Fire Technology Transfer NoteNumber - 25 June 2002

A pocket card for predicting fire behaviour in grasslandsunder severe burning conditions1

M.E. Alexander and L.G. Fogarty

1This Fire Technology Transfer Note is based on an oral presentation made by M.E. Alexander at the 2000

International Wildfire Safety Summit sponsored by the International Association of Wildland Fire held in Edmonton,Alberta, October 10-12, 2000, and represents a slightly modified version of the original paper that appeared as pages8-19 in Butler and Shannon (2000).

Abstract

The grassland fire behaviour pocket cardrecently developed for use by wildland and ruralfirefighters in Canada and New Zealand isreviewed. The pocket card offers a practical fieldguide for quickly estimating the near worst casefire behaviour potential in grasslands. At thesame time it reinforces an awareness of the needfor adopting safe work practices whenattempting to contain grass fires in an effort toavoid burnovers and entrapments therebyeliminating firefighter injuries and fatalities.

Introduction

Many firefighters are surprised to learn thattragedy and near-miss incidents occur infairly light fuels, on small fires, or on isolatedsectors of large fires, and that fire behaviouris relatively quiet just before the incident.Most of us believe that the high-intensitycrown fire in timber or heavy brush is whattraps and kills forest firefighters. Yet, withrare exceptions ... most fires are innocent-appearing just before the accidents.

Wilson and Sorenson (1978).

In 1997, a pocket card entitled “A SIMPLE FIELD

GUIDE FOR ESTIMATING THE BEHAVIOUR AND

SUPPRESSION REQUIREMENTS OF FIRES DRIVEN

BY WIND COMING FROM A CONSTANT DIRECTION,IN OPEN, FULLY CURED GRASSLANDS AT LOW

FUEL MOISTURE” (Alexander and Fogarty 1997)

was jointly developed by the Canadian ForestService (CFS) and the New Zealand ForestResearch Institute (Figure 1). This wasfollowed by Fire Technology Transfer NoteNo. 20 by Fogarty and Alexander (1999)describing the derivation and use of theAlexander and Fogarty (1997) grassland firebehaviour pocket card; a copy of thispublication, as well as the French translationcan be downloaded from the CFS fire researchwebsite (see Downloads at http://nofc.cfs.nrcan.gc.ca/fire/frn/).

Why is the Grassland Fire Behaviour PocketCard Needed?

In comparison to free-burning fires occurring inother wildland fuel complexes, fires spreadingthrough grass fuels are far more responsive tochanges in wind and/or slope. This is especiallyso when the grasslands are in a fully cured state(Garvey and Millie 2000), and the fuels arecritically dry due to high air temperatures, lowrelative humidity and a lack of recent wettingrain (Cheney and Sullivan 1997). This hasimportant implications for firefighter safetywith respect to the potential for burn injuries oreven death (Figure 2). Grass fires can movesurprisingly quickly, and so firefighters need tohave a full appreciation and a healthy respectfor this fact as evident by a significant numberof fatalities associated with grassland fires inthe United States (Wilson and Sorenson 1978;

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Figure 1. The (a) front and (b) back sides of the Alexander and Fogarty (1997) grassland fire behaviour pocket card.Actual dimensions are 11.5 x 17.2 cm (4.5 x 6.75 in.).

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Figure 2. The emphasis of the pocket card is onproviding basic fire behaviour information in verysimplistic terms to ensure safe wildland firefightingoperations. Photos from NFPA (1992).

NWCG 1996; NWCG Safety and HealthWorking Team 1997). A major switch in winddirection can cause the relatively quiet flank ofa grass fire to suddenly become a much wideror larger and more vigorous high-intensity“head” from what previously existed. Similarly,any increase in wind speed above the averagevelocity will result in a correspondingescalation in a fire’s overall rate of spread andintensity or flame size.

How Did the Grassland Fire BehaviourPocket Card Come About?

The inspiration for this field guide to predictgrassland fire behaviour under severe burningconditions came about as the result of one ofthe authors (MEA) undertaking an investigationof a burnover incident in grasslands thatoccurred near the town of Anerley,Saskatchewan, Canada, on October 2, 1993(Alexander 1998; ETC and CIFFC 2000). Arural volunteer firefighter eventually died as aresult of the burns he sustained while engagedin firefighting operations on this grass fire.

