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Fuels: Canopy Fuel Characteristics

  1. Canopy Cover-Percentage or Class
  2. Stand (Canopy)-Height-ft or m
  3. Canopy Base Height-ft or m
  4. Canopy Bulk Density-kg/m3 or lb/ft3

Canopy Cover - Percentage or Class

The forest Canopy Cover (CC) describes the percent cover or cover class of the tree canopy in a stand. Specifically, CC describes the vertical projection of the tree canopy onto an imaginary horizontal surface representing the ground’s surface. Estimate of CC is used in adjustment of 20 feet winds to mid-flame, fuel moisture conditioning, and spotting distance models.

The scale illustrates representative CC percentages and ranges within each cover class.

Image
Canopy Cover classification. This graphic depicts from above views of canopy cover and its effect on wind sheltering/reduction.

For surface fuels sheltered by a forest canopy on flat terrain. (Scott 2007)

Canopy Cover Wind Sheltering
CC ≤ 5% Unsheltered
5% < CC ≤ 10% Partially Sheltered
10% < CC ≤ 15% Partially Sheltered
15% < CC ≤ 30% Fully Sheltered, Open
30% < CC ≤ 50% Fully Sheltered, Open
CC > 50% Fully Sheltered, Closed

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Stand (Canopy) Height-feet (ft) or meters (m)

The Stand or Canopy Height (SH) describes the average height of the top of the vegetated canopy. SH estimates are used in adjustment of 20 feet winds to mid-flame and in spotting distance models.

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Canopy Base Height-ft or m

The forest Canopy Base Height (CBH) describes the average height from the ground to a forest stand's canopy bottom. Specifically, it is the lowest height in a stand at which there is a sufficient amount of forest canopy fuel to propagate fire vertically into the canopy. Using this definition, ladder fuels such as lichen, dead branches, and small trees are incorporated. Estimate of CBH is used in the Crown Fire Initiation model.

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Describing a Forest Canopy. This graphic highlights the way to think about the primary descriptors for crown fire prediction. Crown Bulk Density describes the crown fuel load and distribution. Stand Height describes height of canopy tops. Crown Base height represents the difficulty for surfaces fires to ignite the canopy. And Foliar Moisture content suggest how readily the canopy will burn.

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Canopy Bulk Density-kg/m3 or lb/ft3

The forest Canopy Bulk Density (CBD) describes the density of available canopy fuel in a stand. It is defined as the mass of available canopy fuel per canopy volume unit. Typical units are either kg/m3 (LANDFIRE default) or lb/ft3 (BehavePlus default). CBD estimates are used to determine the threshold spread rate, or surface wind speed, used to determine the likelihood of active crown fire.

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Canopy Bulk Density is a difficult concept to apply to crown fire predictions. This image shows that CBD varies with height above ground.

The following graph, also displayed in the Crown Fire section under Crown Fire Initiation and Propagation, displays the threshold surface 20 feet wind speed or Crowning Index, necessary for producing active crown fire given a specific canopy bulk density.

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Crowning Index. Based on Rothermel crown fire spread model, canopy bulk density can be related to the windspeed required to sustain crown fire.

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NWCG Latest Announcements

2025 NWCG Incident Response Pocket Guide (IRPG), PMS 461, Now Available

Date: February 27, 2025
Contact: Incident Operations Subcommittee

NWCG is excited to announce that the 2025 NWCG Incident Response Pocket Guide (IRPG), PMS 461, is now available. Visit NWCG's website to learn about the major updates and changes in the 2025 version of the IRPG. The NWCG Guia de Respuesta de Incidente de Bolsillo (GRI), PMS 461-ES is available electronically and will be available from Great Basin Cache by early summer 2025.

All hard copy materials, including the IRPG, are ordered through the Great Basin Cache (GBK). Information on the ordering process can be found in the National Fire Equipment System (NFES) Catalog.

References:

2025 IRPG Information 

NWCG Incident Response Pocket Guide (IRPG), PMS 461 

NWCG Guia de Respuesta de Incidente de Bolsillo (GRI), PMS 461-ES 

NWCG NFES Catalog - Part 2: Publications, PMS 449-2 

2025 Professional Reading Program

Date: February 18, 2025
Contact: Wildland Fire Leadership Development Program (WFLDP)

The Wildland Fire Leadership Development Program is announcing the 2025 Professional Reading list! The goal of the annual reading list is to promote the reading and discussion of the books throughout the year.

The five books chosen for this year are: Surf When You Can by Brett Crozier, Man’s Search for Meaning by Viktor E. Frankl, Elephant Company by Vicki Constantine Croke, Simply Managing by Henry Mintzberg, and Chop Wood Carry Water by Joshua Metcalf.

References:

Professional Reading Program

Task Group Volunteers Needed to Update the Property Loss or Damage Report, OF 289

Date: February 5, 2025
Contact: Julie Bennett, Incident Business Committee Chair

The Incident Business Committee (IBC) is requesting volunteers for a new task group to revise the 1981 version of the Property Loss or Damage Report, OF 289 and create an incident replacement job aid. The volunteers may be recruited from within or outside the Geographic Area Incident Business Committees.

References:

IBC Memorandum 25-02

IBC Correspondence

2025 Updates to the NWCG Standards for Wildland Fire Position Qualifications, PMS 310-1

Date: February 4, 2025
Contact: Incident and Position Standards Committee

The NWCG Incident and Position Standards Committee has updated the NWCG Standards for Wildland Fire Position Qualifications, PMS 310-1. 

These updates address changes to incident position names and requirements for qualification, training, and experience. Updates related to the implementation of Complex Incident Management (CIM) are also included.  

The NWCG Wildland Fire Position Qualification Flowchart, PMS 308 has also been updated to reflect the recent changes.

References:

NWCG Standards for Wildland Fire Position Qualifications, PMS 310-1

NWCG Wildland Fire Position Qualification Flowchart, PMS 308

NWCG Memo: 2025-01 January 2025 Updates to the NWCG Standards for Wildland Fire Positions Qualifications, PMS 310-1