Crystal S. Stonesifer

Large airtanker use and outcomes in suppressing wildland fires in the United States

Wildfire activity in the United States incurs substantial costs and losses, and presents challenges to federal, state, tribal and local agencies that have responsibility for wildfire management. Beyond the potential socioeconomic and ecological losses, and the monetary costs to taxpayers due to suppression, wildfire management is a dangerous occupation. Aviation resources, in particular large airtankers, currently play a critical role in wildfire management, and account for a relatively large share of both suppression expenditure and firefighting fatalities. A recent airtanker modernisation strategy released by the US Department of Agriculture Forest Service and the US Department of Interior highlighted cost effectiveness as the fundamental tenet of both the replacement strategy and the use of aerial firefighting resources. However, determining the cost effectiveness of alternative airtanker fleets is challenging due to limited data and substantial uncertainty regarding aerial firefighting effectiveness. In this paper, we significantly expand on current airtanker usage and effectiveness knowledge, by incorporating spatially explicit drop location data linked to firefighting resource orders to better identify the period in the fire history when drops occurred, and through characterisation of the resulting outcomes of fires that received drops during initial attack. Our results confirm earlier work suggesting extensive use of large airtankers on extended attack, despite policy suggesting priority use in initial attack. Further, results suggest that containment rates for fires receiving large airtanker use during initial attack are quite low. We explore possible causes for these results, address potential limitations with our methods and data, and offer recommendations for improvements in data collection and aviation management.

Fighting fire in the heat of the day: an analysis of operational and environmental conditions of use for large airtankers in United States fire suppression

Large airtanker use is widespread in wildfire suppression in the United States. The current approach to nationally dispatching the fleet of federal contract airtankers relies on filling requests for airtankers to achieve suppression objectives identified by fire managers at the incident level. In general, demand is met if resources are available, and the dispatch model assumes that this use is both necessary and effective. However, proof of effectiveness under specific conditions of use in complex environments has not been empirically established. We geospatially intersected historical drop data from the federal contract large airtanker fleet with operational and environmental factors to provide a post hoc assessment of conditions of use for the 2010–12 fire seasons in the conterminous United States. Our findings confirm previous results demonstrating extensive use in extended attack. Additionally, we show that use is generally within guidelines for operational application (aircraft speed and height above ground level) and often outside of environmental guidelines suggestive of conditions conducive for most effective use, including drop timing with respect to response phase (initial attack v. extended attack), terrain, fuels and time of day. Finally, our results suggest that proximity to human populations plays a role in whether airtankers are dispatched, suggesting that prioritisation of community protection is an important consideration. This work advances efforts to understand the economic effectiveness of aviation use in federal fire suppression.

Near-term probabilistic forecast of significant wildfire events for the Western United States

Fire danger and potential for large fires in the United States (US) is currently indicated via several forecasted qualitative indices. However, landscape-level quantitative forecasts of the probability of a large fire are currently lacking. In this study, we present a framework for forecasting large fire occurrence – an extreme value event – and evaluating measures of uncertainties that do not rely on distributional assumptions. The statistical model presented here incorporates qualitative fire danger indices along with other location and seasonal specific explanatory variables to produce maps of forecasted probability of an ignition becoming a large fire, as well as numbers of large fires with measures of uncertainties. As an example, 6 years of fire occurrence data from the Western US were used to study the utility of two fire danger indices: the 7-Day Significant Fire Potential Outlook issued by Predictive Services in the US and the National Fire Danger Rating’s Energy Release Component. This exercise highlights the potential utility of the quantitative risk index as a real-time decision support tool that can enhance managers’ abilities to discriminate among planning areas in terms of the likelihood and range of expected significant fire events. The approach is applicable wherever there are archived historical data from both observed fires and fire danger indices.

A simulation and optimisation procedure to model daily suppression resource transfers during a fire season in Colorado

Sharing fire engines and crews between fire suppression dispatch zones may help improve the utilisation of fire suppression resources. Using the Resource Ordering and Status System, the Predictive Services’ Fire Potential Outlooks and the Rocky Mountain Region Preparedness Levels from 2010 to 2013, we tested a simulation and optimisation procedure to transfer crews and engines between dispatch zones in Colorado (central United States) and into Colorado from out-of-state. We used this model to examine how resource transfers may be influenced by assignment shift length, resource demand prediction accuracy, resource drawdown restrictions and the compounding effects of resource shortages. Test results show that, in certain years, shortening the crew shift length from 14 days to 4 days doubles the yearly transport cost. Results also show that improving the accuracy in predicting daily resource demands decreases the engine and crew transport costs by up to 40%. Other test results show that relaxing resource drawdown restrictions could decrease resource transport costs and the reliance on out-of-state resources. The model-suggested assignments result in lower transport costs than did historical assignments.

Predicting wildfire ignitions, escapes, and large fire activity using Predictive Service’s 7-Day Fire Potential Outlook in the western USA

Can fire potential forecasts assist with pre-positioning of fire suppression resources, which could result in a cost savings to the United States government? Here, we present a preliminary assessment of the 7-Day Fire Potential Outlook forecasts made by the Predictive Services program. We utilized historical fire occurrence data and archived forecasts to assess how well the 7-Day Outlook predicts wildfire ignitions and escaped fires, ultimately to help characterize the effectiveness of this tool for prepositioning national firefighting resources. The historical fire occurrence data track ignitions on all land ownerships; from this dataset, we established number and location of ignitions and final fire size for the years 2009-2011 for Predictive Service Areas (PSAs) within the Northwest and Southwest Geographic Areas. These data were then matched to the corresponding PSA and appropriate forecast for each of the seven days prior to the ignition date. Final fire size was used as a metric to establish whether an ignition escaped initial attack, with fires greater than 121.4 hectares (300 acres) considered escaped. Our results show that 7-Day Outlook values yield better-than-random prediction of large fire activity, although there is wide variation in this relationship among individual PSAs. In addition, the number of escaped fires increased with the number of ignitions, with this relationship showing a distinct regional pattern. Fires were more likely to escape during certain times of the year, with this season being earlier in the Southwest than in the Northwest. Significantly higher numbers of escaped fires per ignition occurred during days considered to be high risk by the meteorologist than on lower-risk days.