An initial draft of the grass fire behaviour pocketcard was prepared by the first author (MEA) aspart of the technical review of a case studyinvolving a “near miss” incident occurring on awildfire in grasslands on New Zealand’s NorthIsland in early 1991 (Rasmussen and Fogarty1997). The final version of the pocket card wascompleted by the second author (LGF) and isincluded as an appendix in Rasmussen andFogarty’s (1997) publication.

What is the Purpose of the Grassland FireBehaviour Pocket Card?

The principle intent of the pocket card is toprovide wildland and rural fire suppressionpersonnel with very basic information ongrassland fire behaviour such as forward spreaddistance and fire size (area and perimeter) inrelation to elapsed time since ignition, inaddition to flame front characteristics (Figure1a), in as simple a manner as possible.However, at the same time it stresses theimportance of adhering to traditional safe workpractices and fire suppression strategies/tactics(Figures 3 and 4).

Figure 3. The pocket card explicitly states that the onlysafe fire suppression strategy/tactic is direct attackflanking action starting from the rear of the fire whilebeing ever mindful of the possibility for rekindling, thevalue of a “black line”, and the necessity for preparing amineralized fireguard.

Figure 4. Safe work practices when engaged in grasslandfire suppression include “anchor and flank” and “onefoot in the green, one foot in the black”. Photo fromNWCG (1990).

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The release of the 1996 California Division ofForestry video “A Firefighter’s Return From aBurnover: the Kelly York Story” (Anon. 1997)has reinforced the need for such a reminder inthe form of a handy aid or guide like thegrassland fire behaviour pocket card. Theconcept of “making a stand” (Fogarty 1996) ata road, firebreak or other narrow barrier to firespread (Figure 5) is certainly not recommendedbecause of the potential for disastrousconsequences, such as demonstrated by themajor burn injuries sustained to a wildlandfirefighter on the 1989 Eagle Fire in northernCalifornia (NWCG 1993).

Figure 5. The pocket card stresses that under nocircumstances should a frontal assault on an advancinggrass fire be undertaken. Photo from Clayton et al. (1987).

What is the Basis of the Grassland FireBehaviour Pocket Card?

The Alexander and Fogarty (1997) pocket carddistills a large amount of research knowledgeon wildland fire behaviour in general andspecifically as it pertains to grasslands (Wilson1988; Cheney and Sullivan 19972) that is bothdirectly and indirectly relevant to the issue offirefighter safety (Figure 6). For example, theinformation presented on the front side of thepocket card (Figure 1a) enables one to judgewhether or not a firebreak, a road or a preparedfireguard downwind of a spreading grass firewill stop the advancing flame front (Figure 7).Firefighters can accordingly develop or adjusttheir control strategy without jeopardizing theirown well-being as a result of feeling compelledto take the fire “head on” in order to protect avalue-at-risk (e.g., a farm house) or to stop thefire at all costs.

In contrast to the fire danger index climatologyderived pocket card of Andrews et al. (1998),the estimates of the various fire behaviourcharacteristics incorporated into the grasslandfire behaviour pocket card are based on thequantitative predictions obtained from theCanadian Forest Fire Behaviour Prediction(FBP) System (Forestry Canada Fire Danger.

Figure 6. The pocket cardhas incorporated both thebasic fire behaviour datagathered from theexperimental fires carried outin the Northern Territory ofAustralia by the CSIRObushfire research group andthe firebreak effectivenessmodel developed from thisstudy. Photos from Davidson(1988) and CSIRO Divisionof Forestry and ForestProducts Annual Report.

2Cheney and Sullivan’s (1997) book constitutes a tour de force in the field of wildland fire behaviour and is

recommended reading for anyone involved in grassland fire suppression.

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Figure 7. The pocket card provides guidance on theminimum firebreak width necessary to halt a grass fire’sforward progress. Photo courtesy of D.R. Page, Woodsand Forests Department of South Australia.

Group 1992). The predictions for fire spreadand flame front intensity were obtained fromthe rate of spread model for the standing grassfuel type (O-1b) in the FBP System (Figure 8)assuming a constant fuel load (3.5 t/ha), degreeof curing (100%), moisture content (Fine FuelMoisture Code 93.2, equating to <6% in fullycured grass), and a zero slope as stated on theback of the pocket card (Figure 1b). The firearea and perimeter estimates are based on theFBP System’s simple elliptical fire growthmodel (Figure 9). For more information on thetechnical basis of the grassland fire behaviourpocket card one should consult Fogarty andAlexander (1999).

Figure 8. The fire spread and intensity estimates in thepocket card are based on Canadian Forest Fire BehaviourPrediction System Fuel Type O-1b (Standing Grass).Photo from De Groot (1993).

