1. Fire Blow-Up Modeling: Implications for Situational Awareness & LCES
Jo Ann Fites
Adaptive Management Services Enterprise Team, USDA Forest Service

2. Overview Importance of fire accelerations in fatality fires
Near misses?
Modeling canyon blow-ups
Test on Rattlesnake fatality fire
What does this mean for situational awareness & LCES?

3. Fire Fatalities & Blow ups
What is common to loop, rattlesnake, south canyon,
Cramer and others?
Numerous fire fatalities from blow-ups
Especially in drainages or canyons or “chimney’s”
Easily recognized but how fast can blow-ups occur?
Does the speed sink in?

4. Modeling Canyon Blow-Ups
Holding your finger near a match
Existing models (e.g. Rothermel based, FARSITE) have average rates of spread
Do not account for acceleration
Do not account for convective entrainment
Viegas canyon blow-up model
Based on laboratory tests
Mathematical landscape application
Tested with rx burn in chaparral
Viegas applied to several fatality fires in US
Future: predicting when blow-ups occur?

5. Rattlesnake Fire - Test
1953 on Mendocino National Forest
15 fatalities
Acceleration in small drainage a key factor
“Sundowner winds a factor”
Applied Viegas model

7. Applying Viegas Model
Using ARC-GIS, existing tools
Applying geometry

8. Viegas model simulation
Assumptions:
winds 3m/s, alpha=

9. Model run with angles

10. Follow the leader or model?
Model is useful but cannot substitute for the computer with slides in their head
(if it will blow-up)

11. Applications What are the implications? LCES How much time do you have
for egress?
What are your triggers?
Chuck Hartley
when fire hits the bottom it is time to
go..not wait and see what happens
But this depends on the situation
Applications

12. Codfish fire Crews going down into canyon or big box?
Spacing of safety zones?
Protection of structures at top?

13. Egress times for hotshots estimated at 45 minutes
Distance out

14. Sz?
13 minutes
45 minutes
Sz?
40 minutes

15. Operations 1) Where might it escape, size of WFSA
-does the box need to be bigger?
2) overall hazard awareness for resources
- improve situational awareness
- not a substitute but some means of a “slide” for inexperienced crews
3) egress:
- info to compare egress time estimates
- setting triggers – go when it is at the bottom no matter what the size of fire
4) spacing of safety zones
Have to rely 1st upon good, experienced leadership & what is going on at the fire (Codfish – Rax – “I told you it would not reach your sensors”
--this tool is supplemental