United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

General Technical

Report RMRS-GTR-153

June 2005

Standard Fire Behavior Fuel

Models: A Comprehensive

Set for Use with Rothermel’s

Surface Fire Spread Model

Joe H. Scott

Robert E. Burgan
Abstract ________________________________________

Scott, Joe H.; Burgan, Robert E. 2005. Standard fire behavior fuel models: a comprehensive

set for use with Rothermel’s surface fire spread model. Gen. Tech. Rep. RMRS-GTR-153.

Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research

Station. 72 p.

This report describes a new set of standard fire behavior fuel models for use with Rothermel’s

surface fire spread model and the relationship of the new set to the original set of 13 fire behavior

fuel models. To assist with transition to using the new fuel models, a fuel model selection guide,

fuel model crosswalk, and set of fuel model photos are provided.

Keywords: fire behavior prediction, fire modeling, surface fuel, dynamic fuel model

The Authors _____________________________________

Joe H. Scott has been a Forester with Systems for Environmental Management, a

nonprofit research group based in Missoula, MT, since 1996. He is the lead developer of

NEXUS, a system for assessing crown fire potential; lead developer of FireWords, an

annotated, electronic glossary of fire science terminology; and codeveloper of FuelCalc,

a system for computing, summarizing, and formatting ground, surface, and crown fuel

characteristics from standard inventory methods. Scott has participated in several investigations of surface and canopy fuel characteristics. He has a B.S. degree in forestry and

resource management from the University of California at Berkeley and an M.S. degree in

forestry from the University of Montana.

Robert E. Burgan retired as a Supervisory Research Forester, Applications Team, Fire

Behavior Research, Intermountain Fire Sciences Laboratory, Missoula, MT. He was one

of the developers of the 1978 National Fire Danger Rating System and made the 1988

revisions of the 1978 NFDRS. Burgan developed the fuels portion of the BEHAVE fire

behavior prediction system. He was the lead Forest Service scientist, working with

scientists at the USGS EROS Data Center, to develop the greenness maps now used to

assess fire potential nationally. He was the lead scientist in developing a national 1-km

resolution fuel model map from the Land Cover Characteristics Database provided by the

EROS Data Center. He was the initial developer of the Fire Potential Index and has worked

closely with EROS Data Center scientists and others to improve and implement it.
You may order additional copies of this publication by sending your

mailing information in label form through one of the following media.

Please specify the publication title and number.

Telephone (970) 498-1392

FAX (970) 498-1122

E-mail rschneider@fs.fed.us

Web site http://www.fs.fed.us/rm/publications

Mailing Address Publications Distribution

Rocky Mountain Research Station

240 West Prospect Road

Fort Collins, CO 80526

Acknowledgments ______________

We are grateful for thoughtful comments on the draft

fuel model set or HTML application provided by: Collin

Bevins, Systems for Environmental Management; J.D.

Carlson, Oklahoma State University; Don Carlton, Fire

Program Solutions, LLC; Corky Conover, Sequoia National Park; Wayne Cook, Washington Office Fire Technology Transfer Program; Dave Engle, Oklahoma State

University; Kato Howard, Alaska Fire Service; Randi

Jandt, Alaska Fire Service; Paul Langowski, USFS Rocky

Mountain Region; Duncan Lutes, Systems for Environmental Management; Melanie Miller, BLM (stationed at

Missoula Fire Sciences Lab); Rob Seli, Missoula Fire

Sciences Lab; Dale Wade, Southern Research Station

(retired); Dave Whitmer, Alaska Fire Service; and Robert

Ziel, Michigan Department of Natural Resources. For

their reviews of the manuscript we also thank Patricia

Andrews and Mark Finney, Missoula Fire Sciences Lab;

James K. Agee, University of Washington; Sam Sandberg,

FERA Pacific Fire Sciences Lab; and Jennifer L. Long,

Systems for Environmental Management.

Photos to illustrate fuel models were provided by

Roger Ottmar, Pacific Fire Sciences Laboratory, Pacific

Northwest Research Station; Bob Burgan, Missoula

Fire Sciences Lab (retired); Joe Scott, Systems for

Environmental Management; and other published photo

guides.

Funding for the development of a new set of standard

fire behavior fuel models and the preparation of this

document was provided by the LANDFIRE project, USDA

Forest Service, Rocky Mountain Research Station. This

project was conducted under contract with Systems for

Environmental Management, Missoula, MT.

Contents________________________________________

Page

Introduction ........................................................................................................................... 1

Need ................................................................................................................................. 2

Scope................................................................................................................................ 3

Development..................................................................................................................... 3

Characteristics ...................................................................................................................... 4

Naming Convention .......................................................................................................... 4

Dynamic Fuel Models ....................................................................................................... 6

Moisture Scenarios ........................................................................................................... 8

Fuel Model Selection............................................................................................................. 8

Fuel Model Selection Guide.............................................................................................. 8

Fuel Model Crosswalks................................................................................................... 12

Fuel Models......................................................................................................................... 17

Fuel Model Parameters .................................................................................................. 17

Fuel Type Page .............................................................................................................. 17

Fuel Model Page............................................................................................................. 19

Nonburnable Fuel Type Models (NB) ............................................................................. 19

Grass Fuel Type Models (GR) ........................................................................................ 25

Grass-Shrub Fuel Type Models (GS) ............................................................................. 35

Shrub Fuel Type Models (SH) ........................................................................................ 40

Timber-Understory Fuel Type Models (TU) .................................................................... 50

Timber Litter Fuel Type Models (TL) .............................................................................. 56

Slash-Blowdown Fuel Type Models (SB) ....................................................................... 66

References .......................................................................................................................... 71

Standard Fire Behavior Fuel Models: A Comprehensive Set

for Use with Rothermel’s Surface Fire Spread Model

Joe H. Scott

Robert E. Burgan

USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 1

Introduction ______________________________________________________

Predicting the potential behavior and effects of wildland fire is an essential task in fire

management. Mathematical surface fire behavior and fire effects models and prediction

systems are driven in part by fuelbed inputs such as load, bulk density, fuel particle size,

heat content, and moisture of extinction. To facilitate use in models and systems, fuelbed

inputs have been formulated into fuel models. A fuel model is a set of fuelbed inputs

needed by a particular fire behavior or fire effects model. Different kinds of fuel models

are used in fire science; this document addresses only fire behavior fuel models for use

in the Rothermel (1972) surface fire spread model.

Fire behavior fuel models are used as input to the Rothermel (1972) fire spread model,

which is used in a variety of fire behavior modeling systems. The fire behavior fuel model

input set includes:

• Fuel load by category (live and dead) and particle size class (0 to 0.25 inch, 0.25

to 1.0 inch, and 1.0 to 3.0 inches diameter)

• Surface-area-to-volume (SAV) ratio by component and size class

• Heat content by category

• Fuelbed depth

• Dead fuel moisture of extinction.

The National Fire Danger Rating System (NFDRS; Deeming and others 1977) uses

Rothermel’s (1972) spread model as its core. However, there are differences in the

calculations that require the use of different fuel models than those for fire behavior

prediction. Therefore, there is a separate set of fuel models for use within NFDRS. This

paper does not address NFDRS fuel models; they are not affected by this work. The fuel

models described here should not be used in the NFDRS.

Rothermel (1972) defined a fire behavior fuel model as a “complete set of [fuel] inputs

for the mathematical fire spread model,” and listed parameters for 11 fuel models. To

assist in understanding the sensitivity of certain inputs, Rothermel held constant the fuel

particle properties (total and effective mineral content, heat content, and particle

density). Extinction moisture content was not listed for each fuel model separately, but

instead held at 30 percent for all models. Thus, variation in predicted spread rate among

models could be attributed to fuel load by size class, fuelbed depth, and fuel particle size.

Parameters for 10-hr and 100-hr SAV were listed for each fuel model, but did not vary

among models – 109 1/ft and 30 1/ft, respectively.

Albini (1976) refined those 11 fuel models and added two others, Dormant Brush (6)

and Southern Rough (7). His tabulated set became what is now called the original 13 fire

behavior fuel models. Whereas extinction moisture content was held constant for

Rothermel’s 11 fuel models, Albini’s fuel models specified this value for each fuel

Standard Fire Behavior Fuel

Models: A Comprehensive Set

for Use with Rothermel’s Surface

Fire Spread Model

Joe H. Scott

Robert E. Burgan
2 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

model. Albini noted that “other variables needed to complete the [fuel] descriptions are

held constant for the entire set.”

Anderson (1982) described the 13 fuel models listed by Albini and provided aids to

selecting a fuel model. Fuel model parameters did not change from Albini’s set.

Anderson listed as model parameters only fuel load by size class, fuelbed depth, and dead

fuel extinction moisture.

