1. Crown Fire Methods LaWen Hollingsworth Rocky Mountain Research Station Fire Modeling Institute Missoula, MT Sharing Fire Behavior Practices and Lessons Learned November 16, 2015

2. Background ModelFinney (1998) Scott and Reinhardt (2001) Surface fire spread Rothermel (1972) Crown fire initiation Van Wagner (1977) Crown fire spread Rothermel (1991) Spotting Albini (1979) Two crown fire methods: Finney (1998) Scott and Reinhardt (2001) Both methods available in: WFDSS – STFB, NTFB, FSPro Stand-alone Systems – FlamMap, FARSITE

4. = SURFACE FIRE

6. = PASSIVE CROWN FIRE

7. = ACTIVE CROWN FIRE

8. Type of Fire Fireline intensity Flame length Spotting HPASpread rate Surface R surface Byram (1959) None Passive Surface + some crown R surface (Finney) or R crown (S/R) Thomas (1963) Yes Active Surface + some crown R crown Thomas (1963) Yes Summary by Type of Fire

9. R crown = actual crown fire spread rate R surface = surface rate of spread (Rothermel 1972) CFB = crown fraction burned R active = active crown fire spread rate (Rothermel 1991) R crown = R surface + CFB ( R active – R surface ) Crown Fire Spread Rate

10. CFB C rown F raction B urned – weighted average of surface and crown fire spread rates proportion of trees involved in the crowning phase 0 1.0 Crown Fraction Burned Finney method Scott and Reinhardt method

11. Important Considerations For the analyst, holding all modeling components equal: When using Scott & Reinhardt (2001), passive crown fire spread rate can vary greatly between the surface fire spread rate and the potential crown fire spread rate, depending on the fire environment. When using Finney (1998), passive crown fire spread rate will be the same as surface fire rate of spread. HOWEVER, passive crown fires loft embers so overall fire growth will be greater than surface fire.

12. Spotting

13. Canopy cover Crown fraction burned < 0.50.5 – 0.8> 0.8 < 50% 123 50 – 80% 236 > 80% 3610 CC and CFB are used to calculate the number of torching trees (which influences firebrand lofting height) Finney method S&R method

14. Spotting from Torching Trees

15. Important Considerations In STFB and NTFB in WFDSS, spotting default = 0.00% Spotting is stochastic in STFB, NTFB, and FSPro Spotting only occurs when passive or active crown fire is modeled More embers are lofted at finer landscape resolutions in STFB and FSPro For an individual fire, a larger predicted size will encounter more nodes  therefore more embers are launched

16. laurahamilton.theworldrace.org Same But Different

17. SAMEDIFFERENT Threshold between surface fire and some type of crown fire ( critical surface intensity ) Finney method lower crown fire spread rate lower crown fireline intensity lower crown flame length Proportion of surface fire versus some type of crown fire Scott and Reinhardt Faster ROS for passive crown fire Faster ROS for active crown fire Generally speaking, Active crown fire (Finney) ≈ Active crown fire (S&R) Scott and Reinhardt Larger overall fire growth for passive crown fire Larger overall fire growth for active crown fire

18. Selecting a Crown Fire Method Finney method

19. Selecting a Crown Fire Method Finney method Scott and Reinhardt method www.reddit.com

20. Selecting a Crown Fire Method Finney method Scott and Reinhardt method

21. References Albini, F.A. 1979. Spot fire distance from burning trees—a predictive model. Gen. Tech. Rep. INT-56. Ogden, UT: USDA Forest Service, Intermountain Forest and Range Experiment Station. Alexander, M. E. 1988. Help with making crown fire hazard assessments. In: Fischer, W. C.; Arno, S. F., comps. Protecting people and homes from wildfire in the Interior West: proceedings of the Symposium and Workshop; 1988 October 6-8; Missoula, MT. Proc. Gen. Tech. Rep. INT-251. Ogden, UT: USDA Forest Service, Intermountain Forest and Range Experimental Station. pp. 147- 156. Byram, G. M. 1959. Combustion of forest fuels. In: Forest fire: Control and use, 2 nd edition. New York, NY: McGraw-Hill: chapter 1, 61-89. Finney, M. A. 1998. FARSITE: Fire Area Simulator—model development and evaluation. Res. Pap. RMRS-RP-4. Ft. Collins, CO: USDA Forest Service, Rocky Mountain Research Station. 47 p. Finney, M.A. 2004 FARSITE: Fire Area Simulator—model development and evaluation. Res. Pap. RMRS-RP-4 Revised. Ft. Collins, CO: USDA Forest Service, Rocky Mountain Research Station. 52 p. Rothermel, R. C. 1972. A mathematical model for predicting fire spread in wildland fuels. Res. Pap. INT-115. Ogden, UT: USDA Forest Service, Intermountain Forest and Range Experiment Station. 40 p. Rothermel, R. C. 1991. Predicting behavior and size of crown fires in the Northern Rocky Mountains. Res. Pap. INT-438. Ogden, UT: USDA Forest Service, Intermountain Forest and Range Experiment Station. 46 p. Scott, Joe H.; Reinhardt, Elizabeth D. 2001. Assessing crown fire potential by linking models of surface and crown fire behavior. Res. Pap. RMRS-RP-29. Fort Collins, CO: USDA Forest Service, Rocky Mountain Research Station. 59 p. Thomas, P. H. 1963. Size of flames from natural fires. In: Proceedings of the Ninth Symposium on Combustion. 1962. New York, NY: Academic Press. pp. 844-859. Van Wagner, C. E. 1977. Conditions for the start and spread of crown fire. Canadian Journal of Forest Research 7: 23-34.

22. Questions and Comments