Fire Lookout Tower Coverage in the
San Bernardino National Forest
Embedded Files
Ryan Grammer
GIST 602A
Abstract
This project will assess the coverage of fire lookouts in the San Bernardino National Forest. Using a Digital Surface Model (DSM), we can conduct viewshed analysis from the lookout towers that are spread throughout the San Bernardino National Forest. The DSM accounts for trees and buildings, so that we get an accurate result of what a viewer would be able to see while looking for smoke from a fire. The analysis will finish with an assessment on how many acres of land are able to be seen from the lookout towers, along with recommended sites for new lookout towers to improve coverage. The recommended sites will need to be accessible, and span as much uncovered area as possible. The result will include the visible acreage that each new lookout tower would add.
This project will assess the coverage of fire lookouts in the San Bernardino National Forest. Using a Digital Surface Model (DSM), we can conduct viewshed analysis from the lookout towers that are spread throughout the San Bernardino National Forest. The DSM accounts for trees and buildings, so that we get an accurate result of what a viewer would be able to see while looking for smoke from a fire. The analysis will finish with an assessment on how many acres of land are able to be seen from the lookout towers, along with recommended sites for new lookout towers to improve coverage. The recommended sites will need to be accessible, and span as much uncovered area as possible. The result will include the visible acreage that each new lookout tower would add.
Introduction
Fire lookout towers are crucial to firefighting efforts. There are 6 lookout towers in the San Bernardino National Forest, which covers 823,816 acres of land, and has 5 designated wilderness areas. There used to be 7 lookout towers, but unfortunately, one of the towers burned in the Fairview Fire of September 2022. These lookout towers in the San Bernardino National Forest are staffed by volunteers, who look for smoke plumes and relay the information to firefighters. Since the staffers are looking for smoke plumes, and not detailed objects, this project will not take into account visibility range based on the size of the study area. The study area will take into account the entire San Bernardino National Forest area, which is broken into two parts. The northern section spans from the west side of the Cajon Pass all the way to the east side of Big Bear, and extends south to the San Gorgonio Pass. The northern section has 4 towers. The southern section is comprised of the community of Idyllwild and surrounding areas, extending south covering the San Jacinto Mountains. The southern section contains 2 towers.
Fire lookout towers are crucial to firefighting efforts. There are 6 lookout towers in the San Bernardino National Forest, which covers 823,816 acres of land, and has 5 designated wilderness areas. There used to be 7 lookout towers, but unfortunately, one of the towers burned in the Fairview Fire of September 2022. These lookout towers in the San Bernardino National Forest are staffed by volunteers, who look for smoke plumes and relay the information to firefighters. Since the staffers are looking for smoke plumes, and not detailed objects, this project will not take into account visibility range based on the size of the study area. The study area will take into account the entire San Bernardino National Forest area, which is broken into two parts. The northern section spans from the west side of the Cajon Pass all the way to the east side of Big Bear, and extends south to the San Gorgonio Pass. The northern section has 4 towers. The southern section is comprised of the community of Idyllwild and surrounding areas, extending south covering the San Jacinto Mountains. The southern section contains 2 towers.
San Bernardino National Forest boundary and fire lookout tower locations (US Forest Service)
Viewshed Analysis
We will conduct a viewshed analysis of the area, using the Digital Surface Model (DSM) as our input raster and the fire lookout towers as the observer features. This analysis will determine the raster surface locations visible to the observer points. In other words, this analysis will show how much of the area the volunteers will be able to see when manning the tower. As mentioned previously, we will not be using a maximum distance that the viewer will be able to see. We will assume that there is good visibility while the staffers are looking for smoke. We will account for the height of the towers by using the OFFSETA parameter. This will ensure that we are getting the most accurate representation by moving the line of sight higher (since the lookout towers are off of the ground). Each tower had a different height, which was estimated by myself as there was no data on tower height. Luckily, I live right next to one of the towers and was able to get the height of that tower to compare other towers against.
Morton Peak, August 2023
Digital Surface Model of San Bernardino National Forest and surrounding areas (ALOS Global Digital Surface Model). DSM values are in meters.
Viewable areas from the lookout towers. Areas with darker colors have more towers that can see that area.
This map shows the total area of land visible by at least 1 lookout tower. We can now use this to calculate the percentage of National Forest land that is visible by a fire lookout.
The output of this tool produces the area of the polygon in a field. We can now compare this number to the area of the entire national forest, 823,816 acres. We find that combined, the 6 fire lookout towers cover 36.2% of the total area of the San Bernardino National Forest.
We can use the Calculate Geometry tool in ArcGIS Pro to calculate the area of the polygon. With our Areas Visible by At Least 1 Tower layer as the input raster, we create a new Area field, calculated with the geodesic area of the polygon. Of units of area will be US Survey Acres.
Finding New Tower Locations
There are 3 sites we will analyze to determine the best area to place a new fire lookout tower. The first site sits atop Sugarloaf Mountain, in the northern section of the San Bernardino National Forest. The second site is on top of Thomas Mountain, in the far southeast section of the national forest. Finally, the third site we will look at is Red Mountain. There used to be a lookout tower here, but it was destroyed in the Fairview Fire in September 2022. We will compare the viewshed analysis of each site against each other, and determine the area that the tower would add to the coverage.
This map shows the total area of land visible by at least 1 lookout tower, including the Sugarloaf Mountain tower.
This map shows the total area of land visible by at least 1 lookout tower, including the Thomas Mountain tower.
This map shows the total area of land visible by at least 1 lookout tower, including the Red Mountain tower.
Conclusion
We used viewshed analysis in order to calculate how much area can be viewed from existing fire lookouts in the San Bernardino National Forest. We found that the existing structures provide coverage of 298,102 acres, or 36.2% of the forest. Three potential sites were picked out for a new fire lookout tower. The three locations included Sugarloaf Mountain, Thomas Mountain, and Red Mountain. Adding the fire lookout tower to Sugarloaf Mountain increased the coverage by 45,919 acres, or 5.6%. This brings the total area covered to 344,021 acres, or 41.8%. Although this area provided more coverage to the forest, it was the worst out of the three locations in accessibility. Adding the fire lookout tower to Thomas Mountain increased the coverage by 1,902 acres, or 0.2%. This brings the total area covered to 300,004 acres, or 36.4%. Even though this lookout was on one of the higher peaks, the coverage it produced was already covered by existing lookouts. Rebuilding the fire lookout tower on Red Mountain increased the coverage by 34,316 acres, or 4.2%. This brings the total area covered to 332,418 acres, or 40.6%. We can present these findings to the US Forest Service to have them take a look at our analysis, and choose which lookout they would like to build.
References
United States Forest Service
ALOS Global Digital Surface Model
ArcGIS Pro
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