The BEHAVE fire behavior prediction and fuel modeling system (Andrews 1986;

Burgan and Rothermel 1984) included fuel particle heat content as a fuel model

parameter that could vary from model to model, whereas previous work had left that

parameter constant. FARSITE (Finney 1998) and BehavePlus (Andrews and others

2003) allow the user to specify separate live and dead heat content values. The ability to

specify heat content is primarily for greater precision when building a custom fuel model;

the original 13 fuel models still used a single value of 8000 BTU/lb for live and dead heat

content for all fuel models.

Although a fuel model technically includes all fuel inputs to the Rothermel surface fire

spread model, several fuel inputs have never been subject to control by a user when

creating a custom fuel model: total and effective mineral contents, and fuel particle

density. The 10-hr and 100-hr SAVs were listed as model parameters for the original 13

fuel models but are generally not subject to control of the user when making custom fuel

models in fire modeling systems. For the above reasons, we did not consider using values

for fuel particle properties or 10-hr and 100-hr SAVs other than the constant values

originally published by Rothermel (1972). We list as parameters only those fuel model

inputs that vary among models:

• Fuel load by size class and category

• Live woody, live herbaceous, and dead 1-hr SAV

• Fuelbed depth

• Dead fuel extinction moisture content

• Heat content of live and dead fuels

For all fuel models in this new set:

• 10-hr dead fuel SAV is 109 1/ft, and 100-hr SAV is 30 1/ft.

• Total mineral content is 5.55 percent; effective (silica-free) mineral content is

1.00 percent.

• Ovendry fuel particle density is 32 lb/ft3.

Need

The original 13 fire behavior fuel models are “for the severe period of the fire season

when wildfires pose greater control problems...” (Anderson 1982). Those fuel models

have worked well for predicting spread rate and intensity of active fires at peak of fire

season in part because the associated dry conditions lead to a more uniform fuel complex,

an important assumption of the underlying fire spread model (Rothermel 1972).

However, they have deficiencies for other purposes, including prescribed fire, wildland

fire use, simulating the effects of fuel treatments on potential fire behavior, and

simulating transition to crown fire using crown fire initiation models. Widespread use of

the Rothermel (1972) fire spread model and desire for more options in selecting a fuel

model indicate the need for a new set of models to:

• Improve the accuracy of fire behavior predictions outside of the severe period of

the fire season, such as prescribed fire and fire use applications. For example, the

original grass models 1 (short grass) and 3 (tall grass) are fully cured to represent

the most severe part of the fire season. Applying those fuel models to situations
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 3

in which the grass fuelbed is not fully cured (that is, outside the severe part of the

fire season) leads to overprediction.

• Increase the number of fuel models applicable in high-humidity areas. With the

Rothermel spread model, the only way to accommodate fuel complexes that burn

well at high humidity is through the moisture of extinction parameter. Only a few

of the original 13 fuel models are appropriate for fuelbeds that burn well at

relatively high dead fuel moistures.

• Increase the number of fuel models for forest litter and litter with grass or shrub

understory. Predicted surface fire behavior drives crown fire models (Alexander

1988; Van Wagner 1977), so increased precision in surface fire intensity

prediction will lead to increased precision in crown fire behavior prediction and

hazard assessment.

• Increase the ability to simulate changes in fire behavior as a result of fuel

treatment by offering more fuel model choices, especially in timber-dominated

fuelbeds. This fuel model set does not attempt to directly simulate the effects of

the wide variety of available fuel treatment options.

Scope

The development of a new set of standard fire behavior fuel models does not address

deficiencies in the Rothermel surface fire spread model itself. Like the original set of 13,

the new fire behavior fuel model set is applicable to fire behavior modeling systems that

use Rothermel’s surface fire spread model. Any description of the presence or absence

of overstory trees is due to their potential effect on surface fuels (for example, needle litter

in a grass fuel model).

Also like the original fuel models, the new set is for simulating surface fire behavior

at the flaming front only, not residual combustion that takes place after the flaming front

has passed. Other methods of describing fuel and other types of fuel models are used for

prediction of postfrontal combustion, fuel consumption, smoke production, and crown

fire behavior. The fuel model parameters presented in this set should not be used as

fuelbed characteristics for fuel consumption models.

Finally, the same fuelbed assumptions of homogeneity and continuity apply to these

as well as the original 13 fuel models (Rothermel 1972). Methods of addressing

heterogeneous or discontinuous fuels are available in fire modeling systems.

Development

We compiled fuel complex information from several volumes of the Natural Fuels

Photo Series (Ottmar and Vihnanek 1998, 1999, 2000, 2002; Ottmar and others 1998,

2000, 2002, 2003; Wright and others 2002) and other sources. The range of fuel complex

characteristics suggested the range of fuel conditions for which fuel models were needed.

We subjectively assigned a fire-carrying fuel type and dead fuel extinction moisture

content to each fuel complex, then grouped the complexes by fine fuel load, fuel type,

and extinction moisture. We created one fuel model for each of the approximately 60

groups. Surface-area-to-volume ratio for 1-hr timelag, live herbaceous and live woody

classes were assigned subjectively for each draft fuel model. Fuelbed depth was assigned

after subjective interpretation of fuel complex data and visual inspection of photographs.

Heat content of live and dead fuels is 8000 BTU/lb for all fuel models except GR6 (High

Load, Humid Climate Grass), which is 9000 BTU/lb for both live and dead fuels.

Next, we made fire behavior simulations over a range of midflame wind speeds and

several fuel moisture scenarios. Although the groups of fuel complexes appeared to be

distinct from one another, the fuel models we created from them often led to similar flame

length and rate of spread, so several models were eliminated. Also, after comparing fire
4 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

behavior outputs from the draft fuel model set with outputs from the original 13 fuel

models, we added stylized fuel models to simulate specific fire behavior characteristics

not simulated by any of the draft models. Finally, we adjusted the parameters of many

draft fuel models to better coordinate fire behavior outputs of related fuel models.

 The draft fuel model set was sent to more than three dozen fire science researchers

and managers for review; their comments were incorporated into the final fuel model set

and its documentation, which was reviewed again by a smaller cadre.

Characteristics ___________________________________________________

This new set of standard fire behavior fuel models is designed to stand alone; none of

the original 13 fire behavior fuel models is repeated in the new set; the fuel model

selection guide points to the new fuel models only. However, the original 13 fire behavior

fuel models will still be available, and they are still called fire behavior fuel models 1-

13. There is no immediate need to reanalyze existing fuel model maps or lookup tables

that are sufficient for their purpose. However, we anticipate that new fuel model mapping

projects will use this new set rather than the original 13.

Documentation and naming of the new fuel models refer to fuel or fuel types, not

vegetation or vegetation types. For example, what was formerly termed a “Chaparral”

fuel model might now be called a “Heavy Load, Tall Brush” model because one fuel

model can be applied in many vegetation types. Likewise, the fuel model selection guide

does not refer to specific vegetation types except as necessary to illustrate an example.

In this new set, all fuel models with an herbaceous component are dynamic. In a

dynamic fuel model, live herbaceous load is transferred to dead as a function of the live

herbaceous moisture content. Although the new fuel model parameters can be input to

a nondynamic fire behavior processor, that approach does not produce the intended

result. Using the dynamic fuel models in a nondynamic fire behavior model would leave

the live herbaceous load in the live category, regardless of moisture content. The grass

models will therefore predict no (or very little) spread and intensity under any wind or

moisture condition. The change to dynamic fuel models is really a change in both the fire

behavior processors and, concurrently, how fuel models for grass- or herbaceousdominated fuelbeds are conceived. In this case, our desire for grass and herbaceous fuel

models that could be used at various levels of curing precipitated the change in fire

behavior processors.

Fire behavior modeling systems must be modified in order to use the new dynamic fuel

models correctly. Check the documentation of each fire behavior processor to be sure it

implements the dynamic fuel models as intended.

Naming Convention

Fuel models in the new set are grouped by fire-carrying fuel type. The number of fuel

models within each fuel type varies. Each fuel type has been assigned a mnemonic twoletter code. Nonburnable fuel models, even though not really a “fuel,” were included in

the set to facilitate consistent mapping of these areas on a fuel model map. Fuel types were

ordered in a way similar to the original 13, with hybrid fuel types (such as TimberUnderstory) generally between the two types that compose the hybrid. Fuel types are as

follows:

• (NB) Nonburnable

• (GR) Grass

• (GS) Grass-Shrub

• (SH) Shrub

• (TU) Timber-Understory
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 5

• (TL) Timber Litter

• (SB) Slash-Blowdown

To facilitate both communication and computation, we use a three-part fuel model

reference scheme:

• Fuel model number (between 1 and 256; for use in computer code and mapping

applications)

• Fuel model code (three digits; used for oral and written communication and input

to fire modeling systems)

• Fuel model name (any length string of characters; used for description and longhand written communication)

For example:

number code name

101 GR1 Short, sparse, dry climate grass

Within a fuel type, fuel models are ordered by increasing heat per unit area (at 8 percent

dead, 75 percent live fuel moisture content). Wind speed and slope steepness do not affect

heat per unit area. Fuel model numbers were kept below 256 so that an eight-bit number

could be used for storing fuel model information in mapping or database applications.

