconnected tree groups. Thus, post-fire tree patterns were more uniform and devoid of moderately sized tree groups. Post-fire tree patterns in the historical period, unlike the contemporary period, were within the historical range of variability identified for the western US. This divergence suggests that decades of forest dynamics without significant disturbances has altered the historical means of pyric pattern formation. Our results suggest that ecological silvicultural treatments, such as forest restoration thinnings, which emulate qualities of historical forests may facilitate the reintroduction of fire as a means to reinforce forest structural heterogeneity.
We compare the use of post-fire aerial imagery to ground-based assessment for identifying buildin... more We compare the use of post-fire aerial imagery to ground-based assessment for identifying building destruction and damage at the 2012 Colorado Waldo Canyon Fire. We also compare active-fire defensive actions identified via manual and automated post-fire image classification to defensive actions documented from ground-based assessments (witness discussions, vehicle logs and images). For building destruction, manual and automatic image classification compared favourably to ground-based assessment, with low errors of commission (0.0–0.4%) and omission (0–1.2%). For building damage, classifying imagery manually had significant errors of commission and omission (59.0% and 57.9%) because ground-based assessments missed roof damage and image classification excluded interior and side damage, indicating the need for both techniques. Classifying imagery automatically for indicators of active-fire water suppression on buildings has Kappa statistics indicating a substantial agreement with docum...
Abstract Structure of vegetation significantly influences its flammability and resulting fire spr... more Abstract Structure of vegetation significantly influences its flammability and resulting fire spread. Despite considerable amount of laboratory studies, experimental works carried out with full plant specimens, representative of field conditions, are still limited. Present study aims to collect meaningful experimental data on structure and flammability of shrub of rockrose and evaluate the predictions of a fire model (WFDS) against this dataset. Spatial distribution of fuel elements, sorted according to their characteristic thickness, was established from destructive measurements. 28 fire tests were conducted with full plants under a calorimeter. Foliar moisture content was in the range of 4–18% on dry basis. Radiant panels were used as source of ignition. Flammability was investigated using ignitability, sustainability, combustibility and consumability. Comparison to previous studies highlighted the necessity of standardization among test procedures. Principal component analysis revealed four flammability regimes depending on proportion of thin fuel elements within the crown, position of ignition and duration of preheating. Finally, combustion dynamics of a shrub was numerically investigated with WFDS. A bulk density model was developed from the characterization study and used as input data for the numerical code. Predicted HRR was in good agreement with experiments, although simulation results need improvement in initiation phase of burning.
Even though much has been learned about the effects of microgravity on material flammability, fla... more Even though much has been learned about the effects of microgravity on material flammability, flame spread, and suppressant effectiveness, uncertainties remain regarding some of the practical aspects of fire protection in spacecraft. The experiments and simulations underway in this project are aimed directly at testing, understanding and improving NASA's existing policies and practices toward fire safety in spacecraft and extraterrestrial habitats. Specifically, the objectives of this research are: 1) Determine systematically the conditions that will ignite onboard flammable materials upon passage of an initial premixed gas, firebrand, or aerosol flame over these materials; 2) Test the effect of firebrands and configuration spacing; and 3) Determine the effectiveness of the flow of CO2 extinguisher or other extinguishing agents. Experimental and computational investigations are planned to achieve each of the three objectives above. Even though progress has been made in all of th...
ABSTRACT The last 15 years have seen the development of wildland and wildland-urban interface fir... more ABSTRACT The last 15 years have seen the development of wildland and wildland-urban interface fire behavior models that make use of modern numerical methods in wind and combustion physics. Currently, these approaches are too computationally expensive for operational use and, as for any fire behavior model, require validation through comparison to full-scale measurements. However, these "physics-based" models have the potential of providing a more complete understanding of fire behavior over a wider range of environmental conditions than empirically based models. The promise of physics-based models is not to replace the use of simpler and faster models, but to provide a well founded understanding of their limitations and a means of improving them. An example of this is to use the physics-based wildland-urban interface fire dynamics simulator (WFDS) to develop and evaluate a simpler level set model of surface fire spread. A basic implementation of the level set model performs reasonably well but requires further evaluation when applied to scenarios that include heterogeneous fuels and the potential influence of fire induced winds.
The advancement of three-dimensional, time-dependent fire behaviour models is best supported by p... more The advancement of three-dimensional, time-dependent fire behaviour models is best supported by publicly available, co-located, synchronised, quality-assured measures of pre-fire, active fire and post-fire conditions (i.e. integrated datasets). Currently, there is a lack of such datasets. Consequently, we discuss essential components to produce integrated datasets: metadata, implementation of geospatial and temporal standards, data management plans, quality assurance project plans and data quality objectives. We present example data quality objectives and a data model for grassland experiments developed based on our experience integrating data from the 2014 Camp Swift Fire and the 2012 Prescribed Fire Combustion and Atmospheric Dynamics Research experiments.
Wildland fire and ecological researchers use empirical and semi-empirical modeling systems to ass... more Wildland fire and ecological researchers use empirical and semi-empirical modeling systems to assess fire behavior and danger. This technical note describes the firebehavioR package, a porting of two fire behavior modeling systems, Crown Fire Initiation and Spread and a Rothermel-based framework, to the R programming language. We also highlight supporting data objects and functions to predict inputs required for fire behavior estimation. Last, this package contains functions for fifteen indices to express fire danger using weather and/or fuels observations. Specific advantages of predicting fire behavior using R, a free-and-open-source programming language, include freedom to adapt calculations to suit users’ needs, transparency of source code, and reduction of workflow inefficiencies, thereby aiding in sophisticated fire behavior analyses.
To pursue the development and validation of coupled fire-atmosphere models, the wildland fire mod... more To pursue the development and validation of coupled fire-atmosphere models, the wildland fire modeling community needs validation data sets with scenarios where fire-induced winds influence fire front behavior, and with high temporal and spatial resolution. Helicopter-borne infrared thermal cameras have the potential to monitor landscape-scale wildland fires at a high resolution during experimental burns. To extract valuable information from those observations, three-step image processing is required: (a) Orthorectification to warp raw images on a fixed coordinate system grid, (b) segmentation to delineate the fire front location out of the orthorectified images, and (c) computation of fire behavior metrics such as the rate of spread from the time-evolving fire front location. This work is dedicated to the first orthorectification step, and presents a series of algorithms that are designed to process handheld helicopter-borne thermal images collected during savannah experimental bur...
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