Search Fire Behavior Field Reference Guide, PMS 437

Text (indexed):
  1. Map Scale & Map Distance
  2. Slope Estimation
  3. Unit Conversions
  4. Average Latitude for Each State
  5. Declination

Map Scale & Map Distance

The map scale is printed in the map legend. It is given as a ratio of inches on the map corresponding to inches, feet, or miles on the ground. For example, a map scale indicating a ratio of 1: 24,000 (in/in), means that for every 1 inch on the map, 24,000 inches have been covered on the ground. Ground distances on maps are usually given in feet or miles.

ScaleRep. fractionMap (in/mi)Map (in/ch)Feet per map inch

Firefighter Math Map Scale; Firefighter Math Spread/Map Distance

Slope Estimation

Slope (Degrees)Slope (Percent)

Standard LANDFIRE slope themes are represented in units of degrees (°). Many locally produced landscapes over the year’s stored slopes in percent (%). It is much easier to estimate slope in percent, estimating the elevation change and the horizontal distance and calculating the ratio. BehavePlus, and BEHAVE tools before that, default to slope input in percent.

Firefighter Math Slope Percent and Slope Angle

To convert from slope in degrees (°) to slope in percent (%), a scientific calculator is needed.

  1. Enter the slope in degrees.
  2. Press the Tangent button.
  3. Multiply the result by 100 to get slope in percent.

Unit Conversions

Online and downloadable apps are available from Apple (OSX & IOS), Google Play (Android), and MS Windows for making unit conversions for distance, temperature, area, volume, weight, time, energy and other items.

Metric UnitMultiply byEnglish UnitMultiply byMetric Unit

Firefighter Math Conversions reference provides several tables and conversion factors for the user.

Average Latitude for Each State

StateAverage Latitude
New Hampshire44
New Jersey40
New Mexico34
New York43
North Carolina35
North Dakota47
Rhode Island41
South Carolina34
South Dakota44
West Virginia38


Global Reference


US/UK World Magnetic Model - Epoch 2015.0 Main Field Declination (D)

(East Declination in Red, West in Blue; subtract from true compass reading)

recent map of magnetic declination for field navigation.


Text (indexed):
  1. Map Datum
  2. Map Projections & Coordinate Systems
  3. Re-projecting Shapefile or arcgrid in ArcGIS
  4. ArcGIS Web Services

Map Datum

Some common datum, or Global Coordinate Systems (GCS), used in North America include:

  • North American Datum of 1927 (NAD27): Local datum well suited to the United States, Canada, Mexico, and the Caribbean. Uses the Clarke 1866 spheroid.
  • North American Datum of 1983 (NAD83): An earth-centered datum that corrects NAD27 coordinates based on both earth and satellite measurements. Uses the GRS 1980 spheroid. Coordinates are very like WGS84 coordinates and can be used interchangeably with them.
  • World Geodetic System of 1984 (WGS84): Earth-centered datum common for datasets with a global extent. Uses the WGS84 spheroid. This is the datum that GPS coordinates are based on.

Geographic Transformations Between Different Datum

ArcGIS gives us a warning if we attempt to add data to our map that have a different GCS, or datum. For example, if we have one layer depicting the 40 fire behavior fuel models. As with projection on-the-fly, the data frame’s GCS defaults to that of the first layer added to the map, which is NAD83. If we then try to add a fire perimeter shapefile with the WGS84 geographic coordinate system, we get a warning that a geographic transformation may be necessary.

A geographic transformation, sometimes referred to as a datum transformation, is a set of mathematical formulas for converting coordinates from one datum to another. At this point, you may specify the transformation by clicking the transformations box in the warning dialog box. In most cases, the transformation at the top of the list will be the best choice.

Map Projections and Coordinate Systems

A projected coordinate system (PCS) can reference the same geographic locations using a Cartesian system, which includes a uniform, linear unit of measure.

  • Universal Transverse Mercator (UTM) divides the earth into 60 zones, each six degrees of latitude wide. The figure below depicts a simplified view of UTM zones covering the continental United States.

Universal Transverse Mercator (UTM) projection zones for the Continental United States.

  • State Plane Coordinate Systems are a good example of a PCS being independent of its map projection. Lambert Conformal Conic projections are used for domains with greater east-west extent, Transverse Mercator projections are used for domains with greater north-south extent. Some use an oblique Mercator projection.