Each fuel type has been assigned a block of fuel model numbers (table 1) so that fuel

model maps colored by fuel type are simple to create. For example, a coarse-scale map

(for which identifying a specific fuel model is not required) can be colored such that all

fuel model numbers in a block (representing a fuel type) are the same color. Only a

portion of each block is used by the new fuel model set. The unused fuel model numbers

are reserved for future standard fuel models and for custom fuel models. This allows

future standard and custom fuel models to be in the correct fuel type number block.

The dead fuel extinction moisture assigned to the fuel model defines the weightedaverage dead fuel moisture content at which the fire will no longer spread in the

Rothermel model. This modeling parameter is generally associated with climate (humid

versus dry), though fire science research has yet to explain the mechanism for the

association. Fuel models for dry climates tend to have lower dead fuel moistures of

extinction, while fuel models for humid-climate areas tend to have higher moistures of

extinction. Fuel model names (and the fuel model selection guide) include reference to

the general climate where the fuel model is found.

Table 1—Assignment of current fuel model numbers to standard and custom fuel models.

Fuel model Used in original Reserved for future Available for

Fuel type number block or new set standard fuel models custom fuel models

1-13 1-13

14-89 14-89

NB 90-99 91-93, 98-99a 94-95 90, 96-97

GR 100-119 101-109 110-112 100, 113-119

GS 120-139 121-124 125-130 120, 131-139

SH 140-159 141-149 150-152 140, 153-159

TU 160-179 161-165 166-170 160, 171-179

TL 180-199 181-189 190-192 180, 193-199

SB 200-219 201-204 205-210 200, 211-219

220-256 220-256

a

 The gap in the NB numbering sequence is to retain fuel model numbers 98 as open water and 99 as “rock” (bare

ground), as has been convention in FARSITE.
6 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

Dynamic Fuel Models

In this new set, all fuel models that have a live herbaceous component are “dynamic,”

meaning that their herbaceous load shifts between live and dead depending on the

specified live herbaceous moisture content. In the Fuel Models section, refer to the model

parameters list (“fuel model type” column) to see which models contain live herbaceous

load and are therefore dynamic.

The dynamic fuel model process is described by Burgan (1979); the method is outlined

and outlined below, with graphic presentation in figure 1.

• If live herbaceous moisture content is 120 percent or higher, the herbaceous fuels

are green, and all herbaceous load stays in the live category at the given moisture

content.

• If live herbaceous moisture content is 30 percent or lower, the herbaceous fuels

are considered fully cured, and all herbaceous load is transferred to dead

herbaceous.

• If live herbaceous moisture content is between 30 and 120 percent, then part of

the herb load is transferred to dead. For example, if live herb moisture content is

75 percent (halfway between 30 and 120 percent), then half of the herbaceous

load is transferred to dead herbaceous, the remainder stays in the live herbaceous

class.

Load transferred to dead is not simply placed in the dead 1-hr timelag class. Instead

a new dead herbaceous class is created so that the surface-area-to-volume ratio of the live

herbaceous component is preserved. However, for simplicity the moisture content of the

new dead herbaceous category is set to the same as that for the dead 1-hr timelag class.

When evaluating dynamic models, be aware that live herbaceous moisture content

significantly affects fire behavior because herbaceous load shifts between live and dead,

and dead fuel usually has much lower moisture content than live. It will often be

preferable to estimate live herbaceous moisture content by working backward from

observed or estimated degree of herbaceous curing (table 2). For example, if the fuelbed

is observed to be 50 percent cured, use a value of 75 percent for live herbaceous moisture

content.

Figure 1—Graphical representation of the dynamic fuel model process.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 7

None of the original 13 fire behavior fuel models is dynamic. Therefore, direct

comparisons between the new and original fuel models can only be made if the live

herbaceous moisture content is 30 percent (fully cured) or lower. For example, models

GR6 and GR8 are similar to original fuel model 3, but their behavior over a range of live

herbaceous moisture content is very different (fig. 2). Fuel model 3 does not have a live

herbaceous component, so its behavior does not change as that input is varied. Fuel

models GR6 and GR8 are both dynamic, so fire behavior decreases rapidly with higher

levels of live fuel moisture (less curing).

To preserve the static nature of original fuel model 2 (which contains live herbaceous

load as well as dead grass) and to preserve the ability to create custom fuel models in

which dynamic load transfer does not take place, the fuel model description includes a

fuel model type. A static fuel model with live herbaceous load should keep that load in

the live category regardless of moisture content, whereas the same fuel model would

undergo the load transfer if its type is dynamic. Custom fuel models can be either static

or dynamic. If a fuel model does not have load in the live herbaceous category, then the

fuel model type is irrelevant.

Table 2—Level of curing versus live herbaceous moisture content.

Level of curing Live herbaceous moisture content

Uncured 0 percent 120 percent or more

One-quarter 25 98

One-third 33 90

One-half 50 75

Two-thirds 66 60

Three-quarters 75 53

Fully cured 100 30 or less

Figure 2—Comparison of dynamic fuel models GR6 and

GR8 with static fuel model 3.
8 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

Moisture Scenarios

To facilitate standard comparisons of the new fire behavior fuel models with the

original 13 fuel models and with each other, we developed standard dead (table 3) and

live (table 4) fuel moisture scenarios. Separate live and dead scenarios were needed so

that live and dead fuels could vary independently. There are 16 unique moisture scenario

combinations. However, fire behavior predicted with fuel models without a live fuel

component is not affected by the live moisture scenario. Live moisture scenarios cover

a range of live herbaceous moisture corresponding to fully cured (30 percent) to uncured

(fully green; 120 percent).

Table 3—Dead fuel moisture content values (percent) for

the dead fuel moisture scenarios.

D1 D2 D3 D4

Very low Low Moderate High

1-hr 3 6 9 12

10-hr 4 7 10 13

100-hr 5 8 11 14

Table 4—Live fuel moisture content values (percent) for the live fuel moisture scenarios.

L1 L2 L3 L4

Fully cured Two-thirds cured One-third cured Fully green (uncured)

Very low Low Moderate High

Live herbaceous 30 60 90 120

Live woody 60 90 120 150

Fuel Model Selection_______________________________________________

This document contains two aids to fuel model selection: a fuel model selection guide

and a set of crosswalks. Use the crosswalks if you have an area already designated as one

of the 13 original fuel models and you want guidance on selecting one of the new models

for that area. Use the fuel model selection guide for assistance in selecting a fuel model

from knowledge of general fuelbed properties.

Both the selection guide and crosswalks offer suggestions to consider, not conclusive

results. The final fuel model selection must be made by the user based on experience with

fire behavior in the fuelbed under consideration.

Fuel Model Selection Guide

To select a fuel model:

1. Determine the general fire-carrying fuel type: grass, grass-shrub, shrub, timber

litter, timber with (grass or shrub) understory, or slash or blowdown fuels. Estimate

which stratum of surface fuels is most likely to carry the fire. For example, the fire may

be in a forested area, but if the forest canopy is open, grass, not needle litter, might carry

the fire. In this case a grass model should be considered.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 9

2. The dead fuel extinction moisture assigned to the fuel model defines the moisture

content of dead fuels at which the fire will no longer spread. This fuel parameter, unique

to the Rothermel surface fire spread model, is generally associated with climate (humid

versus dry). That is, fuel models for dry areas tend to have lower dead fuel moistures of

extinction, while fuel models for wet humid areas tend to have higher moistures of

extinction.

3. Note the general depth, compactness, and size of the fuel, and the relative amount

of live vegetation.

4. Do not restrict your selection by fuel model name or fuel type. After selecting a

fuel model, view its predicted fire behavior to be sure the predicted behavior agrees with

your expectation or observation.

In this guide we refer to spread rates and flame lengths as being very low, low,

moderate, high, very high, and extreme—assuming two-thirds cured herbaceous, dry

dead fuels (moisture scenario D2L2), a midflame wind speed of 5 mi/h, and zero slope

(table 5).

Table 5—Adjective class definitions for predicted fire behavior.

