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Track: Natural Resources and Conservation
Joseph Meyer
Yosemite National Park
Yosemite, CA 95389
Telephone: 209-379-1887
Fax: 209-379-1886
E-mail: meyer@yose.nps.gov
FARSITE GIS Modeling in the 1996 Yosemite Ackerson Fire
During the Ackerson Complex fires of 1996, the largest fire in park history, Yosemite NP used GIS effectively to fight the fire while at the same time protecting resources. A majority of the fire was within Yosemite NP, but about 15% of the fire was on Stanislaus NF lands. To the best of our knowledge, this was the first time FARSITE was applied to a wildfire - it is generally used for planning "management ignited prescribed fires" and for managing "prescribed natural fires" (i.e. lightning caused, burning within certain parameters, aka a prescription). FARSITE requires 5 spatial data layers (elevation, slope, aspect, fuels and canopy cover) and 1 non-spatial dataset (weather). The elevation, slope and aspect was derived from a Digital Elevation Model. Yosemite's fuels data was derived from an NDVI classification of vegetation - fuels is generally the most difficult layer to generate, and is often simply a reclass of vegetation. Canopy cover was derived from a reclass of vegetation. Early in the
Ackerson fires, FARSITE had to be calibrated to adjust for the very heavy fuels and hot, dry weather conditions. At this point the fire was largely unmanageable and FARSITE was used to better understand the fire's behavior and spread. After calibrated, FARSITE was used to predict fire spread under different weather scenarios. We learned various things about FARSITE during the Ackerson fires. First, the fuel models have to be calibrated to reflect different conditions. Second, although an automatic weather stations was within a few miles of the fire, FARSITE did not start performing well until we have weather data from the fireline (or very near vicinity). Third, although we made great strides in timeliness, the GIS needs to be in fire camp to be of greatest use. Fourth, it is important to have a fuels data layer that accurately reflects not only the fuels types but the heterogeneity of the fuels - this is where a reclass of a vegetation map to derive fuels generally falls down. FARSITE is a useful
tool, but many factors affecting fire progression are poorly understood (e.g. weather) or difficult to predict or model. In addition to FARSITE, there are other ways that GIS was used during the Ackerson complex: fire history maps, maps showing location of resources, public information maps, etc.
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