Projected Coordinate Systems. This graphic demonstrates how different projections project portions of a round globe onto a flat map surface.

  • LANDFIRE uses the Albers Equal Area Conic projection for national level data products because it is well suited for data with an east-west orientation at middle latitudes, such as the continental United States. Furthermore, because this is an equal area projection, all areas on the map are proportional to the same areas on the earth.
  • WFDSS (Wildland Fire Decision Support System) Custom Albers Projection is an Albers Equal Area Conic projection that is defined based upon the WFDSS incident spatial domain. In that sense, each incident and its associated fire behavior analyses will have a unique WFDSS Custom Albers projection, By using a custom projection for each incident, centered on that incident, reduces the distortion inherent in all projections in the area around the fire. Among other factors, the custom projection reduces the potential for errors in direction (wind direction, aspect, etc.) that could otherwise be introduced if a non-custom projection were used.

Within the WFDSS incident, landscape (lcp) files created for fire behavior analyses are stored in its Custom Albers projection and can only be downloaded in that projection. Other fire behavior outputs can be downloaded in either the WFDSS Custom Albers projection or in a geographic coordinate system.

The WFDSS Custom Albers projection is recognized by ArcGIS, and datasets stored in a WFDSS Custom Albers projection can be used in ArcMap like any other dataset.

Re-projecting Shapefile or Arcgrid in ArcGIS

If a shapefile or ascii grid will not display as an overlay on a landscape (lcp) in FARSITE or FLAMMAP, it cannot be used by those systems. It is most likely using a different coordinate system than the lcp does.

In this case, the file (feature/shapefile or raster/ascii grid) can be re-projected to the same coordinate system so it can be displayed onscreen and used in reference by the landscape editor in FARSITE.

ArcToolbox Menu - Data Management

  1. Open a new ArcMap window and add the shapefile or raster file that is stored in the desired projection. By adding the shapefile (or grid) with the desired projection first, the coordinate system of the Data Frame will default to the desired projection.
  2. Next, add the shapefile that is stored in the other projection.
  3. If the ArcToolbox window is not already displayed, click on the ArcToolbox icon to show the ArcToolbox window.
  4. In the ArcToolbox window, click on the plus sign next to Data Management Tools to expand the selection. Next, click on the plus sign next to Projections and Transformations to expand the selection. Next, click on the plus sign next to Feature (for shapefiles or Raster (for grids) to expand the selection. Double-click on Project to open the tool.
  5. In the Project window, under Input Dataset or Feature Class, select the shapefile/raster grid that is currently stored with the wrong projection. The Input Coordinate System should automatically default to its projection. If none is displayed, that means that there is no prj file accompanying it. If the projection is known, it can be specified here.
  6. Specify an output shapefile or raster grid under Output Dataset or Feature Class. Click on the button next to Output Coordinate System. In the Spatial Reference Properties window that pops up, click on the Import button. Navigate to and select the shapefile that is stored in the desired coordinate system. The new projection properties will load into the Spatial Reference Properties window. Click OK on the Spatial Reference Properties window.
  7. Click OK in the Project window to create a new shapefile that is stored in the chosen UTM projection.

If the user discovers the feature or raster does not have a defined projection; one can be added by selecting Define Projection, found under Projections and Transformations.

ArcGIS Web Services

While traditional use of GIS software has depended on stand-alone datasets, increasingly, much of end-user application is moving rapidly to online resources.  

  • ESRI ArcGIS Online (AGOL) provides password protected access to agency, interagency, and public content.  There is a NIFC online site that provides a home for many fire management applications.  Request access here.
  • ESRI Collector is the companion application that  extends visualization and data collection to the field on mobile devices. The ability to take maps in the field on mobile devices, with and without cell service, makes this technology very useful for many different incident response positions.  Same login used for AGOL applies here.  
  • There is a growing number of web mapping services that can be accessed from their published server over the internet.  Look for protocols like Web Mapping Service (WMS) and REST Service to access data without having to download and store it.
Text (indexed):

