Fuel model

Last updated

A Fuel Model is a stylized set of fuel bed characteristics used as input for a variety of wildfire modeling applications. Wildfire behavior models, such as those of Rothermel, [1] take into account numerous empirical variables. While these inputs are important for equation outputs, they are often difficult and time-consuming, if not impossible, to measure for each fuel bed. A fuel model defines these input variables for a stylized set of quantitative vegetation characteristics that can be visually identified in the field. Depending on local conditions, one of several fuel models may be appropriate. As Anderson states “Fuel models are simply tools to help the user realistically estimate fire behavior. The user must maintain a flexible frame of mind and an adaptive method of operating to totally utilize these aids". [2] Furthermore, depending on the application, the user must choose a fuel model classification system. The major classification systems for use in the United States include the National Fire Danger Rating System, the 13 ‘original’ fuel models of Anderson and Albini, the subsequent set of 40 fuels produced by Scott and Burgan, and the Fuel Characteristics Classification System.

Contents

National Fire Danger Rating System

The concept of a fuel model was first introduced in 1972 with the National Fire Danger Rating System. The first system of its kind, the NFDRS was a standardized set of equations to determine fire danger at specific points on the landscape. [3] Fuel models were at the core of these calculations, with each of its 20 models containing information about the relative loading of different fuel components. Each model is described by the volume of 1-hr, 10-hr, 100-hr, and 1000-hr dead fuels, herbaceous and woody live fuels present as well as the fuel bed depth and moisture of extinction.

NFDRS ModelName
AWestern grasses (annual)
C Pine-grass Savanna
DSouthern rough
EHardwood litter (winter)
FIntermediate brush
GShort needle (heavy dead)
HShort needle (normal dead)
IHeavy slash
JIntermediate slash
KLight slash
LWestern grasses (perennial)
N Sawgrass
OHigh pocosin
PSouthern pine plantation
Q Alaskan black spruce
RHardwood litter (summer)
S Tundra
T Sagebrush-grass
UWestern pines

Albini and Anderson's Models

The ‘original 13 fuel models’ were presented first by Albini [4] in 1976 and later expanded upon by Anderson [5] in 1982. Unlike the NFDRS, these fuel models were designed for use with Rothermel's spread models, and are designed to be used at much smaller spatial scales than the 20 NFDRS models. To allow interchangeability between the two systems, Anderson's report contains a crosswalk chart to allow conversion between similar models. Furthermore, his paper includes photographs to aid the user in selecting a fuel model. These fire behavior fuel models are “for the severe period of the fire season when wildfires pose greater control problems,” and are designed only for use during the dry season, when the fuel bed becomes more uniform. Additionally, Albini's models have the following assumptions:

  1. Ovendry fuel density = 32 lb/ft^3
  2. Heat of combustion = 8.000 btu/lb
  3. Total Mineral Content = 5.55%
  4. Silica-free ash content/effective mineral content = 1.00%

These models quantitatively describe the same fuel loading components as the NFDRS models, and are grouped into four classes: grass, shrub, timber, and slash.

Grass Group:

Model NumberName
1Short Grass
2Timber Grass and Understory
3Tall Grass

Shrub Group:

Model NumberName
4 Chaparral
5Brush
6Dormant Brush
7Southern Rough

Timber Group:

Model NumberName
8Compact Timber Litter
9Hardwood Litter
10Timber Understory

Slash Group:

Model NumberName
11Light Slash
12Medium Slash
13Heavy Slash

Scott and Burgan's Dynamic Models

Scott and Burgan's Dynamic Fuel Models were published [6] in 2005 to eliminate the assumption that the fuel bed was uniform during the dry season. This is done through the use of dynamic herbaceous fuel beds, where the “live herbaceous load is transferred to dead as a function of the live herbaceous moisture content.” The use of a curing coefficient allows more realistic modeling of fire behaviors in herbaceous fuel beds. Furthermore, these models aim to move away from the correlation between vegetation type and fuel bed characteristics. For example, the original ‘chaparral’ model becomes the ‘heavy load, tall brush” model. Like the NFDRS conversion crosswalk in Albini and Anderson's models, Scott and Burgan include a crosswalk between the original 13 and their set of 40 new models. Furthermore, they include the original 13 as models 1–13 to allow backwards compatibility in newer modeling software.

Key to selecting a dynamic fuel model

1. Nearly pure grass and/or forb type (Grass)

a. Arid to semiarid climate (rainfall deficient in summer). Extinction moisture content is 15 percent.
b. Sub-humid to humid climate (rainfall adequate in all seasons). Extinction moisture content is 30 to 40 percent.