Adjective class ROS (ch/h) FL (ft)

Very Low 0-2 0-1

Low 2-5 1-4

Moderate 5-20 4-8

High 20-50 8-12

Very High 50-150 12-25

Extreme >150 >25
10 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

The general fire-carrying fuel type is:

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

a. Arid to semiarid climate (rainfall deficient in summer). Extinction moisture

content is 15 percent.

i. GR1 Grass is short, patchy, and possibly heavily grazed. Spread rate

moderate; flame length low.

ii. GR2 Moderately coarse continuous grass, average depth about 1 foot.

Spread rate high; flame length moderate.

iii. GR4 Moderately coarse continuous grass, average depth about 2 feet.

Spread rate very high; flame length high.

iv. GR7 Moderately coarse continuous grass, average depth about 3 feet.

Spread rate very high; flame length very high.

b. Subhumid to humid climate (rainfall adequate in all seasons). Extinction

moisture content is 30 to 40 percent.

i. GR1 Grass is short, patchy, and possibly heavily grazed. Spread rate

moderate; flame length low.

ii. GR3 Very coarse grass, average depth about 2 feet. Spread rate high; flame

length moderate.

iii. GR5 Dense, coarse grass, average depth about 1 to 2 feet. Spread rate very

high; flame length high.

iv. GR6 Dryland grass about 1 to 2 feet tall. Spread rate very high; flame

length very high.

v. GR8 Heavy, coarse, continuous grass 3 to 5 feet tall. Spread rate very high;

flame length very high.

vi. GR9 Very heavy, coarse, continuous grass 5 to 8 feet tall. Spread rate

extreme; flame length extreme.

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

a. Arid to semiarid climate (rainfall deficient in summer). Extinction moisture

content is 15 percent.

i. GS1 Shrubs are about 1 foot high, low grass load. Spread rate moderate;

flame length low.

ii. GS2 Shrubs are 1 to 3 feet high, moderate grass load. Spread rate high;

flame length moderate.

b. Subhumid to humid climate (rainfall adequate in all seasons). Extinction

moisture content is 30 to 40 percent.

i. GS3 Moderate grass/shrub load, average grass/shrub depth less than 2 feet.

Spread rate high; flame length moderate.

ii. GS4 Heavy grass/shrub load, depth greater than 2 feet. Spread rate high;

flame length very high.

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.

i. SH1 Low shrub fuel load, fuelbed depth about 1 foot; some grass may be

present. Spread rate very low; flame length very low.

ii. SH2 Moderate fuel load (higher than SH1), depth about 1 foot, no grass

fuel present. Spread rate low; flame length low.

iii. SH5 Heavy shrub load, depth 4 to 6 feet. Spread rate very high; flame

length very high.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 11

iv. SH7 Very heavy shrub load, depth 4 to 6 feet. Spread rate lower than SH5,

but flame length similar. Spread rate high; flame length very high.

b. Subhumid to humid climate (rainfall adequate in all seasons). Extinction

moisture content is 30 to 40 percent.

i. SH3 Moderate shrub load, possibly with pine overstory or herbaceous fuel,

fuel bed depth 2 to 3 feet. Spread rate low; flame length low.

ii. SH4 Low to moderate shrub and litter load, possibly with pine overstory,

fuel bed depth about 3 feet. Spread rate high; flame length moderate.

iii. SH6 Dense shrubs, little or no herb fuel, depth about 2 feet. Spread rate

high; flame length high.

iv. SH8 Dense shrubs, little or no herb fuel, depth about 3 feet. Spread rates

high; flame length high.

v. SH9 Dense, finely branched shrubs with significant fine dead fuel, about

4 to 6 feet tall; some herbaceous fuel may be present. Spread rate high,

flame length very high.

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

a. Semiarid to subhumid climate. Extinction moisture content is 20 percent.

i. TU1 Fuelbed is low load of grass and/or shrub with litter. Spread rate low;

flame length low.

ii. TU4 Fuelbed is short conifer trees with grass or moss understory. Spread

rate moderate; flame length moderate.

iii. TU5 Fuelbed is high load conifer litter with shrub understory. Spread rate

moderate; flame length moderate.

b. Humid climate. Extinction moisture content is 30 percent.

i. TU2 Fuelbed is moderate litter load with shrub component. Spread rate

moderate; flame length low.

ii. TU3 Fuelbed is moderate litter load with grass and shrub components.

Spread rate high; flame length moderate.

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

a. Fuelbed is recently burned but able to carry wildland fire.

i. TL1 Light to moderate load, fuels 1 to 2 inches deep. Spread rate very low;

flame length very low.

b. Fuelbed not recently burned.

i. Fuelbed composed of broadleaf (hardwood) litter.

1. TL2 Low load, compact. Spread rate very low; flame length very low.

2. TL6 Moderate load, less compact. Spread rate moderate; flame

length low.

3. TL9 Very high load, fluffy. Spread rate moderate; flame length

moderate.

ii. Fuelbed composed of long-needle pine litter.

1. TL8 moderate load and compactness may include small amount of

herbaceous load. Spread rate moderate; flame length low.

iii. Fuelbed not composed broadleaf or long-needle pine litter.

1. Fuelbed includes both fine and coarse fuels.

a. TL4 Moderate load, includes small diameter downed logs.

Spread rate low; flame length low.

b. TL7 Heavy load, includes larger diameter downed logs. Spread

rate low; flame length low.

2. Fuelbed does not include coarse fuels.

a. TL3 Moderate load conifer litter. Spread rate very low; flame

length low.
12 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

b. TL5 High load conifer litter; light slash or mortality fuel. Spread

rate low; flame length low.

c. TL9 Very high load broadleaf litter; heavy needle-drape in

otherwise sparse shrub layer. Spread rate moderate; flame length

moderate.

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

a. Fuelbed is activity fuel.

i. SB1 Fine fuel load is 10 to 20 tons/acre, weighted toward fuels 1 to 3 inches

diameter class, depth is less than 1 foot. Spread rate moderate; flame length

low.

ii. SB2 Fine fuel load is 7 to 12 tons/acre, evenly distributed across 0 to 0.25,

0.25 to 1, and 1 to 3 inch diameter classes, depth is about 1 foot. Spread rate

moderate; flame length moderate.

iii. SB3 Fine fuel load is 7 to 12 tons/acre, weighted toward 0 to 0.25 inch

diameter class, depth is more than 1 foot. Spread rate high; flame length

high.

b. Fuelbed is blowdown.

i. SB2 Blowdown is scattered, with many trees still standing. Spread rate

moderate; flame length moderate.

ii. SB3 Blowdown is moderate, trees compacted to near the ground. Spread

rate high; flame length high.

iii. SB4 Blowdown is total, fuelbed not compacted, foliage still attached.

Spread rate very high; flame length very high.

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

a. NB1 Urban or suburban development; insufficient wildland fuel to carry

wildland fire.

b. NB2 Snow/ice.

c. NB3 Agricultural field, maintained in nonburnable condition.

d. NB8 Open water.

e. NB9 Bare ground.

Fuel Model Crosswalks

These crosswalks will help users of the original 13 fuel models make the transition to

using the new set. For each of the 13 original fuel models we suggest one or more fuel

models from the new set to consider. However, you are not limited to these choices;

always use the fuel model that provides the best fit for fire behavior prediction.

The crosswalks use adjective classes to compare spread rate and flame length between

the original fuel models and their related models from the new set (table 6).

Note: We computed the relative change in fire behavior between original and new

models using 5 miles/hour midflame wind speed, low dead fuel moisture, two-thirds

cured herbaceous fuels, and low live woody fuels (moisture scenario D2L2). Relative

change among fuel models might be different for different environmental conditions; use

these crosswalks as a guide only.

There is a crosswalk table for each major fire-carrying fuel type of the original 13 fuel

models. The crosswalk uses adjective classes to compare spread rate and flame length

between the original 13 fuel models and their related models from the new set.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 13

Grass fuel type

Consider using one ... if you used one of these models from the original set.

of these fuel models 1 2 3

from the new set... Short Grass Timber Grass and Understory Tall Grass

GR1 For very sparse or heavily

grazed grass; for lower

spread rate and flame length

GR2 For slightly lower spread For comparable spread rate

rate and comparable and slightly lower flame length

flame length

GR3 For lower spread rate and

slightly lower flame length

GR4 For slightly lower spread For higher spread rate and

rate and much higher slightly higher flame length

flame length

GR5 For lower spread rate and

slightly lower flame length

GR6 For slightly lower spread rate

and comparable flame length

GR7 For comparable spread For much higher spread For comparable spread rate

rate and significantly rate and flame length and slightly higher flame length

higher flame length

GR8 For comparable spread rate

and higher flame length

GR9 For higher spread rate and

much higher flame length

GS1 For slightly lower spread

rate and lower flame length

GS2 For slightly lower spread

rate and flame length

Note: All grass fuel models from the new set are dynamic fuel models, which means that herbaceous load is transferred between live and dead

categories according to live herbaceous moisture content. Original models 1 and 3 have only a dead component. Original fuel model 2 has a

live herbaceous component but is static. Exact fire behavior comparisons between original and new grass models can only be made when live

herbaceous moisture content is 30 percent or less. These comparisons were made with a live herbaceous moisture content of 60 percent (twothirds cured).