Set up before going to the field

  • Make sure fresh batteries are loaded and extra sets available.
  • Transfer background maps for the area using MapSource (if available).
  • Turn unit on to initialize and acquire satellites ahead of time if you are in a new area or haven’t used the unit in at least a week. This may take as long as 20 minutes in the open, away from buildings, canopy, and obstructions.
  • Download and clear old waypoints and tracks from memory.
  • Turn off Active Track log. Set it to the preferred Collection method (Time is best) and an appropriate logging rate for the data collection. Five seconds works for most walking collection. Keep in mind the total storage of the GPS.
  • Ensure Simulator Mode is not ON when collecting data.
  • Set unit time zone and date (Ensure Daylight Savings Time if needed).
  • Check Interface Protocol is set properly.
  • Set the Coordinate System (UTM or LAT/LONG) & Datum to ensure compatibility with written coordinates you may need to navigate to or Map.
  • Set Heading to magnetic or true. If true, ensure same declination is used.

Field – GPS Data Collection

  • Hold GPS antenna away from body with antenna up. Better yet, hold at, or above the head. Purchase an external antenna to free hands if needed or for better reception in vehicles.
  • Mark the waypoints for point locations at beginning and ending of track log collections. Writing down a position is just backup.
  • Most GPS units will collect data no matter what the GPS quality is. It’s up to you to monitor the GPS Satellite Page for anomalies and accuracy.
  • Collect when 3D GPS is shown. Do not collect data in 2D unless necessary.


  • Collect all waypoints in Averaged Position mode if you are standing still, when possible, and if your receiver has that capability. Minimum of 10 positions, maximum of 20 minutes. Somewhere in between is enough to generate a quality position in most cases.
  • Collect an instantaneous waypoint only when moving or in a hurry, or if using the eTrex line.
  • Edit default waypoint numbers to letters or words that are more descriptive, or make good field notes to ensure you remember what features are represented by which numbers.

Track logs

  • Use Stop when Full or Fill Record Mode rather than wrap to prevent overwriting track log points when Active Track log becomes full.
  • Turn on Active Track log at start location and immediately begin moving.
  • Stop Active Track log when movement is stopped or mission is finished.
  • Always Stop Active Track just shy of starting point when collecting an area (polygon). Overlapping makes conversion to GIS more challenging.
  • Use caution when saving an Active Track log. Garmin will generalize active track to save space, thereby degrading data.


Text (indexed):

Table of Contents for This Page

  1. Available Tools and Resources
  2. Required Surface Model Inputs
  3. Surface Model Outputs
  4. Acceleration Effect on Rate of Spread

This comprehensive worksheet can be used with the surface fire behavior lookup tables, the Nomograms and Nomographs, as well as BehavePlus, and runs if you want a paper copy.

Consider using this as your briefing documentation by including a weather forecast narrative, your thoughts about recent fire activity, your sense of how accurate the predictions seem, and when you expect changes through the burn period.

Worksheet for recording information collected and estimates produced when estimating surface fire behavior.

Available Tools and Resources

This section describes how to estimate expected surface fire behavior and provides several references tools used in the process:

  1. A Worksheet (above) designed to document a complete assessment for surface fire behavior and growth using either the lookup tables or the nomographs.
  2. EWS Tables for estimating Effective Windspeed from Slope and Midflame Windspeed. The Effective Windspeeds that result from these tables assumes that wind is blowing ± 30° from upslope. For other situations, manual vectoring using the EWS Table would be necessary.
  3. Surface Fire Behavior Lookup Tables for making estimates of surface fire spread and flame length. Note these assumptions:
    • 10-hr and 100-hr moisture values of 6% and 8% are used in the lookup tables.
    • The *20ft/FCST wind line is provided as a convenience, but only works with stated Wind Adjustment Factor (WAF) & no slope adjustments.
    • Backing & flanking columns are only rough estimates based on ½ and 1 mph windspeeds. Use the Flanking and Backing Fire Behavior Nomograph , or BehavePlus for more precise estimates.
  4. Instructions for Surface Fire Behavior Nomographs and Nomograms.
  5. Flanking and Backing Fire Behavior Nomograph for estimating rate of spread and flame length where fire is spreading more slowly on the flanks and at the back of the fire perimeter.

These tools can help you make expected surface fire behavior estimates. Consider the following:

Required Surface Model Inputs

Surface Model Outputs

  • Rate of Spread is useful in fireline tactical applications; identifying what is at risk in the burn period, escape route limitations.
  • Flame Length/Fireline Intensity is used generally in determining what tactics make sense during the peak burn period, interpreting safety zone concerns, and suggesting spotting potential.
  • Heat per Unit Area is available from nomograms and BehavePlus. Like the Energy Release Component, it may be helpful in suggesting burn duration and fire effects.

