An unfortunate reality is that destructive fires are occurring in communities across the country, such as the Waldo and Black Forest in Colorado, and most recently the Chimney Tops 2 fire in Great Smoky Mountains National Park in the fall of 2016. The Chimney Tops 2 fire was hit by sustained strong winds, merged with other fires, and burned out of the park into the tourist town of Gatlinburg, Tennessee. Ultimately 14 people lost their lives, and more than 2,460 structures were damaged or destroyed. A common thread from people in that area was this was a fire “like they had never seen before.” This was a fire that seemed out of the realm of possibility to locals.
A fire similar to the Chimney Tops 2, is an all too real scenario for Rocky Mountain National Park (RMNP) and the Town of Estes Park, as well as our neighbor towns of Allenspark and Glen Haven and everything in between. RMNP and its neighbors have some of the most at risk Wildland Urban Interface (WUI) in the National Park System.
On any given summer season day, the Estes Valley and Rocky Mountain National Park attracts a substantial number of visitors. On some of the busiest days of 2016, RMNP had over 12,000 vehicles enter the park which translates to over 30,000 people. On busy weekends such as the Scottish Festival in Estes Park, over 60,000 visitors may be in town. This high number of visitors and their vehicles often gridlock town and park roads. This limits emergency vehicle passage as well as severely handicaps the ability to evacuate during an emergency.
Extreme fires in our area are low frequency, but have the potential to be very high severity. While infrequent, the environmental conditions which would support extreme fire growth (several days low RH, low fuel moisture and high winds) happen several times each year. It is just a matter of time before these conditions meet up with an ignition.
Aiming to learn from the Chimney Tops 2 fire, a workshop was organized of emergency responders from in and around the Estes Park area. The overarching objective was to understand how local, county, state, and federal agencies would work together during a catastrophic wildfire scenario. The greater Estes Park area has a history of interagency partners working together exceptionally well as demonstrated during the 2012 Fern Lake Fire and the 2013 Flood. The intent of this workshop was to get our partners together and walk through each agencies roles and responsibilities, should a wildfire burn through the Town of Estes Park.
A wildfire scenario was developed that represented a realistic and possible “worst case” scenario: a wildfire that spread rapidly into heavily populated areas of Estes Park, impacting private property as well as critical infrastructure. For this scenario, actual historical weather data were queried for periods of high fire danger in the late summer/early fall when fuels are dry, temperatures are still warm, and there is potential for strong winds. Based on an analysis of 10 years of data from the Estes Park remote automated weather station (RAWS), (located just west of the Beaver Meadows Visitor Center), the weather conditions presented on September 18, 2010 was chosen for the scenario.
On September 18, 2010 the Energy Release Component (ERC) for the Estes Park RAWS was 80. This value of ERC is considered “Extreme” (above 97th percentile) and conducive to rapid fire spread and extreme fire behavior. Temperatures in southwest Larimer County were 2-4 degrees F warmer than average and precipitation was less than 50% of normal for the month. Dead fuel moistures were at or near record low values (10-hour time lag fuel moisture: 2%, 100-hour: 7%, 1000-hour: 8%). Herbaceous fuels were largely cured (60% fuel moisture) and live woody fuel moisture was below average.
Historical analysis indicates that during the month of September, winds at the Estes Park RAWS occur most frequently from the west-southwest. On September 18, 2010 winds during the burn period reached a maximum of 28 miles per hour. For this simulation, west-southwest winds were increased to 50 miles per hour during the last 3 hours of the initial burn period (1700-2000, September 18). This was done to simulate a major downslope wind event. These types of events are not uncommon in the fall and winter months along the eastern slopes of the Front Range of Colorado. Other than the increased winds on September 18, all other weather inputs utilized in this scenario were the actual conditions experienced on that day. See Table 1 below for hourly weather recorded on September 18, 2010.
The Near Term Fire Behavior (NTFB) model within the Wildland Fire Decision Support System (WFDSS) was used to model potential fire behavior in this scenario. NTFB is a two-dimensional fire growth model that uses spatial information on topography, fuels, weather, and wind to model fire growth. NTFB incorporates existing models for surface fire, crown fire, spotting, post-frontal combustion, and fire acceleration. NTFB outputs are displayed as a modeled fire progression, which allows visual observation of how the modeled fire reacts to heterogeneous fuel and weather conditions for the duration of the simulation. The model utilizes a variable weather and fuel moisture stream (changes hourly) and as mentioned previously, this scenario utilized actual weather and fuels inputs with the exception of increased winds on the evening of September 18, 2010.
The ignition for this simulation was a 20 acre fire located on the southwest aspect of Eagle Cliff, near the park boundary. This location is characterized by open ponderosa pine overstory with a predominantly grass understory conducive to rapid fire spread under dry, windy conditions. Access to Eagle Cliff, like other areas in the park, could be limited and present a challenge to initial attack. Unchecked growth to 20 acres with limited initial attack and no air support was considered a realistic starting point, representative of high or extreme fire danger and fall wind events.
At the end of the initial burn period (12 hours on September 18), the fire had grown to 2,069 acres. At the end of the second burn period, acreage burned had increased to 6,630. This scenario assumes that no suppression action was taken on any portion of the fire. With the modeled wind, air support would not be possible for fire suppression. Given the rate of fire spread, it is likely that all suppression crews would be assigned to other tasks and unable to complete suppression activities.
Agency resources that are available to respond to wildfire incidents depend on time of year and local preparedness levels. Most fire agencies have larger staff in the late spring to early fall time period which has traditionally been “fire season,” however large destructive fires have happened year-round. During very high to extreme fire danger time periods, agencies may also bolster local initial response resources as available. The actual number of resources that can respond at any given time has many factors; time of year, other fires in the area, or possible local resources needing to respond to fires in other parts of the country. As all local fire districts and departments rely on volunteer staffing, even family vacations can impact the ability of an agency to respond and members available.
Aviation resources are a valuable tool during the initial response to wildfires. During the summer season, the Forest Service manages the exclusive use Northern Colorado helicopter and crew, and the State and BLM may have Single Engine Air Tankers (SEAT) within our response zone. In addition, there may be Type 1 and Type 2 helicopters staged in the local area as well as heavy air tankers. These resources are managed at the National level and may be moved around the country where the fire danger and/or need may be greater.
An important aspect in utilizing aviation resources is that often when there are extreme fire conditions, there are also extreme flying conditions. Winds can be too high for aviation assets to operate (helicopters and Single Engine Air Tankers (SEAT) are unable to fly in wind speeds above sustained 30 knots (35 mph) and/or gust spread of 15 knots (17 mph). In addition, the extreme mountainous terrain and heavy concentration of people can limit the effective use of heavy air tankers.
For more information on this training workshop: Mike Lewelling (970)-586-1287