Figure 9. The fire growth projections in the pocket cardassume an elliptical fire shape. Photo courtesy of D.D.Wade, USDA Forest Service.

How Does the Grassland Fire BehaviourPocket Card Work?

The pocket card requires only one input,namely an on-site estimate of wind speed(Figure 10) based on the Beaufort Wind Scale(List 1951, p. 119), which is reproduced on theback side of the card (Figure 1b); a measured orforecasted value could be used as well. Giventhe associated fire behaviour predictions, a mapand general knowledge of the area (e.g., roadwidths), and knowing what the prevailing winddirection is, fire suppression personnel are ableto make assessments as to how far a grass fireis likely to advance. In turn, they are able todetermine very early on whether warningsshould be issued to residents and landownersdownwind of the fire so that they can evacuatesafely and/or make preparations to protect theirassets. Simply put, the pocket card gives theinitial attack fire boss or incident commander ameans of making an initial estimate of potentialworst case fire behaviour which can be factoredinto the fire suppression strategy (e.g., the sizeor magnitude of the fire problem in terms of theresources that will be required to contain thefire). A detailed example of how to use thegrassland fire behaviour pocket card, suitablefor training purposes, is given in Fogarty andAlexander (1999).

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Figure 10. An estimate of the probable fire behaviourcharacteristics in grasslands can be obtained from thepocket card based solely on an on-site estimate of theprevailing wind speed. Photo courtesy of J. McMeeking,New Zealand Department of Conservation.

Where Can I Get a Copy of the GrasslandFire Behaviour Pocket Card?

Copies of the Alexander and Fogarty (1997)grassland fire behaviour pocket card, as well asthe associated Fire Technology Transfer Note20 (Fogarty and Alexander 1999) and thepublication by Rasmussen and Fogarty (1997),are available upon request from: Forest & RuralFire Research Programme, Forest Research,P.O. Box 29237, Christchurch, New Zealand(email: grant.pearce@forestresearch.co.nz).

Furthermore, a poster (Alexander and Fogarty2001) on the grassland fire behaviour pocketcard that utilizes all the illustrations containedin this Fire Technology Transfer Note is alsoavailable upon request (see back cover).

Acknowledgements

The review comments on the original versionof this paper by G.J. Baxter, then of ForestResearch are gratefully acknowledged. Theassistance of H.G. Pearce of Forest Researchin the preparation of this Fire TechnologyTransfer Note is duly acknowledged.

About the Authors

Dr. Marty Alexander is a Senior Fire BehaviourResearch Officer with the Canadian ForestService (CFS) based at the Northern ForestryCentre in Edmonton, Alberta. Marty held aVisiting Fire Research Scientist position atNew Zealand’s Forest Research in Rotorua

during a one-year secondment from the CFS in1992-93; he was in turn made a HonoraryMember of the Forest and Rural FireAssociation of New Zealand FRFANZ for “hiscontributions to vegetation fire management inNew Zealand”. He has continued to serve as anadvisor and collaborator to the ForestResearch forest and rural fire researchprogramme since his return to Canada in April1993.

Liam Fogarty was employed as a Forest andRural Fire Research Scientist at ForestResearch in Rotorua from July 1993 to March1998; he was also made an Honorary Memberof FRFANZ for the many contributions he hadmade to New Zealand vegetation firemanagement. At the time the manuscript onwhich this Fire Technology Transfer Note wasprepared, Liam was employed as a FireManagement Consultant to the Berau ForestManagement Project, Kalimantan Timur,Indonesia. He is currently a Senior Foresterwith Greenfield Resource Options Pty. Ltd.,Brisbane, Queensland.

References Cited

Alexander, M.E. 1998. A wildland fire behaviourresearcher’s perspective of firefighter safety inCanada. In Proceedings Canada/US Wildland FireSafety Summit. International Association ofWildland Fire, Fairfield, Washington. pp 37.

Alexander, M.E.; Fogarty, L.G. 1997. A simplefield guide for estimating the behaviour andsuppression requirements of fires driven by windcoming from a constant direction in open, fullycured grasslands at low fuel moisture. NewZealand Forest Research Institute, Rotorua, NewZealand, and National Rural Fire Authority,Wellington, New Zealand. Pocket card.

Alexander, M.E.; Fogarty, L.G. 2001. A pocketcard for predicting fire behaviour in grasslandsunder severe burning conditions. In Pearce, G.;Lester, L (technical coordinators.). Bushfire 2001Proceedings, Australasian Bushfire Conference(July 3-6, 2001, Christchurch, New Zealand). NewZealand Forest Research Ltd., Rotorua, NewZealand. pp 315-316.