2. Mixture of grass and shrub, up to about 50 percent shrub coverage (Grass-Shrub)

a. Arid to semiarid climate (rainfall deficient in summer). Extinction moisture content is 15 percent.
b. Sub-humid to humid climate (rainfall adequate in all seasons). Extinction moisture content is 30 to 40 percent.

3. Shrubs cover at least 50 percent of the site; grass sparse to nonexistent (Shrub)

a. Arid to semiarid climate (rainfall deficient in summer). Extinction moisture content is 15 percent.
b. Sub-humid to humid climate (rainfall adequate in all seasons). Extinction moisture content is 30 to 40 percent.

4. Grass or shrubs mixed with litter from forest canopy (Timber-Understory)

a. Semiarid to sub-humid climate. Extinction moisture content is 20 percent.
b. Humid climate. Extinction moisture content is 30 percent.

5. Dead and down woody fuel (litter) beneath a forest canopy (Timber Litter)

a. Fuel bed is recently burned but able to carry wild-land fire.
b. Fuel bed not recently burned.
i. Fuel bed composed of broad-leaf (hardwood) litter.
ii. Fuel bed composed of long-needle pine litter.
iii. Fuel bed not composed broad-leaf or long-needle pine litter.
1. Fuel bed includes both fine and coarse fuels.
2. Fuel bed does not include coarse fuels.

6. Activity fuel (slash) or debris from wind damage (blowdown) (Slash-Blowdown)

a. Fuel bed is activity fuel.
b. Fuel bed is blowdown.

7. Insufficient wildland fuel to carry wildland fire under any condition (non burnable)

Fuel Characteristic Classification System (FCCS)

Developed in 2007, the Fuel Characteristic Classification System [7] expands upon the existing fuel models to produce a set of stylized fuel beds with quantitative data on their ability to support Wild-land fire and the degree to which such a fire would consume the fuel lying within the bed. Regionally developed by teams of experts, these models were “compiled from scientific literature, fuels photo series, fuels data sets, and expert opinion.” In addition to the standard dead and live components, the FCCS scheme reports assigned and calculated fuel characteristics for each existing fuel bed stratum including the canopy, shrubs, non-woody, woody, litter-lichen-moss, and duff,” allowing a more comprehensive analysis of material within a fuel bed. Furthermore, “the system classifies each fuel bed by calculating fire potentials that provide an index of the intrinsic capacity of each fuel bed to support surface fire behavior, support crown fire, and provide fuels for flaming, smoldering, and residual consumption.” The FCCS has significant potential, but has not be integrated into mainstream modeling software such as Flammap or Farsite. However, they are gaining popularity in modeling wildland fire emissions and in the development of fuel bed, fire hazard, and treatment effectiveness maps on several national forests. Unlike the Scott and Burgan Models which move away from the use of vegetation type as a proxy for fuel type, the FCCS relies heavily on vegetation type in the formation of its models.

Sources

  1. Rothermel, Richard C. A Mathematical Model for Predicting Fire Spread in Wildland Fuels. USDA Forest Service. Research Paper INT-115. 1972.
  2. Anderson, Hal E. Aids to Determining Fuel Models for Estimating Fire Behavior. USDA Forest Service. General Technical Report INT-122. 1982.
  3. Cohen, Jack D. and Jack Deeming "The National Fire Danger Rating System: Basic Equations." USDA Forest Service. General Technical Report PSW-82. 1985
  4. Albini, Frank.Estimating Wildfire Behavior and Effects. USDA Forest Service. General Technical Report INT-30. 1976
  5. Anderson, Hal E. Aids to Determining Fuel Models for Estimating Fire Behavior. USDA Forest Service. General Technical Report INT-122. 1982.
  6. Scott, Joe H. and Robert E. Burgan. "Standard Fire Behavior Fuel Models: A Comprehensive Set for Use with Rothermel's Surface Fire Spread Model." USDA Forest Service. General Technical Report RMRS-GTR-153. 2005
  7. Ottmar, Roger D.; et al. (2007). "An Overview of the Fuel Characteristic Classification System - Quantifying, Classifying, and Creating Fuel beds for Resource Planning". Canadian Journal of Forest Research. 37: 2383–2393. doi:10.1139/x07-077.

Bibliography

Related Research Articles

<span class="mw-page-title-main">Chaparral</span> Shrubland plant community in western North America

Chaparral is a shrubland plant community found primarily in California, in southern Oregon and in the northern portion of the Baja California Peninsula in Mexico. It is shaped by a Mediterranean climate and infrequent, high-intensity crown fires.