Acceleration Effect on Rate of Spread

Fire Spread Acceleration. Fire spread accelerates over a period of time after initiation. The period of time varies based on the fuelbed.

Fire acceleration is defined as the rate of increase in fire spread rate. It affects the amount of time required for a fire spread rate to achieve the theoretical steady state spread rate given 1) its existing spread rate, and 2) constant environmental conditions.

Because initiating fires can take 20 minutes to over an hour to reach a steady spread rate, fire behavior and fire growth can be significantly reduced in the first burn period, and when beginning to spread in subsequent periods.

At this time, fire acceleration is implemented only in FARSITE, using the model developed for the Canadian Forest Fire Behavior Prediction System (Alexander et. al. 1992).

It is active by default, but can be turned off as a model input.

As implemented, inputs are segregated by type of Ignition (point vs. line source) and potentially by fuel type (grass, shrub, timber, slash, a default, or by fuel model). Grass fuels are expected to have more rapid acceleration rates (shorter time to reach equilibrium) than fuel types with larger woody material (slash, etc.).

Text (indexed):
  1. Online Data Sources
  2. Desktop Applications
  3. Google Earth Pro
  4. Mobile Applications

Online Data Sources

In addition to the following national sources, inquire about local GIS resource availability.

Desktop Applications

Google EarthPro


Viewing 3D Terrain in Google Earth Pro requires selecting the terrain option from the bottom of the layers portion of the left side menu.


Mobile Applications

Collector for ArcGIS

Collector works on iOS, Android, and Windows 10 and allows the user to collect and update information in the field, take maps and data offline, sync changes when connected, attribute data collection with easy-to-use map-driven forms, and capture and share photos and videos.

Avenza Maps and Pro Subscriptions

Avenza Maps is GIS technology available on Apple, Android, and Windows devices for navigation, information collection, and sharing geographic information and knowledge. It displays geospatial PDF, GeoPDF® and GeoTIFF and interacts with the GPS on the device, allowing the user to record GPS tracks, add placemarks, and find places.

Avenza Maps Pro users will be able to import and export shapefiles and current capabilities of the Avenza PDF Maps App in terms of data collection and editing but with Avenza Maps Pro, shapefiles are a supported import/export format. More features will be added, over time. It is a subscription service, requiring registration of individual devices. 

With the release of the Pro version, the current standard Avenza PDF Maps App will be changing, the most significant change will be users may only access five maps at any time on their device, unless the maps have all been obtained from the Avenza Map Store. It is strongly recommended that all users upgrade to the new Avenza Maps Pro version.

Avenza Maps Pro may be available under an enterprise license contract through the U.S. Forest Service.

Other Products

  • Gaia GPS and GaiaPro - Gaia GPS integrates topo maps, offline navigation tools, and planning features, seamlessly across phones, tablets, and GaiaPro spans Gaia GPS on iOS, and Android. GaiaPro is an upgrade to the standard application, including custom maps, premium satellite imagery, public land, hunting zones, and tools including layered maps, area measurement, and printing.
  • You Need a Map - A map that works in Apple IOS to provide coverage of the US without a cell phone signal, showing not just roads but also terrain, streams, lakes, and other landmarks.
  • Theodolite 
Text (indexed):

EWS integrates the effect of winds and slope on a surface fire behavior estimate based on the fuel model the fire is expected to be burning in. These tables produce the resulting EWS when winds are blowing upslope.

For downslope and cross-slope winds, use the zero (0) mph row in the Midflame Windspeed (MFWS) column to estimate the Slope Equivalent Windspeed. It can be used as the MFWS in the lookup tables to produce slope vector fire behavior estimates for use in the Vectoring Fire Behavior section.

Effective Windspeed Adjustment Table. Use this series of tables to estimate windspeed when wind is blowing upslope. Factors include midflame windspeed, and slope. Using a midflame windspeed of zero (0) and the appropriate slope will allow user to estimate the slope equivalent windspeed.