Table 6—Adjective class definitions for fire behavior comparisons.

Relative change in fire behavior

Adjective class (percent change from original model)

Comparable 0-15

Slightly higher/lower 15-50

Higher/lower 50-100

Much higher/lower 100-200

Significantly higher/lower 200+
14 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

Shrub fuel type

Consider using one ... if you used one of these models from the original set.

of these fuel models 4 5 6 7

from the new set... Chaparral Brush Dormant Brush Southern Rough

SH1 For lower spread rate For lower spread rate

and flame length and flame length

SH2 For lower spread rate For lower spread rate

and slightly lower and flame length

flame length

SH3 For lower spread rate

and flame length

SH4 For slightly lower spread For comparable spread

rate and comparable rate and flame length

flame length

SH5 For slightly lower For much higher

spread rate and spread rate and

flame length flame length

SH6 For slightly lower For slightly lower

spreadrate and spread rate and

higher flame length higher flame length

SH7 For slightly lower For slightly higher

spread rate and spread rate and much

flame length higher flame length

SH8 For slightly lower

spread rate and

higher flame length

SH9 For slightly higher

spread rate and much

higher flame length

TU5 For lower spread rate

and slightly higher

flame length

GS2 For comparable spread

rate and slightly lower

flame length; with grass

component
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 15

Timber fuel type

Consider using one ... if you used one of these models from the original set.

of these fuel models 8 9 10

from the new set... Compact Timber Litter Hardwood Litter Timber (Understory)

TL1 For lower spread rate and

slightly lower flame length

TL2 For lower spread rate and

flame length

TL3 For comparable spread

rate and flame length

TL4 For slightly higher spread

rate and flame length

TL5 For much higher spread

rate and higher flame length

TL6 For slightly lower spread rate

and comparable flame length

TL7 For slightly higher spread

rate and higher flame length

TL8 For slightly lower spread rate

and slightly higher flame length

TL9 For comparable spread rate

and higher flame length

TU1 For higher spread rate For lower spread rate and

and flame length flame length

TU2 For slightly higher spread rate

and slightly lower flame length;

high extinction moisture

TU3 For much higher spread rate

and slightly higher flame length;

high extinction moisture

TU4 For slightly higher spread rate

and comparable flame length

TU5 For comparable spread rate

and slightly higher flame length

SH2 For lower spread rate and

flame length
16 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

Slash fuel type

Consider using one ... if you used one of these models from the original set.

of these fuel models 11 12 13

from the new set... Light Logging Slash Medium Logging Slash Heavy Logging Slash

TL5 For slightly lower spread rate

and flame length

SB1 For comparable spread rate For lower spread rate and flame

and flame length length

SB2 For much higher spread rate For comparable spread rate and For comparable spread rate

and higher flame length slightly lower flame length and slightly lower flame length

SB3 For much higher spread rate and For higher spread rate and

comparable flame length comparable flame length

SB4 For significantly higher spread

rate and slightly higher flame

length
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 17

Fuel Models ______________________________________________________

In this section we list the fuel model parameters and describe each fuel model and

fuel type.

Fuel Model Parameters

Parameters of the new fuel models include load by class and component, surface-areato-volume (SAV) ratio by class and component, fuel model type (static or dynamic),

fuelbed depth, extinction moisture content, and fuel particle heat content (table 7). Fuel

inputs not listed are constant for the entire set: 10-hr dead fuel SAV ratio is 109 1/ft, and

100-hr SAV ratio is 30 1/ft. Total fuel particle mineral content is 5.55 percent; effective

(silica-free) mineral content is 1.00 percent. Ovendry fuel particle density is 32 lb/ft3.

Fuel Type Page

A fuel type page consists of a brief description of the fuel type followed by a pair of

charts depicting predicted fire behavior over a range of midflame wind speeds, one for

headfire spread rate and one for headfire flame length. These charts are for moisture

scenario D2L2 (low dead fuel moisture, two-thirds cured live herbaceous, low live

woody fuel moisture). The moisture contents by class and category are:

Dead 1-hr 6 percent

Dead 10-hr 7

Dead 100-hr 8

Live herbaceous 60 (2/3 cured)

Live woody 90

Use the charts to compare the relative behavior of the various models within a fuel

type, but be aware that the relative behavior may be different at other moisture contents.

Fuel models with herbaceous load are sensitive to live herbaceous moisture content.

The herbaceous fuel in moisture scenario D2L2 is two-thirds cured, which means that 67

percent of the herbaceous load is actually at the dead 1-hr moisture content, while the

remaining 33 percent retains the 60 percent moisture content.
18 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

Table 7—Fuel model parameters.

Fuel Dead fuel

Fuel Fuel load (t/ac) Fuel SAV ratio (1/ft)b bed extinction Heat

model Live Live model Dead Live Live depth moisture content

code 1-hr 10-hr 100-hr herb woody typea 1-hr herb woody (ft) (percent) BTU/lb)c

GR1 0.10 0.00 0.00 0.30 0.00 dynamic 2200 2000 9999 0.4 15 8000

GR2 0.10 0.00 0.00 1.00 0.00 dynamic 2000 1800 9999 1.0 15 8000

GR3 0.10 0.40 0.00 1.50 0.00 dynamic 1500 1300 9999 2.0 30 8000

GR4 0.25 0.00 0.00 1.90 0.00 dynamic 2000 1800 9999 2.0 15 8000

GR5 0.40 0.00 0.00 2.50 0.00 dynamic 1800 1600 9999 1.5 40 8000

GR6 0.10 0.00 0.00 3.40 0.00 dynamic 2200 2000 9999 1.5 40 9000

GR7 1.00 0.00 0.00 5.40 0.00 dynamic 2000 1800 9999 3.0 15 8000

GR8 0.50 1.00 0.00 7.30 0.00 dynamic 1500 1300 9999 4.0 30 8000

GR9 1.00 1.00 0.00 9.00 0.00 dynamic 1800 1600 9999 5.0 40 8000

GS1 0.20 0.00 0.00 0.50 0.65 dynamic 2000 1800 1800 0.9 15 8000

GS2 0.50 0.50 0.00 0.60 1.00 dynamic 2000 1800 1800 1.5 15 8000

GS3 0.30 0.25 0.00 1.45 1.25 dynamic 1800 1600 1600 1.8 40 8000

GS4 1.90 0.30 0.10 3.40 7.10 dynamic 1800 1600 1600 2.1 40 8000

SH1 0.25 0.25 0.00 0.15 1.30 dynamic 2000 1800 1600 1.0 15 8000

SH2 1.35 2.40 0.75 0.00 3.85 N/A 2000 9999 1600 1.0 15 8000

SH3 0.45 3.00 0.00 0.00 6.20 N/A 1600 9999 1400 2.4 40 8000

SH4 0.85 1.15 0.20 0.00 2.55 N/A 2000 1800 1600 3.0 30 8000

SH5 3.60 2.10 0.00 0.00 2.90 N/A 750 9999 1600 6.0 15 8000

SH6 2.90 1.45 0.00 0.00 1.40 N/A 750 9999 1600 2.0 30 8000

SH7 3.50 5.30 2.20 0.00 3.40 N/A 750 9999 1600 6.0 15 8000

SH8 2.05 3.40 0.85 0.00 4.35 N/A 750 9999 1600 3.0 40 8000

SH9 4.50 2.45 0.00 1.55 7.00 dynamic 750 1800 1500 4.4 40 8000

TU1 0.20 0.90 1.50 0.20 0.90 dynamic 2000 1800 1600 0.6 20 8000

TU2 0.95 1.80 1.25 0.00 0.20 N/A 2000 9999 1600 1.0 30 8000

TU3 1.10 0.15 0.25 0.65 1.10 dynamic 1800 1600 1400 1.3 30 8000

TU4 4.50 0.00 0.00 0.00 2.00 N/A 2300 9999 2000 0.5 12 8000

TU5 4.00 4.00 3.00 0.00 3.00 N/A 1500 9999 750 1.0 25 8000

TL1 1.00 2.20 3.60 0.00 0.00 N/A 2000 9999 9999 0.2 30 8000

TL2 1.40 2.30 2.20 0.00 0.00 N/A 2000 9999 9999 0.2 25 8000

TL3 0.50 2.20 2.80 0.00 0.00 N/A 2000 9999 9999 0.3 20 8000

TL4 0.50 1.50 4.20 0.00 0.00 N/A 2000 9999 9999 0.4 25 8000

TL5 1.15 2.50 4.40 0.00 0.00 N/A 2000 9999 1600 0.6 25 8000

TL6 2.40 1.20 1.20 0.00 0.00 N/A 2000 9999 9999 0.3 25 8000

TL7 0.30 1.40 8.10 0.00 0.00 N/A 2000 9999 9999 0.4 25 8000

TL8 5.80 1.40 1.10 0.00 0.00 N/A 1800 9999 9999 0.3 35 8000

TL9 6.65 3.30 4.15 0.00 0.00 N/A 1800 9999 1600 0.6 35 8000

SB1 1.50 3.00 11.00 0.00 0.00 N/A 2000 9999 9999 1.0 25 8000

SB2 4.50 4.25 4.00 0.00 0.00 N/A 2000 9999 9999 1.0 25 8000

SB3 5.50 2.75 3.00 0.00 0.00 N/A 2000 9999 9999 1.2 25 8000

SB4 5.25 3.50 5.25 0.00 0.00 N/A 2000 9999 9999 2.7 25 8000

a

 Fuel model type does not apply to fuel models without live herbaceous load.

