NIST Technical Note 1796 A Case Study of a Community Affected by the Witch and Guejito Fires: Report #2 – Evaluating the Effects of Hazard Mitigation Actions on Structure Ignitions Alexander Maranghides Derek McNamara William Mell Jason Trook Blaza Toman NIST Technical Note 1796 A Case Study of a Community Affected by the Witch and Guejito Fires Report: #2 – Evaluating the Effects of Hazard Mitigation Actions on Structure Ignitions Alexander Maranghides Fire Research Division Engineering Laboratory Derek McNamara McNamara Consulting Golden, CO William Mell U.S. Forest Service Seattle, WA Jason Trook 850 Couer d’Alene Tribe Coeur d’Alene, ID Blaza Toman Statistical Engineering Division Engineering Laboratory May 2013 U.S. Department of Commerce Rebecca Blank, Acting Secretary National Institute of Standards and Technology Patrick D. Gallagher, Under Secretary of Commerce for Standards and Technology and Director Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose. National Institute of Standards and Technology Technical Note 1796 Natl. Inst. Stand. Technol. Technical Note 1796, 107 pages (May 2013) This publication was a joint effort between the National Institute of Standards and Technology and the United States Forest Service (USFS). Cover Page Photo: The Trails Monday 22 October 2007, Photo Courtesy of Michael Bunnell, Used by Permission ii Table of Contents Abstract ....................................................................................................................................... 1 1.0 Background ........................................................................................................................... 2 2.0 Introduction ........................................................................................................................... 3 3.0 Summary of Objectives and Findings in First Trails Report ................................................ 5 3.1 Defensive Actions, Fire Timeline and Fire Direction ....................................................... 5 4.0 Objectives of this Report ...................................................................................................... 7 5.0 Materials and Methods .......................................................................................................... 8 5.1 Firewise Checklist Data Collection and Processing ......................................................... 8 5.2 Additional Data Processing............................................................................................. 12 5.3 Data Analysis Procedures ............................................................................................... 15 6.0 Data Collection, Production and Analysis Limitations....................................................... 20 6.1 Field Data Collection ...................................................................................................... 21 6.2 Data Production .............................................................................................................. 22 6.3 Exposure Determinations ................................................................................................ 23 6.4 Data Analysis Limitations ............................................................................................... 24 7.0 Results ................................................................................................................................. 25 7.1 Applicability of Firewise at the Trails (Zone Concept) .................................................. 25 7.2 Presence of Firewise Treatments at the Trails ................................................................ 27 7.3 Firewise Effectiveness (Individual Treatments) ............................................................. 28 7.4 High Hazard Area Determination ................................................................................... 31 7.5 Exposure Method Evaluations ........................................................................................ 31 7.6 Firewise Effectiveness (Two Exposure Methods) .......................................................... 33 7.7 Defensive Actions as a Function of High/Low Hazard Exposure .................................. 38 8.0 Discussion ........................................................................................................................... 40 8.1 Analyzing if Firewise treatments are applicable within the Trails ................................. 40 8. 2 Determining if Firewise treatments were present at the Trails, prior to the Witch and Guejito Fires.......................................................................................................................... 42 8.3 Evaluating the effectiveness of Firewise treatments in reducing structure ignitions at the Trails. .................................................................................................................................... 43 8.4 Mapping fire exposure profiles within the Trails. .......................................................... 43 8.5 Evaluating the effectiveness of Firewise treatments in reducing structure ignitions in context of potential exposure. ............................................................................................... 44 8.6 Evaluating of defensive action in terms of Firewise treatments and as a function of exposure. ............................................................................................................................... 44 8.7 Future WUI post-fire case studies................................................................................... 44 9.0 Summary ............................................................................................................................. 45 10.0 Conclusions/Recommendations ........................................................................................ 46 11.0 Future Work ...................................................................................................................... 47 12.0 Acknowledgements ........................................................................................................... 48 Appendix A ............................................................................................................................... 75 Appendix B ............................................................................................................................... 79 Appendix C ............................................................................................................................... 82 Appendix D ............................................................................................................................... 85 Appendix E ............................................................................................................................... 88 iii Appendix F................................................................................................................................ 90 Appendix G ............................................................................................................................... 93 13.0 References ......................................................................................................................... 98 iv List of Figures Figure 1 Overview of the entire extent of the Witch and Guejito Fires in context with the United States. Also portrayed is the study area within the fire perimeter and the origins of the fires. .............................................................................................................................. 49 Figure 2 Fire approach to the Trails Community from the Witch and Guejito Fires. Back ground imagery is 1 foot horizontal resolution color imagery flown shortly after the fires. ... 50 Figure 3 Trails community in relation to Witch fire perimeter with primary structures displayed by damaged status. Back ground imagery is 3 inch horizontal resolution color imagery from 2005. ...................................................................................................... 51 Figure 4 Hillshade portraying topography in and around the Trails. Hillshade created from Light Intensity Detection and Ranging (LIDAR) derived 1.5 meter digital elevation model obtained from the United States Geologic Survey (USGS). .............................. 52 Figure 5 Property lot types in the Trails Community. Back ground imagery is 3 inch horizontal resolution color imagery from 2005. ........................................................................... 53 Figure 6 Primary structure densities per square mile for the Witch and Guejito Fires. Derived using the ArcGIS™ Point Density Tool with a circle window having a radius of approximately 200 meters (660 feet) and an output cell size of 3 meters (10 feet). .... 54 Figure 7 Residential structure density in and around the Trails. Derived using the ArcGIS™ Point Density Tool with a circle window having a radius of approximately 200 meters (660 feet) and an output cell size of 3 meters (10 feet). ............................................... 55 Figure 8 Defensive actions on residential