IGNITION THRESHOLDS FOR GRASSLAND FUELS AND IMPLICATIONS FOR ACTIVITY CONTROLS ON PUBLIC CONSERVATION LAND IN CANTERBURY A thesis submitted in fulfilment of the requirements for the Degree of Master of Forestry Science in the University of Canterbury by Heather M. Wakelin University of Canterbury 2010 ii Table of Contents i. Acknowledgements ........................................................................................................ vii ii. Abstract ........................................................................................................................... ix iii. List of Figures ................................................................................................................. xi iv. List of Tables .................................................................................................................. xv v. List of Abbreviations .................................................................................................... xix Chapter 1. Background ........................................................................................................... 1 1.1 Introduction ............................................................................................................... 1 1.2 Grasslands, Wetlands, and Fire Influences ................................................................ 1 1.2.1 Grassland and Wetland Classification in Canterbury and the South Island High Country… .......................................................................................................................... 2 1.2.2 Fire History and South Island Grasslands ......................................................... 7 1.2.3 Wildfire Events in New Zealand ..................................................................... 10 1.3 Department of Conservation (DOC) ........................................................................ 13 1.3.1 Canterbury Region ........................................................................................... 13 1.3.2 Land Tenure Review ....................................................................................... 16 1.3.3 Ō Tū Wharekai Wetland Restoration Project .................................................. 20 1.4 Rural Fire Management in New Zealand ................................................................ 26 1.5 The New Zealand Fire Danger Rating System (NZFDRS) ..................................... 27 1.5.1 The Fire Weather Index (FWI) System ........................................................... 28 1.5.2 The Fire Behaviour Prediction (FBP) System ................................................. 31 1.5.3 Fire Danger Class Scheme ............................................................................... 32 1.5.4 Summary of the NZFDRS ............................................................................... 34 1.6 Study Overview ....................................................................................................... 36 1.6.1 Study Structure and Significance .................................................................... 36 1.6.2 Research Objective and Questions .................................................................. 36 1.6.3 Thesis Structure ............................................................................................... 37 Chapter 2. Fire Ignitions in Grassland Fuels: A Literature Review ................................ 39 2.1 Introduction ............................................................................................................. 39 2.2 Key Terms and Concepts ......................................................................................... 39 2.2.1 The Fire Process .............................................................................................. 39 2.2.2 Ignition Thresholds and Associated Concepts ................................................. 41 2.3 Main Ignition Sources of Concern in this Study ..................................................... 44 2.3.1 Hot Metal (hot vehicle or machinery parts) ..................................................... 45 2.3.2 Hot Carbon Emissions (carbon emissions and gas from vehicle exhausts) ..... 50 2.3.3 Metal Sparks .................................................................................................... 52 iii 2.3.4 Organic Embers ............................................................................................... 52 2.3.5 Open Flame ..................................................................................................... 55 2.4 Other Significant Ignition Sources .......................................................................... 57 2.4.1 Spotting............................................................................................................ 57 2.4.2 Hot Air/Gas Ignition Sources .......................................................................... 60 2.4.3 Glass ................................................................................................................ 61 2.4.4 Power Lines ..................................................................................................... 62 2.4.5 Self-heating ...................................................................................................... 62 2.4.6 Miscellaneous Ignition Sources ....................................................................... 63 2.5 Brief Overview of Grass Fires in Canterbury .......................................................... 63 2.6 Summary.................................................................................................................. 68 Chapter 3. Methods ............................................................................................................... 73 3.1 Introduction ............................................................................................................. 73 3.2 Grass Samples and Moisture Content ...................................................................... 73 3.2.1 Sample Collection and Preparation ................................................................. 73 3.2.2 Moisture Content Classes ................................................................................ 76 3.3 Laboratory Experiments .......................................................................................... 78 3.4 Ignition Sources ....................................................................................................... 81 3.4.1 Hot Metal Contact ........................................................................................... 81 3.4.2 Hot Carbon Emissions ..................................................................................... 88 3.4.3 Metal Sparks .................................................................................................... 92 3.4.4 Organic Embers ............................................................................................... 94 3.4.5 Open Flame ..................................................................................................... 96 3.4.6 Summary of Laboratory Experiments ............................................................. 99 3.5 Field Experiments .................................................................................................... 99 3.5.1 Hot Metal Contact ......................................................................................... 101 3.5.2 Hot Carbon Emissions ................................................................................... 102 3.5.3 Metal Sparks .................................................................................................. 103 3.5.4 Organic Embers ............................................................................................. 104 3.5.5 Open Flame ................................................................................................... 104 3.5.6 Summary of Field Experiments ..................................................................... 104 Chapter 4. Results ............................................................................................................... 105 4.1 Introduction ........................................................................................................... 105 4.2 Laboratory Experiments ........................................................................................ 105 4.2.1 Data Analysis ................................................................................................. 105 4.2.2 Hot Metal ....................................................................................................... 108 4.2.3 Hot Carbon Emissions ................................................................................... 112 iv 4.2.4 Metal Sparks .................................................................................................. 115 4.2.5 Organic Embers ............................................................................................. 116 4.2.6 Open Flame ................................................................................................... 117 4.3 Field Experiments .................................................................................................. 120 4.3.1 Hot Metal Contact ......................................................................................... 120 4.3.2 Hot Carbon Emissions ................................................................................... 122 4.3.3 Metal Sparks .................................................................................................