b

 The value 9999 was assigned in cases where there is no load in a particular fuel class or category

c

 The same heat content value was applied to both live and dead fuel categories.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 19

Fuel Model Page

A fuel model page consists of:

• The three-part fuel model naming

• A set of three photos

• A brief description of the fuel model

• A summary of computed fuel model characteristics

• A pair of charts depicting fire behavior over a range of midflame wind speeds

Further details follow.

Naming—The fuel model code and number (in parentheses) are displayed on the first

line, followed on the next line by the full fuel model name. The fuel model code is used

for oral and written communication and for input to fire behavior models. The fuel model

number is used internally by some fire behavior models and for mapping applications.

The fuel model name is a brief description of the fuel model.

Photos—Up to three representative photos were selected to illustrate each fuel model.

Conditions other than those illustrated may still be appropriate for the fuel model; use the

photos as a general guide only.

Description—Main characteristics of each fuel model are briefly described.

Summary characteristics—Summary characteristics of each fuel model include fine

fuel load, characteristic surface-area-to-volume ratio (SAV), packing ratio, and extinction moisture content.

Fine fuel load is defined as the dead 1-hr load plus the live herbaceous and live woody loads.

Across the new set of 40 fuel models, fine fuel load ranges from 0.30 to 13.05 tons/acre.

Characteristic SAV is the average SAV across all fuel classes and categories,

weighted by the surface area within each class and category. Characteristic SAV ranges

from 1,144 to 2,216 1/ft in this new set of fuel models.

Packing ratio is the fraction of fuelbed volume that is occupied by fuel particles, a

function of fuel load, fuelbed depth, and fuel particle density. In this fuel model set,

packing ratio varies from 0.00143 to 0.04878 (dimensionless).

Extinction moisture content is the weighted average dead fuel moisture content at

which the fire spread model predicts spread will not take place. More important, the

amount by which the extinction moisture content exceeds the actual determines (in part)

fire behavior. Thus, for a given dead fuel moisture content, predicted fire spread increases

with increasing extinction moisture content.

Fire behavior charts—A pair of charts depicts predicted fire behavior (spread rate

and flame length) for each fuel model over a range of midflame wind speeds. All

predictions use live moisture scenario L2 (60 percent live herbaceous moisture content,

90 percent live woody), which corresponds to a two-thirds cured herbaceous fuelbed.

The four lines on each chart refer to dead fuel moisture scenarios (table 3).

Nonburnable Fuel Type Models (NB)

The nonburnable “fuel models” are included on the next five pages to provide

consistency in how the nonburnable portions of the landscape are displayed on a fuel

model map. In all NB fuel models there is no fuel load—wildland fire will not spread.
20 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

NB1 (91)

Urban/Developed

Description: Fuel model NB1 consists of land covered by urban and suburban

development. To be called NB1, the area under consideration must not support

wildland fire spread. In some cases, areas mapped as NB1 may experience

structural fire losses during a wildland fire incident; however, structure ignition in

those cases is either house-to-house or by firebrands, neither of which is directly

modeled using fire behavior fuel models. If sufficient fuel vegetation surrounds

structures such that wildland fire spread is possible, then choose a fuel model

appropriate for the wildland vegetation rather than NB1.

Expected fire behavior:

No fire spread
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 21

NB2 (92)

Snow/Ice

Description: Land covered by permanent snow or ice is included in NB2. Areas

covered by seasonal snow can be mapped to two different fuel models: NB2 for

use when snow-covered and another for use in the fire season.

Expected fire behavior:

No fire spread
22 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

NB3 (93)

Agricultural

Description: Fuel model NB3 is agricultural land maintained in a nonburnable

condition; examples include irrigated annual crops, mowed or tilled orchards, and

so forth. However, there are many agricultural areas that are not kept in a

nonburnable condition. For example, grass is often allowed to grow beneath vines

or orchard trees, and wheat or similar crops are allowed to cure before harvest;

in those cases use a fuel model other than NB3.

Expected fire behavior:

No fire spread
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 23

NB8 (98)

Open Water

Description: Land covered by open bodies of water such as lakes, rivers and

oceans comprises NB8.

Expected fire behavior:

No fire spread
24 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

NB9 (99)

Bare Ground

Description: Land devoid of enough fuel to support wildland fire spread is

covered by fuel model NB9. Such areas may include gravel pits, arid deserts with

little vegetation, sand dunes, rock outcroppings, beaches, and so forth.

Expected fire behavior:

No fire spread
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 25

Grass Fuel Type Models (GR)

The primary carrier of fire in the GR fuel models is grass. Grass fuels can vary from heavily

grazed grass stubble or sparse natural grass to dense grass more than 6 feet tall. Fire behavior

varies from moderate spread rate and low flame length in the sparse grass to extreme spread rate

and flame length in the tall grass models.

All GR fuel models are dynamic, meaning that their live herbaceous fuel load shifts from live to

dead as a function of live herbaceous moisture content. The effect of live herbaceous moisture

content on spread rate and intensity is strong.
26 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

GR1 (101)

Short, Sparse Dry Climate Grass (Dynamic)

Description: The primary carrier of fire in GR1 is sparse grass, though small amounts

of fine dead fuel may be present. The grass in GR1 is generally short, either naturally

or by grazing, and may be sparse or discontinuous. The moisture of extinction of GR1

is indicative of a dry climate fuelbed, but GR1 may also be applied in high-extinction

moisture fuelbeds because in both cases predicted spread rate and flame length are

low compared to other GR models.

Fine fuel load (t/ac) 0.40

Characteristic SAV (ft-1) 2054

Packing ratio (dimensionless) 0.00143

Extinction moisture content (percent) 15
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 27

GR2 (102)

Low Load, Dry Climate Grass (Dynamic)

Description: The primary carrier of fire in GR2 is grass, though small amounts of

fine dead fuel may be present. Load is greater than GR1, and fuelbed may be more

continuous. Shrubs, if present, do not affect fire behavior.

Fine fuel load (t/ac) 1.10

Characteristic SAV (ft-1) 1820

Packing ratio (dimensionless) 0.00158

Extinction moisture content (percent) 15
28 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

GR3 (103)

Low Load, Very Coarse, Humid Climate Grass (Dynamic)

Description: The primary carrier of fire in GR3 is continuous, coarse, humid-climate

grass. Grass and herb fuel load is relatively light; fuelbed depth is about 2 feet.

Shrubs are not present in significant quantity to affect fire behavior.

Fine fuel load (t/ac) 1.60

Characteristic SAV (ft-1) 1290

Packing ratio (dimensionless) 0.00143

Extinction moisture content (percent) 30
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 29

GR4 (104)

Moderate Load, Dry Climate Grass (Dynamic)

Description: The primary carrier of fire in GR4 is continuous, dry-climate grass.

Load and depth are greater than GR2; fuelbed depth is about 2 feet.

Fine fuel load (t/ac) 2.15

Characteristic SAV (ft-1) 1826

Packing ratio (dimensionless) 0.00154

Extinction moisture content (percent) 15
30 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

GR5 (105)

Low Load, Humid Climate Grass (Dynamic)

Description: The primary carrier of fire in GR5 is humid-climate grass. Load is

greater than GR3 but depth is lower, about 1 to 2 feet.

Fine fuel load (t/ac) 2.9

Characteristic SAV (ft-1) 1631

Packing ratio (dimensionless) 0.00277

Extinction moisture content (percent) 40
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 31

GR6 (106)

Moderate Load, Humid Climate Grass (Dynamic)

Description: The primary carrier of fire in GR6 is continuous humid-climate grass.