Text (indexed):
  1. Grass Fuel Models
  2. Grass/Shrub Fuel Models
  3. Brush, or Shrub, Fuel Models
  4. Timber Litter Fuel Models
  5. Timber Understory Fuel Models
  6. Slash/Blowdown Fuel Models

Grass Fuel Models

Fuel Model 1 (Short Grass – 1 ft)

Fire spread is governed by the fine, very porous, and continuous herbaceous fuels that have cured or are nearly cured. Fires are surface fires that move rapidly through the cured grass and associated material. Very little shrub or timber is present, generally less than 1/3 of the area. Grasslands and savanna are represented along with stubble, grass-tundra, and grass-shrub combinations that met the above area constraint. Annual and perennial grasses are included in this fuel model.

Fuel Model 1, Short Grass spread and flame length lookup tables.

Fuel Model 3 (Tall Grass – 2.5 ft)

Fires in this fuel are the most intense of the grass group and display high rates of spread under the influence of wind. Wind may drive fire into the upper heights of the grass and across standing water. Stands are tall, averaging about 3 feet (1 m), but considerable variation may occur. Approximately 1/3 or more of the stand is considered dead or cured and maintains the fire. Wild or cultivated grains that have not been harvested can be considered similar to tall prairie and marshland grasses.

 Fuel Model 3, Tall Grass spread and flame length lookup tables.

Grass/Shrub Fuel Models

Fuel Model 2 (Timber – Grass and Understory)

Fire spread is primarily through the fine herbaceous fuels, either curing or dead. These are surface fires where the herbaceous material, as well as litter and dead/down stemwood from the open shrub or timber overstory, contribute to the fire intensity. Open shrub lands and pine stands or scrub oak stands that cover one-third to two-thirds of the area may generally fit this model. Such stands may include clumps of fuels that generate higher intensities and that may produce firebrands. Some pinyon-juniper included here.

 Fuel Model 2, Timber – Grass and Understory spread and flame length lookup tables.

Brush, or Shrub, Fuel Models

Fuel Model 4 (Chaparral – 6 ft)

Intense and fast-spreading fires involve the foliage, and live and dead fine, woody material in the crowns of a nearly continuous secondary overstory. Stands of mature shrubs, 6 or more feet tall, such as California mixed chaparral, the high pocosin along the east coast, the pine barrens of New Jersey, or the closed jack pine stands of the north-central States are typical candidates. Besides flammable foliage, dead woody material in the stands significantly contributes to the fire intensity. The height of stands qualifying for this model depends on local conditions. A deep litter layer may also hamper suppression efforts.

 Fuel Model 4, Chaparral spread and flame length lookup tables.

Fuel Model 5 (Brush – 2 ft)

Fire is generally carried in the surface fuels that are made up of litter cast by the shrubs and grasses, or forbs in the understory. The fires are generally not very intense because surface fuel loads are light, the shrubs are young with little dead material, and the foliage contains little volatile material. Usually shrubs are short and almost totally cover the area. Young, green stands with no dead wood would qualify: laurel, vine maple, alder, or even chaparral, manzanita, or chamise.

 Fuel Model 5, Brush spread and flame length lookup tables.

Fuel Model 6 (Dormant Brush, Hardwood Slash)

Fires carry through the shrub layer where the foliage is more flammable than fuel model 5, but this requires moderate winds, greater than 8 mi/h (13 km/h) at midflame height. Fire will drop to the ground at low wind speeds or at openings in the stand. The shrubs are older. A broad range of shrub conditions is covered by this model. Fuel situations to be considered include intermediate stands of chamise, chaparral, oak brush, low pocosin, Alaskan spruce taiga, and shrub tundra. Even hardwood slash that has cured can be considered. Pinyon-juniper shrublands may be represented but may over-predict rate of spread except at high winds.

 Fuel Model 6, Dormant Brush, Hardwood Slash spread and flame length lookup tables.

Fuel Model 7 (Southern Rough)

Fires burn through the surface and shrub strata with equal ease and can occur at higher dead fuel moisture contents because of the flammability of live foliage and other live material. Stands of shrubs are generally between 2 and 6 feet (0.6 and 1.8 m) high. Palmetto-Gallberry understory-pine overstory sites are typical and low pocosins may be represented. Black spruce-shrub combinations in Alaska may also be represented.

 Fuel Model 7, Southern Rough spread and flame length lookup tables.