<span class="mw-page-title-main">Tropical and subtropical grasslands, savannas, and shrublands</span> Terrestrial habitat type defined by the World Wide Fund for Nature

Tropical and subtropical grasslands, savannas, and shrublands is a terrestrial biome defined by the World Wide Fund for Nature. The biome is dominated by grass and/or shrubs located in semi-arid to semi-humid climate regions of subtropical and tropical latitudes. Tropical grasslands are mainly found between 5 degrees and 20 degrees in both North and south of the Equator.

<span class="mw-page-title-main">Great Basin Desert</span> Desert in the western United States

The Great Basin Desert is part of the Great Basin between the Sierra Nevada and the Wasatch Range. The desert is a geographical region that largely overlaps the Great Basin shrub steppe defined by the World Wildlife Fund, and the Central Basin and Range ecoregion defined by the U.S. Environmental Protection Agency and United States Geological Survey. It is a temperate desert with hot, dry summers and snowy winters. The desert spans large portions of Nevada and Utah, and extends into eastern California. The desert is one of the four biologically defined deserts in North America, in addition to the Mojave, Sonoran, and Chihuahuan Deserts.

<span class="mw-page-title-main">Oxisol</span> Soil type known for occurring in tropical rain forests

Oxisols are a soil order in USDA soil taxonomy, best known for their occurrence in tropical rain forest within 25 degrees north and south of the Equator. In the World Reference Base for Soil Resources (WRB), they belong mainly to the ferralsols, but some are plinthosols or nitisols. Some oxisols have been previously classified as laterite soils.

<span class="mw-page-title-main">Rangeland</span> Biomes which can be grazed by animals or livestock (grasslands, woodlands, prairies, etc)

Rangelands are grasslands, shrublands, woodlands, wetlands, and deserts that are grazed by domestic livestock or wild animals. Types of rangelands include tallgrass and shortgrass prairies, desert grasslands and shrublands, woodlands, savannas, chaparrals, steppes, and tundras. Rangelands do not include forests lacking grazable understory vegetation, barren desert, farmland, or land covered by solid rock, concrete, or glaciers.

This glossary of wildfire terms is a list of definitions of terms and concepts relevant to wildfires and wildland firefighting. Except where noted, terms have largely been sourced from a 1998 Fireline Handbook transcribed for a Conflict 21 counter-terrorism studies website by the Air National Guard.

<span class="mw-page-title-main">Fire ecology</span> Study of fire in ecosystems

Fire ecology is a scientific discipline concerned with the effects of fire on natural ecosystems. Many ecosystems, particularly prairie, savanna, chaparral and coniferous forests, have evolved with fire as an essential contributor to habitat vitality and renewal. Many plant species in fire-affected environments use fire to germinate, establish, or to reproduce. Wildfire suppression not only endangers these species, but also the animals that depend upon them.

<span class="mw-page-title-main">Tiger bush</span> Topographic lines of vegetation arising from differential absorption of rainfall

Tiger bush, or brousse tigrée in the French language, is a patterned vegetation community and ground consisting of alternating bands of trees, shrubs, or grass separated by bare ground or low herb cover, that run roughly parallel to contour lines of equal elevation. The patterns occur on low slopes in arid and semi-arid regions, such as in Australia, Sahelian West Africa, and North America.

<span class="mw-page-title-main">Wildfire suppression</span> Firefighting tactics used to suppress wildfires

Wildfire suppression is a range of firefighting tactics used to suppress wildfires. Firefighting efforts depend on many factors such as the available fuel, the local atmospheric conditions, the features of the terrain, and the size of the wildfire. Because of this wildfire suppression in wild land areas usually requires different techniques, equipment, and training from the more familiar structure fire fighting found in populated areas. Working in conjunction with specially designed aerial firefighting aircraft, fire engines, tools, firefighting foams, fire retardants, and using various firefighting techniques, wildfire-trained crews work to suppress flames, construct fire lines, and extinguish flames and areas of heat in order to protect resources and natural wilderness. Wildfire suppression also addresses the issues of the wildland–urban interface, where populated areas border with wild land areas.

<span class="mw-page-title-main">Yellowstone fires of 1988</span> Natural event in Yellowstone National Park, United States

The Yellowstone fires of 1988 collectively formed the largest wildfire in the recorded history of Yellowstone National Park in the United States. Starting as many smaller individual fires, the flames quickly spread out of control due to drought conditions and increasing winds, combining into several large conflagrations which burned for several months. The fires almost destroyed two major visitor destinations and, on September 8, 1988, the entire park was closed to all non-emergency personnel for the first time in its history. Only the arrival of cool and moist weather in the late autumn brought the fires to an end. A total of 793,880 acres (3,213 km2), or 36 percent of the park, burned at varying levels of severity.