Load is greater than GR5 but depth is about the same. Grass is less coarse than GR5.

Fine fuel load (t/ac) 3.5

Characteristic SAV (ft-1) 2006

Packing ratio (dimensionless) 0.00335

Extinction moisture content (percent) 40
32 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

GR7 (107)

High Load, Dry Climate Grass (Dynamic)

Description: The primary carrier of fire in GR7 is continuous dry-climate

grass. Load and depth are greater than GR4. Grass is about 3 feet tall.

Fine fuel load (t/ac) 6.4

Characteristic SAV (ft-1) 1834

Packing ratio (dimensionless) 0.00306

Extinction moisture content (percent) 15
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 33

GR8 (108)

High Load, Very Coarse, Humid Climate Grass (Dynamic)

Description: The primary carrier of fire in GR8 is continuous, very coarse, humidclimate grass. Load and depth are greater than GR6. Spread rate and flame length

can be extreme if grass is fully cured.

Fine fuel load (t/ac) 7.8

Characteristic SAV (ft-1) 1302

Packing ratio (dimensionless) 0.00316

Extinction moisture content (percent) 30
34 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

GR9 (109)

Very High Load, Humid Climate Grass (Dynamic)

Description: The primary carrier of fire in GR9 is dense, tall, humid-climate

grass. Load and depth are greater than GR8, about 6 feet tall. Spread rate

and flame length can be extreme if grass is fully or mostly cured.

Fine fuel load (t/ac) 10.0

Characteristic SAV (ft-1) 1612

Packing ratio (dimensionless) 0.00316

Extinction moisture content (percent) 40
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 35

Grass-Shrub Fuel Type Models (GS)

The primary carrier of fire in the GS fuel models is grass and shrubs combined;

both components are important in determining fire behavior.

All GS fuel models are dynamic, meaning that their live herbaceous fuel load shifts

from live to dead as a function of live herbaceous moisture content. The effect of live

herbaceous moisture content on spread rate and intensity is strong and depends on the

relative amount of grass and shrub load in the fuel model.
36 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

GS1 (121)

Low Load, Dry Climate Grass-Shrub (Dynamic)

Description: The primary carrier of fire in GS1 is grass and shrubs combined.

Shrubs are about 1 foot high, grass load is low. Spread rate is moderate;

flame length low. Moisture of extinction is low.

Fine fuel load (t/ac) 1.35

Characteristic SAV (ft-1) 1832

Packing ratio (dimensionless) 0.00215

Extinction moisture content (percent) 15
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 37

GS2 (122)

Moderate Load, Dry Climate Grass-Shrub (Dynamic)

Description: The primary carrier of fire in GS2 is grass and shrubs combined.

Shrubs are 1 to 3 feet high, grass load is moderate. Spread rate is high; flame

length moderate. Moisture of extinction is low.

Fine fuel load (t/ac) 2.1

Characteristic SAV (ft-1) 1827

Packing ratio (dimensionless) 0.00249

Extinction moisture content (percent) 15
38 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

GS3 (123)

Moderate Load, Humid Climate Grass-Shrub (Dynamic)

Description: The primary carrier of fire in GS3 is grass and shrubs combined.

Moderate grass/shrub load, average grass/shrub depth less than 2 feet. Spread rate

is high; flame length moderate. Moisture of extinction is high.

Fine fuel load (t/ac) 3.0

Characteristic SAV (ft-1) 1614

Packing ratio (dimensionless) 0.00259

Extinction moisture content (percent) 40
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 39

GS4 (124)

High Load, Humid Climate Grass-Shrub (Dynamic)

Description: The primary carrier of fire in GS4 is grass and shrubs combined. Heavy

grass/shrub load, depth greater than 2 feet. Spread rate high; flame length very high.

Moisture of extinction is high.

Fine fuel load (t/ac) 12.4

Characteristic SAV (ft-1) 1674

Packing ratio (dimensionless) 0.00874

Extinction moisture content (percent) 40
40 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

Shrub Fuel Type Models (SH)

The primary carrier of fire in the SH fuel models is live and dead shrub twigs

and foliage in combination with dead and down shrub litter. A small amount of

herbaceous fuel may be present, especially in SH1 and SH9, which are dynamic

models (their live herbaceous fuel load shifts from live to dead as a function of live

herbaceous moisture content). The effect of live herbaceous moisture content on

spread rate and flame length can be strong in those dynamic SH models.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 41

SH1 (141)

Low Load Dry Climate Shrub (Dynamic)

Description: The primary carrier of fire in SH1 is woody shrubs and shrub

litter. Low shrub fuel load, fuelbed depth about 1 foot; some grass may be

present. Spread rate is very low; flame length very low.

Fine fuel load (t/ac) 1.7

Characteristic SAV (ft-1) 1674

Packing ratio (dimensionless) 0.00280

Extinction moisture content (percent) 15
42 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

SH2 (142)

Moderate Load Dry Climate Shrub

Description: The primary carrier of fire in SH2 is woody shrubs and shrub litter.

Moderate fuel load (higher than SH1), depth about 1 foot, no grass fuel present.

Spread rate is low; flame length low.

Fine fuel load (t/ac) 5.2

Characteristic SAV (ft-1) 1672

Packing ratio (dimensionless) 0.01198

Extinction moisture content (percent) 15
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 43

SH3 (143)

Moderate Load, Humid Climate Shrub

Description: The primary carrier of fire in SH3 is woody shrubs and shrub litter.

Moderate shrub load, possibly with pine overstory or herbaceous fuel, fuel bed depth

2 to 3 feet. Spread rate is low; flame length low.

Fine fuel load (t/ac) 6.65

Characteristic SAV (ft-1) 1371

Packing ratio (dimensionless) 0.00577

Extinction moisture content (percent) 40
44 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

SH4 (144)

Low Load, Humid Climate Timber-Shrub

Description: The primary carrier of fire in SH4 is woody shrubs and shrub litter.

Low to moderate shrub and litter load, possibly with pine overstory, fuel bed depth

about 3 feet. Spread rate is high; flame length moderate.

Fine fuel load (t/ac) 3.4

Characteristic SAV (ft-1) 1682

Packing ratio (dimensionless) 0.00227

Extinction moisture content (percent) 30
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 45

SH5 (145)

High Load, Dry Climate Shrub

Description: The primary carrier of fire in SH5 is woody shrubs and shrub

litter. Heavy shrub load, depth 4-6 feet. Spread rate very high; flame length

very high. Moisture of extinction is high.

Fine fuel load (t/ac) 6.5

Characteristic SAV (ft-1) 1252

Packing ratio (dimensionless) 0.00206

Extinction moisture content (percent) 15
46 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

SH6 (146)

Low Load, Humid Climate Shrub

Description: The primary carrier of fire in SH6 is woody shrubs and shrub

litter. Dense shrubs, little or no herbaceous fuel, fuelbed depth about 2 feet.

Spread rate is high; flame length high.

Fine fuel load (t/ac) 4.3

Characteristic SAV (ft-1) 1144

Packing ratio (dimensionless) 0.00412

Extinction moisture content (percent) 30
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 47

SH7 (147)

Very High Load, Dry Climate Shrub

Description: The primary carrier of fire in SH7 is woody shrubs and shrub

litter. Very heavy shrub load, depth 4 to 6 feet. Spread rate lower than SH7,

but flame length similar. Spread rate is high; flame length very high.

Fine fuel load (t/ac) 6.9

Characteristic SAV (ft-1) 1233

Packing ratio (dimensionless) 0.00344

Extinction moisture content (percent) 15
48 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

SH8 (148)

High Load, Humid Climate Shrub

Description: The primary carrier of fire in SH8 is woody shrubs and shrub litter. Dense

shrubs, little or no herbaceous fuel, fuelbed depth about 3 feet. Spread rate is high; flame

length high.

Fine fuel load (t/ac) 6.4

Characteristic SAV (ft-1) 1386

Packing ratio (dimensionless) 0.00509

Extinction moisture content (percent) 40
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 49

SH9 (149)

Very High Load, Humid Climate Shrub (Dynamic)

Description: The primary carrier of fire in SH9 is woody shrubs and shrub litter.

Dense, finely branched shrubs with significant fine dead fuel, about 4 to 6 feet tall;

some herbaceous fuel may be present. Spread rate is high, flame length very high.