Timber Litter Fuel Models

Fuel Model 8 (Closed Timber Litter)

Slow-burning ground fires with low flame lengths are generally the case, although the fire may encounter an occasional “jackpot” or heavy fuel concentration that can flare up. Only under severe weather conditions involving high temperatures, low humidities, and high winds do the fuels pose fire hazards. Closed canopy stands of short-needle conifers or hardwoods that have leafed out support fire in the compact litter layer. This layer is mainly needles, leaves, and occasionally twigs because little undergrowth is present in the stand. Representative conifer types are white pine, and lodgepole pine, spruce, fir, and larch.

 Fuel Model 8, Closed Timber Litter spread and flame length lookup tables.

Fuel Model 9 (Hardwood Litter)

Fires run through the surface litter faster than model 8 and have longer flame height. Both long-needle conifer stands and hardwood stands, especially the oak-hickory types, are typical. Fall fires in hardwoods are predictable, but high winds will cause higher rates of spread than predicted because of spotting caused by rolling and blowing leaves. Closed stands of long-needled pine like ponderosa, Jeffrey, and red pines, or southern pine plantations are grouped in this model. Concentrations of dead-down woody material will contribute to possible torching of trees, spotting, and crowning.

 Fuel Model 9, Hardwood Litter spread and flame length lookup tables.

Timber Understory Fuel Models

Fuel Model 10 (Timber – Litter and Understory)

The fires burn in the surface and ground fuels with greater fire intensity than the other timber litter models. Dead-down fuels include greater quantities of 3-inch (7.6-cm) or larger Iimbwood resulting from overmaturity or natural events that create a large load of dead material on the forest floor. Crowning out, spotting, and torching of individual trees are more frequent in this fuel situation, leading to potential fire control difficulties. Any forest type may be considered if heavy down material is present; examples are insect- or disease-ridden stands, windthrown stands, overmature situations with deadfall, and aged light thinning or partial-cut slash.

 Fuel Model 10, Timber – Litter and Understory spread and flame length lookup tables.

Slash/Blowdown Fuel Models

Fuel Model 11 (Light Logging Slash)

Fires are fairly active in the slash and herbaceous material intermixed with the slash. The spacing of the rather light fuel load, shading from overstory, or the aging of the fine fuels can contribute to limiting the fire potential. Light partial cuts or thinning operations in mixed conifer stands, hardwood stands, and southern pine harvests are considered. Clearcut operations generally produce more slash than represented here. The less-than-3-inch (7.6 cm) material load is less than 12 tons per acre (5.4 t/ha). The greater-than-3-inch (7.6-cm) is represented by not more than 10 pieces, 4 inches (10.2 cm) in diameter, along a 50-foot (15 m) transect.

 Fuel Model 11, Light Logging Slash spread and flame length lookup tables.

Fuel Model 12 (Medium Logging Slash)

Rapidly spreading fires with high intensities capable of generating firebrands can occur. When fire starts, it is generally sustained until a fuel break or change in fuels is encountered. The visual impression is dominated by slash and much of it is less than 3 inches (7.6 cm) in diameter. The fuels total less than 35 tons per acre (15.6 t/ha) and seem well distributed. Heavily thinned conifer stands, clearcuts, and medium or heavy partial cuts are represented. The material larger than 3 inches (7.6 cm) is represented by encountering 11 pieces, 6 inches (15.2 cm) in diameter, along a 50-foot (15 m) transect.

 Fuel Model 12, Medium Logging Slash spread and flame length lookup tables.

Fuel Model 13 (Heavy Logging Slash)

Fire is generally carried across the area by a continuous layer of slash. Large quantities of heavy fuels are present. Fires spread quickly through the fine fuels and intensity builds up more slowly as the large fuels start burning. Active flaming supports a wide variety of firebrands, contributing to spotting problems. The total load may exceed 200 tons per acre (89.2 t/ha), but fine fuels are generally only 10 percent of the total load. Situations where the slash still has “red” needles attached but the total load is lighter can be represented because of the earlier high intensity and quicker area involvement.

 Fuel Model 13, Heavy Logging Slash spread and flame length lookup tables.

Text (indexed):
  1. Instructions for Nomograph Use (Scott 2007)
  2. Instructions for Nomogram Use (Rothermel 1983)

Instructions for Nomograph Use (Scott 2007)

Reference: Scott, Joe H. 2007. Nomographs for estimating surface fire behavior characteristics. Gen. Tech. Rep. RMRS-GTR-192. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 119 p

Each fuel model includes a duplicate set of effective windspeed protractor and fire behavior nomograph, one for low windspeeds and one for high windspeeds. Select the one with applicable windspeeds.

