Issue link: https://read.dmtmag.com/i/43993
Assessing Wildfire Response: Jumping Right into It BEYONDMAPPING L BY JOSEPH BERRY ast month's "Beyond Mapping" column (see "Assessing Wildfire Response: Oneth by Land, Twoeth by Air," GeoWorld, August 2011, page 10) noted that wildland fire initial attack gener- ally takes three forms: 1) helicopter land- ing, 2) helicopter rappelling or 3) ground attack, as determined by terrain and land- cover conditions (also "smoke-jumping," but that's a whole other story). The previous discussion described a spatial model developed by Fire Program Solutions (see "Author's Notes," page 11) for identifying helicopter landing zones. The following discussion extends the analysis to modeling and comparing the response times for the three different initial attack modes for all locations within a project area. Down the Rope Figure 1 identifies the major steps in determining "Rappel Country." There are some among us so heroic (crazy?) that they rappel out of a helicopter just to get to a wildfire before the crowd. Rappel country is defined as the areas where rappelling is the most effective initial attack mode based on project assumptions. In addition to general exclusions (e.g., open water, 10,000-foot altitude ceiling), rappel- ling must consider four other highly variable physical exclusions: 1) extremely steep terrain (greater than 80 degrees), 2) very dense forest canopies, 3) very tall forest canopies and 3) dense, tall brush. The simple binary model in the Joseph Berry is a principal in Berry & Associates, consultants in GIS technology. He can be reached via e-mail at jkberry@du.edu. 10 upper portion of Figure 1 is used to identify locations suitable for rappel- ling (1 = OK; 0 = No Go), where the fearless can jump from a hovering helicopter and slide down a rope (up to a couple hundred feet) between trees to the ground. The figure's lower portion uses a simple distance calculation to identify the travel time within a 75-mile work- ing circle about a helibase, assuming a defined airspeed, round-trip fuel GEO W ORLD / SEPTEMBE R 2O11 Figure 1. A diagram describes the major steps and considerations in modeling wildfire helicopter rappel-attack travel time. capacity and other defining factors. By combining the binary map of rappel country and the helicopter travel-time surface, an estimated travel time from the closest helibase to every Helicopter Rappelling Accessible location in a project area is determined. In a similar "binary multiplication" manner, the helicopter travel-time to each Effective Landing Zone can be calculated. However, the landing crew must hike to a wildland fire outside the landing zone. This secondary travel is modeled in a manner similar to that used for the off-road movement of the ground-response model. The helicopter flight time to a landing zone and the ground-hiking time to the fire are combined for an overall travel time from the clos- est helibase to every Helicopter Landing Accessible location in a project area. Across the Land Figure 2 outlines the major steps in modeling the combined on- and off-road response time for a ground-attack crew. On-road travel is determined by the typical speed for different road types. The calculations for deriving the travel time to cross a 30-meter grid cell are shown in the rows of the table for five classes of roads from major highways (R1) to backwoods roads (R5). Note that the slowest travel, taking 0.1398 minutes to traverse a backwoods road cell, is more than eight times slower than the fastest (only 0.0172 minutes/cell). Off-road travel is based on typical hiking rates under increasingly steep terrain, with the steepest class (2.2369 minutes/cell) being 130 times slower than travel on a highway. In addition, there are some locations that form absolute barriers to ground move- ment (e.g., very steep slopes, open water).