Andrews, P.L.; Bradshaw, L.S.; Bunnell, D.L.;Curcio, G.M. 1998. Fire danger rating pocket cardfor firefighter safety. In Preprints Second

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Anon. 1997. Video available showing the recoveryof a severely burned volunteer firefighter. Wildfire6(1): 64.

Cheney, P.; Sullivan, A. 1997. Grassfires: fuel,weather and fire behaviour. CSIRO Publishing,Collingwood, Victoria, Australia. 102 p.

Butler, B.W.; Shannon, K. (editors). 2000.Proceedings of the 2000 International WildfireSafety Summit. International Association ofWildland Fire, Montana City, Montana. 205 p.

Clayton, B.; Day, D.; McFadden, J. 1987.Wildland firefighting. State of California, Officeof Procurement, North Highlands, California.136 p.

Davidson, S. 1988. Predicting the effectiveness offirebreaks. Rural Research 139 (Winter): 11-16.

De Groot, W.J. 1993. Examples of fuel types inthe Canadian Forest Fire Behaviour Prediction(FBP) System. Forestry Canada, Northern ForestryCentre, Edmonton, Alberta. Poster with text.

ETC and CIFFC 2000. Wildland fire -- safety onthe fireline. Environmental Training Centre(ETC), Hinton, Alberta, and Canadian InteragencyFire Centre (CIFFC), National Training WorkingGroup, Winnipeg, Manitoba. CD-ROM.

Fogarty, L.G. 1996. Two rural/urban interface firesin the Wellington suburb of Karori: assessment ofassociated burning conditions and fire controlstrategies. New Zealand Forest Research Institute,Rotorua, New Zealand, and National Rural FireAuthority, Wellington, New Zealand. FRI Bulletin197, Forest and Rural Fire Scientific andTechnical Series, Report No. 1. 16 p.

Fogarty, L.G.; Alexander, M.E. 1999. A fieldguide for predicting grassland fire potential:derivation and use. Forest Research, Rotorua,New Zealand, Natural Resources Canada,Canadian Forest Service, Ottawa, Ontario, andNational Rural Fire Authority, Wellington, NewZealand. Fire Technology Transfer Note No. 20.10 p.

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Directorate, Ottawa, Ontario. Information ReportST-X-3. 63 p.

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List, R.J. 1951. Smithsonian meteorological tables.6th revised edition. Smithsonian Institute Press,Washington, D.C. 527 p.

NFPA. 1992. Firestorm ‘91 case study. NationalFire Protection Association (NFPA), Quincy,Massachusetts. 31 p.

NWCG. 1990. Single resource boss – crew,S-230 slide set. National Wildfire CoordinatingGroup (NWCG), Boise, Idaho. National FireEquipment System Publication NFES 2159.

NWCG. 1993. Look up, look down, look around.National Wildfire Coordinating Group (NWCG),Boise, Idaho. National Fire Equipment SystemPublication NFES 2244. VHS videotape.

NWCG. 1996. Common denominators of firebehaviour on tragedy and near-miss wildland fires.National Wildfire Coordinating Group (NWCG),Boise, Idaho. National Fire Equipment SystemPublication NFES 2225. 23 p.

NWCG Safety and Health Working Team. 1997.Historical wildland firefighter fatalities 1910-1996. 2nd edition. National Wildfire CoordinatingGroup (NWCG), Boise, Idaho. National FireEquipment System Publication NFES 1849. 38 p.

Rasmussen, J.H.; Fogarty, L.G. 1997. A case studyof grassland fire behaviour and suppression: theTikokino Fire of 31 January 1991. New ZealandForest Research Institute, Rotorua, New Zealand,and National Rural Fire Authority, Wellington,New Zealand. FRI Bulletin No. 197, Forest andRural Fire Scientific and Technical Series, ReportNo. 2. 18 p. + appendix.

Wilson, A.A.G. 1988. Width of firebreak that isnecessary to stop grass fires: some fieldexperiments. Canadian Journal of Forest Research18: 682-687.

Wilson, C.C.; Sorenson, J.C. 1978. Some commondenominators of fire behaviour on tragedy andnear-miss forest fires. U.S. Department ofAgriculture, Forest Service, Northeast State andPrivate Forestry, Broomall, Pennsylvania.Publication NA-GR-8. 31 p.

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