Example Nomograph

Example Nomograph. Updated in 2007 to include versions for all 53 models.

Inputs Required:

  1. Fuel Model.
  2. Midflame Windspeed and direction, azimuth clockwise from upslope.
  3. Slope percent.
  4. Dead and Live Fuel Moistures.

Determine Effective Windspeed (EWS) - Low or High

Use the left side nomograph, shown above, if the situation includes cross slope winds.

  1. Plot the slope vector (a) in the upslope direction to the hash representing the slope percent. Interpolate if necessary.
  2. Plot the wind vector (b) using the concentric circle to for the input windspeed and the azimuth above for direction.
  3. Plot parallel vectors (c and d) and resultant vector (e). Read resulting windspeed (e) and direction (f).

Estimate Head Fire Rate of Spread and Flame Length

If the fuel model includes a live fuel component, use the nomograph that references the appropriate live fuel moisture. Otherwise, there is only one nomograph, shown on right.

  1. Using the input dead fuel moisture, draw vertical line (g) to the estimated EWS curve.
  2. Read the flame length from the embedded curves at the intersection (j). Interpolate between lines if necessary.
  3. Draw horizontal line (h) to the left axis and read the Rate of Spread at intersection (i).

Instructions for Nomogram Use (Rothermel 1983)

Reference: Rothermel, Richard C. How to predict the spread and intensity of forest and range fires. Gen. Tech. Rep. INT-143. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest, and Range Experiment Station; 1983. 1 61 p. 

Download Nomograms Here 

Unlike the newer nomographs, the original surface fire behavior nomograms have several limitations:

  • These nomograms are only available for the original 13 fuel models.
  • They are intended for use with wind blowing within ±30 degrees of upslope. Use in vectoring is possible, though it is not outlined here.

Inputs Required

  1. Fuel model.
  2. Midflame windspeed.
  3. Percent slope.
  4. Dead fuel moisture (use 1-hr).
  5. Live fuel moisture for fuel models 2, 4, 5, 7, & 10.

Select the Appropriate Windspeed (Low/High) Nomogram

The numbered steps below correspond to the labeled lines on the example nomograms.

Part I: Estimate Effective Windspeed (For All Fuel Models)

  1. In the lower left quadrant, draw a vertical line from percent slope value to intersect midflame windspeed curve. Draw a horizontal line to the left axis and read effective windspeed.
  2. In the lower right quadrant, identify and highlight the appropriate effective windspeed line. Interpolate by adding a line for effective windspeed from step1 above if it is between existing lines.

Part II: Fuel Moisture

For FM 1, 3, 6, 8, 9, 11, 12, 13 with only dead fuel.

  1. In the upper left quadrant of the nomogram, identify and highlight the appropriate dead fuel moisture line based on the input value provided. Interpolate by drawing a new line between existing lines if necessary.

For FM 2, 4, 5, 7, 10 with live fuel.

  • Using the two upper quadrants, locate the appropriate dead fuel moisture value on the two outer vertical axes (highlighted). Connect with a horizontal line.
  • Connect the point where the horizontal line intersects the live fuel curve in the upper left quadrant to the origin point, creating a straight line.
  • Using the input live fuel moisture provided, identify and highlight the appropriate S-curve in the upper right quadrant. Interpolate by adding a new line between existing lines if necessary.

At this point, turning lines have been identified in all 4 quadrants (including the S-curve in the upper right quadrant and the default corner to corner line in the lower left). The nomogram is prepared for Part III.

Part III: Estimating Fire Behavior

With the preparations in parts I and II, turning lines have been highlighted in the lower right quadrant and the upper left quadrant, as well as the appropriate S-curve in the upper right quadrant for fuel models with live fuels.

  • Begin in the upper right quadrant. Draw a horizontal line from dead fuel moisture to the highlighted fuel moisture turning line (s-curve).
  • From the intersection, draw a vertical line down to the turning line in the lower right quadrant (highlighted in step 2).
  1. From the intersection with the turning line in the lower right, draw a horizontal line to the turning line in the lower left quadrant.
  2. From the intersection with the turning line in the lower left quadrant, draw a vertical line up to the turning line in the upper left quadrant (highlighted in step 3).
  3. From the intersection with the turning line in the upper left quadrant, draw a horizontal line to the right until it intersects the vertical line drawn in step 4.