Fine fuel load (t/ac) 13.05

Characteristic SAV (ft-1) 1378

Packing ratio (dimensionless) 0.00505

Extinction moisture content (percent) 40
50 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

Timber-Understory Fuel Type Models (TU)

The primary carrier of fire in the TU fuel models is forest litter in combination

with herbaceous or shrub fuels. TU1 and TU3 contain live herbaceous load and are

dynamic, meaning that their live herbaceous fuel load is allocated between live

and dead as a function of live herbaceous moisture content. The effect of live

herbaceous moisture content on spread rate and intensity is strong and depends

on the relative amount of grass and shrub load in the fuel model.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 51

TU1 (161)

Low Load Dry Climate Timber-Grass-Shrub (Dynamic)

Description: The primary carrier of fire in TU1 is low load of grass and/or

shrub with litter. Spread rate is low; flame length low.

Fine fuel load (t/ac) 1.3

Characteristic SAV (ft-1) 1606

Packing ratio (dimensionless) 0.00885

Extinction moisture content (percent) 20
52 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

TU2 (162)

Moderate Load, Humid Climate Timber-Shrub

Description: The primary carrier of fire in TU2 is moderate litter load with

shrub component. High extinction moisture. Spread rate is moderate; flame

length low.

Fine fuel load (t/ac) 1.15

Characteristic SAV (ft-1) 1767

Packing ratio (dimensionless) 0.00603

Extinction moisture content (percent) 30
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 53

TU3 (163)

Moderate Load, Humid Climate Timber-Grass-Shrub (Dynamic)

Description: The primary carrier of fire in TU3 is moderate forest litter with grass and

shrub components. Extinction moisture is high. Spread rate is high; flame length

moderate.

Fine fuel load (t/ac) 2.85

Characteristic SAV (ft-1) 1611

Packing ratio (dimensionless) 0.00359

Extinction moisture content (percent) 30
54 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

TU4 (164)

Dwarf Conifer With Understory

Description: The primary carrier of fire in TU4 is short conifer trees with grass or

moss understory. Spread rate is moderate; flame length moderate.

Fine fuel load (t/ac) 6.5

Characteristic SAV (ft-1) 2216

Packing ratio (dimensionless) 0.01865

Extinction moisture content (percent) 12
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 55

TU5 (165)

Very High Load, Dry Climate Timber-Shrub

Description: The primary carrier of fire in TU5 is heavy forest litter with a shrub or

small tree understory. Spread rate is moderate; flame length moderate.

Fine fuel load (t/ac) 7.0

Characteristic SAV (ft-1) 1224

Packing ratio (dimensionless) 0.02009

Extinction moisture content (percent) 25
56 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

Timber Litter Fuel Type Models (TL)

The primary carrier of fire in the TL fuel models is dead and down woody fuel. Live

fuel, if present, has little effect on fire behavior.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 57

TL1 (181)

Low Load Compact Conifer Litter

Description: The primary carrier of fire in TL1 is compact forest litter. Light

to moderate load, fuels 1 to 2 inches deep. May be used to represent a

recently burned forest. Spread rate is very low; flame length very low.

Fine fuel load (t/ac) 1.0

Characteristic SAV (ft-1) 1716

Packing ratio (dimensionless) 0.04878

Extinction moisture content (percent) 30
58 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

TL2 (182)

Low Load Broadleaf Litter

Description: The primary carrier of fire in TL2 is broadleaf (hardwood) litter. Low

load, compact broadleaf litter. Spread rate is very low; flame length very low.

Fine fuel load (t/ac) 1.4

Characteristic SAV (ft-1) 1806

Packing ratio (dimensionless) 0.04232

Extinction moisture content (percent) 25
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 59

TL3 (183)

Moderate Load Conifer Litter

Description: The primary carrier of fire in TL3 is moderate load conifer litter,

light load of coarse fuels. Spread rate is very low; flame length low.

Fine fuel load (t/ac) 0.50

Characteristic SAV (ft-1) 1532

Packing ratio (dimensionless) 0.02630

Extinction moisture content (percent) 20
60 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

TL4 (184)

Small downed logs

Description: The primary carrier of fire in TL4 is moderate load of fine litter and coarse

fuels. Includes small diameter downed logs. Spread rate is low; flame length low.

Fine fuel load (t/ac) 0.50

Characteristic SAV (ft-1) 1568

Packing ratio (dimensionless) 0.02224

Extinction moisture content (percent) 25
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 61

TL5 (185)

High Load Conifer Litter

Description: The primary carrier of fire in TL5 is high load conifer litter; light slash

or mortality fuel. Spread rate is low; flame length low.

Fine fuel load (t/ac) 1.15

Characteristic SAV (ft-1) 1713

Packing ratio (dimensionless) 0.01925

Extinction moisture content (percent) 25
62 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

TL6 (186)

Moderate Load Broadleaf Litter

Description: The primary carrier of fire in TL6 is moderate load broadleaf litter,

less compact than TL2. Spread rate is moderate; flame length low.

Fine fuel load (t/ac) 2.4

Characteristic SAV (ft-1) 1936

Packing ratio (dimensionless) 0.02296

Extinction moisture content (percent) 25
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 63

TL7 (187)

Large Downed Logs

Description: The primary carrier of fire in TL7 is heavy load forest litter, includes

larger diameter downed logs. Spread rate low; flame length low.

Fine fuel load (t/ac) 0.30

Characteristic SAV (ft-1) 1229

Packing ratio (dimensionless) 0.03515

Extinction moisture content (percent) 25
64 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

TL8 (188)

Long-Needle Litter

Description: The primary carrier of fire in TL8 is moderate load long-needle pine litter,

may include small amount of herbaceous load. Spread rate is moderate; flame length

low.

Fine fuel load (t/ac) 5.8

Characteristic SAV (ft-1) 1770

Packing ratio (dimensionless) 0.03969

Extinction moisture content (percent) 35
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 65

TL9 (189)

Very High Load Broadleaf Litter

Description: The primary carrier of fire in TL9 is very high load, fluffy broadleaf

litter. TL9 can also be used to represent heavy needle-drape. Spread rate is

moderate; flame length moderate.

Fine fuel load (t/ac) 6.65

Characteristic SAV (ft-1) 1733

Packing ratio (dimensionless) 0.03372

Extinction moisture content (percent) 35
66 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

Slash-Blowdown Fuel Type Models (SB)

The primary carrier of fire in the SB fuel models is activity fuel or blowdown.

Forested areas with heavy mortality may be modeled with SB fuel models.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 67

SB1 (201)

Low Load Activity Fuel

Description: The primary carrier of fire in SB1 is light dead and down activity fuel.

Fine fuel load is 10 to 20 t/ac, weighted toward fuels 1 to 3 inches diameter class,

depth is less than 1 foot. Spread rate is moderate; flame length low.

Fine fuel load (t/ac) 1.50

Characteristic SAV (ft-1) 1653

Packing ratio (dimensionless) 0.02224

Extinction moisture content (percent) 25
68 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

SB2 (202)

Moderate Load Activity Fuel or Low Load Blowdown

Description: The primary carrier of fire in SB2 is moderate dead and down activity

fuel or light blowdown. Fine fuel load is 7 to 12 t/ac, evenly distributed across 0 to

0.25, 0.25 to 1, and 1 to 3 inch diameter classes, depth is about 1 foot. Blowdown is

scattered, with many trees still standing. Spread rate is moderate; flame length

moderate.

Fine fuel load (t/ac) 4.5

Characteristic SAV (ft-1) 1884

Packing ratio (dimensionless) 0.01829

Extinction moisture content (percent) 25
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 69

SB3 (203)

High Load Activity Fuel or Moderate Load Blowdown

Description: The primary carrier of fire in SB3 is heavy dead and down activity fuel

or moderate blowdown. Fine fuel load is 7 to 12 t/ac, weighted toward 0 to 0.25 inch

diameter class, depth is more than 1 foot. Blowdown is moderate, trees compacted to

near the ground. Spread rate is high; flame length high.

Fine fuel load (t/ac) 5.50

Characteristic SAV (ft-1) 1935

Packing ratio (dimensionless) 0.01345

Extinction moisture content (percent) 25
70 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005

SB4 (204)

High Load Blowdown

Description: The primary carrier of fire in SB4 is heavy blowdown fuel. Blowdown is

total, fuelbed not compacted, most foliage and fine fuel still attached to blowdown.

Spread rate very high; flame length very high.

Fine fuel load (t/ac) 5.25

Characteristic SAV (ft-1) 1907

Packing ratio (dimensionless) 0.00744

Extinction moisture content (percent) 25
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-153. 2005 71

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subsystem. Gen. Tech. Rep. INT-167. Ogden, UT: U.S. Department of Agriculture, Forest Service,

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red and white pine, Northern tallgrass prairie, and mixed oak types in the Central and Lake States. PMS

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pine, pocosin, and marshgrass types in the Southeast United States. PMS 835. Boise, ID: National Wildfire

Coordinating Group, National Interagency Fire Center. 56 p.

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with supplemental sites for Volume VI. PMS 838. Boise, ID: National Wildfire Coordinating Group,

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