National Fire Danger Rating System (NFDRS) is used in the United States to provide a measure of the relative seriousness of burning conditions and threat of wildfires.

Wildfires consume live and dead fuels, destabilize physical and ecological landscapes, and impact human social and economic systems. Post-fire seeding was initially used to stabilize soils. More recently it is being used to recover post wildfire plant species, manage invasive non-native plant populations and establish valued vegetation compositions.

<span class="mw-page-title-main">Wildfire modeling</span>

Wildfire modeling is concerned with numerical simulation of wildfires to comprehend and predict fire behavior. Wildfire modeling aims to aid wildfire suppression, increase the safety of firefighters and the public, and minimize damage. Wildfire modeling can also aid in protecting ecosystems, watersheds, and air quality.

A fire regime is the pattern, frequency, and intensity of the bushfires and wildfires that prevail in an area over long periods of time. It is an integral part of fire ecology, and renewal for certain types of ecosystems. A fire regime describes the spatial and temporal patterns and ecosystem impacts of fire on the landscape, and provides an integrative approach to identifying the impacts of fire at an ecosystem or landscape level. If fires are too frequent, plants may be killed before they have matured, or before they have set sufficient seed to ensure population recovery. If fires are too infrequent, plants may mature, senesce, and die without ever releasing their seed.

<span class="mw-page-title-main">Fossil record of fire</span> Fossilized evidence of wildfires on Earth

The fossil record of fire first appears with the establishment of a land-based flora in the Middle Ordovician period, 470 million years ago, permitting the accumulation of oxygen in the atmosphere as never before, as the new hordes of land plants pumped it out as a waste product. When this concentration rose above 13%, it permitted the possibility of wildfire. Wildfire is first recorded in the Late Silurian fossil record, 420 million years ago, by fossils of charcoalified plants. Apart from a controversial gap in the Late Devonian, charcoal is present ever since. The level of atmospheric oxygen is closely related to the prevalence of charcoal: clearly oxygen is the key factor in the abundance of wildfire. Fire also became more abundant when grasses radiated and became the dominant component of many ecosystems, around 6 to 7 million years ago; this kindling provided tinder which allowed for the more rapid spread of fire. These widespread fires may have initiated a positive feedback process, whereby they produced a warmer, drier climate more conducive to fire.

The wildland–urban interface (WUI) is a zone of transition between wilderness and land developed by human activity – an area where a built environment meets or intermingles with a natural environment. Human settlements in the WUI are at a greater risk of catastrophic wildfire.

<span class="mw-page-title-main">Mediterranean forests, woodlands, and scrub</span> Habitat defined by the World Wide Fund for Nature

Mediterranean forests, woodlands and scrub is a biome defined by the World Wide Fund for Nature. The biome is generally characterized by dry summers and rainy winters, although in some areas rainfall may be uniform. Summers are typically hot in low-lying inland locations but can be cool near colder seas. Winters are typically mild to cool in low-lying locations but can be cold in inland and higher locations. All these ecoregions are highly distinctive, collectively harboring 10% of the Earth's plant species.

<span class="mw-page-title-main">Wildfire emergency management</span>

Wildfires are outdoor fires that occur in the wilderness or other vast spaces. Other common names associated with wildfires are brushfire and forest fire. Since wildfires can occur anywhere on the planet, except for Antarctica, they pose a threat to civilizations and wildlife alike. In terms of emergency management, wildfires can be particularly devastating. Given their ability to destroy large areas of entire ecosystems, there must be a contingency plan in effect to be as prepared as possible in case of a wildfire and to be adequately prepared to handle the aftermath of one as well.

<span class="mw-page-title-main">Wildfires in the United States</span> Wildfires that occur in the United States

Wildfires can happen in many places in the United States, especially during droughts, but are most common in the Western United States and Florida. They may be triggered naturally, most commonly by lightning, or by human activity like unextinguished smoking materials, faulty electrical equipment, overheating automobiles, or arson.

<span class="mw-page-title-main">Pyrogeography</span> Study of the distribution of wildfires

Pyrogeography is the study of the past, present, and projected distribution of wildfire. Wildland fire occurs under certain conditions of climate, vegetation, topography, and sources of ignition, such that it has its own biogeography, or pattern in space and time. The earliest published evidence of the term appears to be in the mid-1990s, and the meaning was primarily related to mapping fires The current understanding of pyrogeography emerged in the 2000s as a combination of biogeography and fire ecology, facilitated by the availability of global-scale datasets of fire occurrence, vegetation cover, and climate. Pyrogeography has also been placed at the juncture of biology, the geophysical environment, and society and cultural influences on fire.