Part IV: Reading Fire Behavior Outputs

Read Heat Per Unit Area where the vertical line from step 2 intersects its axis in the upper right quadrant.

  • In the first example (Dead Fuel Only), the Heat Per Unit Area is estimated at approximately 750 BTU/sq. ft.
  • In the second example (Dead & Live Fuels), the Heat Per Unit Area is estimated at approximately 215 BTU/sq. ft.

Read Rate of Spread where the horizontal line from step 5 intersects its axis in the upper right quadrant.

  • In the first example (Dead Fuel Only), the Rate of Spread is estimated at approximately 7 chains per hour.
  • In the second example (Dead & Live Fuels), the Rate of Spread is also estimated at approximately 7 chains per hour.

Read Flame Length and Fireline Intensity at the final intersection produced in step 5.

  • In the first example (Dead Fuel Only), the intersection between lines 4 and 7 comes between the Flame Length/Fireline Intensity contour lines 3/60 and 4/100. It could be estimated as 4 ft or 90 BTU/ft/sec.
  • In the second example (Dead & Live Fuels), the intersection between lines 4 and 7 comes between the Flame Length/Fireline Intensity contour lines 2/25 and 3/60. It could be estimated as 2 ft or 30 BTU/ft/sec.

Example Nomogram for Dead Fuel Only (Fuel Models 1, 3, 6, 8, 9, 11, 12, 13)

Example Surface Fire Behavior Nomogram for fuel models with dead fuels only.

Example Nomogram Using Dead & Live Fuels (Fuel Models 2, 4, 5, 7, 100)

Example Surface Fire Behavior Nomogram for fuel models with both live and dead fuels.



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The tables and nomographs produce good estimates of head fire behavior.

This nomograph uses effective windspeed to produce adjustment factors for both spread rate and flame length that can be applied to the head fire behavior outputs.

Backing and Flanking Nomograph: Estimating Flanking and Backing Fire Behavior from Head Fire Estimates. This nomogram requires an estimate of the effective windspeed, from which a fractional multiplier for both flame length and spread rate can be determined for flanking, backing, and flanking portions of the fire.


  1. Begin with the EWS at the base of the right-hand chart, draw a vertical line to intersect desired spread direction and the axis at the top to read the length to breadth ratio.
  2. Draw a horizontal line from the intersection at desired spread direction into and across the left-hand chart to intersect the left axis. Read the fraction from the left axis and apply it to the headfire ROS to obtain the spread rate in the assumed direction.
  3. Draw a vertical line down from where the horizontal line intersected curve in the left-hand chart to the bottom axis. Read the fraction from this bottom axis and apply it to the headfire flame length estimate to obtain the flame length in the spread direction assumed.


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Projecting fire spread with cross slope winds utilizes a vectoring process, where the effect of wind and the effect of slope on Rate of Spread (ROS) may be represented by separate vectors that represent both a magnitude and a direction. The resultant vector represents both a direction and magnitude of maximum spread in that direction.

  1. Slope Vector is drawn directly upslope and estimated by calculating ROS with the estimated slope steepness and Zero (0) windspeed for inputs.
  2. Wind Vector is drawn in the direction of the wind and estimated by calculating ROS with the estimated windspeed and Zero (0) slope.
  3. Maximum Spread Vector can be drawn as shown and measured to determine the resultant ROS and spread direction.

Vectoring Wind and Slope Example - Examples of vector addition to combine the influences of wind and slope on the resulting speed and direction of fire spread.

In example A here, wind is crossing more upslope, resulting in an enhanced maximum ROS.

In example B, wind is crossing more downslope, resulting in a reduced maximum ROS.

With winds blowing downslope (±30°), the difference between the spread rates is the resulting ROS using the direction from the larger vector.

If the vectoring process is completed manually:

  • ROS is determined from the measured maximum spread vector (spread distance) and the time period used to obtain wind and slope vector estimates.
  • Heat Per Unit Area (H/A) is the same for all component vectors.
  • Fireline intensity (FLI) and flame length (FL) can be calculated from ROS and Heat Per Unit Area (HPA) using these calculations.

FLI = (ROS * HPA)/55

FL = .45 * FLI.46