Skip to main content

Surface Fire: Flanking and Backing Fire Behavior

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.

Image
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.

Procedure:

  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.

Return to Top

Print PDF

NWCG Latest Announcements

NEW! S-219, Firing Operations (Blended) Now Available

Date: Sept 11, 2025
Questions? Please contact:
Fuels Management Committee 

The S-219, Firing Operations (Blended) course is now available on the Wildland Fire Learning Portal. Developed through the Incident Performance and Training Modernization (IPTM) effort, this training supports individuals working towards Firing Boss, Single Resource (FIRB) incident qualifications.

This blended course combines online and instructor-led training to provide students with the knowledge and skills required to perform the duties of the FIRB, as described in the NWCG Incident Position Standards for Firing Boss, Single Resource, PMS 350-105.

Any changes to qualification pathways will take effect with the next update of the NWCG Standards for Wildland Fire Position Qualifications, PMS 310-1, scheduled for January 2026.

References:

S-219, Firing Operations (Blended)

NWCG Firing Boss, Single Resource Position Page

Wildland Fire Learning Portal

NWCG Committees Observe Suicide Prevention Awareness Week: September 7-13, 2025

Date: Sep 5, 2025
Questions? Please contact:
Mental Health Subcommittee

The NWCG Mental Health Subcommittee (MHSC) and Risk Management Committee (RMC) recognize the unique challenges and demands faced by the wildland fire community. The MHSC and RMC know that we are all stronger together and believe in fostering a culture of support, understanding, and resilience.

Suicide Prevention Awareness encourages us to actively connect with and support each other. For more information that could make a difference for yourself or someone else please review the materials and resources provided for the 2025 Suicide Prevention Awareness Week.

References:

2025 Suicide Prevention Awareness Week Materials and Resources

NEW! Incident Performance and Training Modernization Story Map Now Available

Date: Aug 26, 2025
Questions? Please contact:
National Wildfire Coordinating Group

NWCG is excited to announce the launch of the Incident Performance and Training Modernization (IPTM) Story Map, a new interactive resource that showcases how NWCG is transforming wildland fire training and qualifications through a performance-based system.

Since its launch in 2023, IPTM has made major strides in updating how we manage incident positions:

  • 36 incident positions now have new Incident Position Standards and Next Generation Position Task Books available for field use
  • 6 more incident positions are nearing completion
  • 111 total incident positions are being analyzed through the IPTM initiative

The Story Map guides you through the IPTM process, highlights key accomplishments, and outlines what’s ahead. Whether you are a trainer or a trainee, this tool offers valuable insight into the modernization effort shaping the future of wildland fire training and qualifications.

This effort would not be possible without the contributions of NWCG staff, NWCG committees, and hundreds of subject matter experts across the wildland fire community.

References:

IPTM Story Map

Incident Performance and Training Modernization Webpage

NEW! S-290, Intermediate Wildland Fire Behavior (Blended) Available Now

Date: Aug 15, 2025
Questions? Please contact:
Fire Behavior Subcommittee

NWCG is excited to announce that the S-290, Intermediate Wildland Fire Behavior (Blended) training is now available on the Wildland Fire Learning Portal. S-290 (Blended) training combines online training and instructor-led training components that support individuals working towards any Single Resource Boss or Fire Effects Monitor incident qualifications.

This second course in the series collectively serves to develop fire behavior prediction knowledge and skills, and provides more detailed information on fuels, weather, and topography that affect wildland fire behavior for safety purposes.

Students are required to finish the prerequisite S-190, Introduction to Wildland Fire Behavior, before enrolling in S-290, Intermediate Wildland Fire Behavior (Blended).

References:

S-290, Intermediate Wildland Fire Behavior (Blended)

S-190, Introduction to Wildland Fire Behavior

Wildland Fire Learning Portal