Comparing Added Treatments and Concluding
As before, select the model change layer to evaluate flame length reduction. Now compare the original untreated landscape with this new treated landscape. What you'll really want to know is how much of an affect this added treatment of low severity wildfire, or a broadcast burn, will have compared to just the light thinning and pile burn applied earlier. You'll need to compare the first treatment to the second one to answer this.
Swipe between layers
To compare these “treatments” (default disturbance edits) on the landscape, first use the Swipe widget:
- Click Simulation Output Tools and check the boxes next to:
- "GC12 Lt Thn PileRx 1yr" the first treatment of thinning and pile burning.
- "GC12 Lt Thn PileRx 1yr Rx 1Yr" the second treatment which follows the thin with a low severity burn.
- Make sure these layers are displayed just under "shapes" toward the top of the Layer List. In this example the first three layers in Layer List are "Shapes", "Model Output: GC14 Lt Thnpilebrn 1yr Rx 1y", followed by "Model Output: GC14 Lt Thnpilebrn 1yr."
- Click the Swipe widget.
You can control the layers that appear in the Swipe widget using the box in the top right of the map that appears once the Swipe widget is clicked. The layer selected in this box is the layer that appears in the top half of the slider, and hidden on the bottom half. In this example "Model Ouptut: GC14 Lt Thn Pilebrn 1yr Rx 1yr" is selected in the Swipe box.
- Swipe between the layers and compare: In this example the light thin and pile burn is shown as the top swipe layer, followed by light thin, pile burn, and low severity wildfire (broadcast burn). Sliding back and forth and looking at the legend indicates that Flame Lengths were in fact reduced by several feet in some areas with just the addition of the Low Severity Wildfire! Next you'll want to see how the Fuel Models have changed with the addition of the Low Severity Wildfire.
Set the Layer List up again, this time opening:
- Landscape Tools.
- Select the two treatment layers.
- Make sure these layers appear on the Layer List.
- Click the Swipe widget.
Set the layers to swipe.
In comparing these two edited landscapes, as well as the Landscape Change Map earlier, you see there was a significant shift in Fuel Model between the thinning/pile burn treatment and the addition of the low severity wildfire.
Review summary reports
Next, open the Compare Summary Reports to get the full picture and make a more informed decision about what treatments should be applied to achieve the preliminary objectives.
Navigate to My Workspace and open the Fire Behavior Summary Compare Report.
The Fire Behavior Compare Reports for a modeled Light Thin/Pile Burn/Low Severity Broadcast Burn treatment show even more of a difference in pre and post-treatment fire behavior.
The Flame Length Bar Chart shows a large increase in the post-treatment acreage for lower Flame Length bins and no post-treatment acres in the higher Flame Length bins.
The table indicates the pre-treatment percentage of pixels in the >0-1 foot Flame Length bin is 1%, while post-treatment the percentage went up to 13%. Conversely, the percentage of post-treatment pixels in the 3 highest Flame Length bins is 0, indicating a significant decrease in Flame Lengths post-treatment, across the treatment area.
The Percent Difference Graph for Flame Lengths demonstrates the shift toward lower Flame Lengths post-treatment. You can see the significant positive percent difference in the >0-1 and >1-4 foot bins, while the bins correlating to higher Flame Lengths indicate a drop in the percent difference.
The Pie Charts tell the same story, plainly showing the shift to significantly lower flame lengths in the post-treatment chart.
Scroll through the rest of the fire behavior model outputs in the report. Their story is the same, significantly reduced Rates of Spread, as well as almost no Crown Fire Activity post-treatment.
Next, navigate back to My Workspace and open the Landscape Compare Summary Report.
The Landscape Compare Reports for a modeled Light Thin/Pile Burn/Low Severity Broadcast Burn treatment show quite a change in Fuel Model pre- vs. post-treatment.
From the compare bar graph, you can tell that a significant portion of the TL8 Fuel Model (Long-Needle Litter) has shifted to the GR2 (Low Load, Dry Climate Grass) and GS1 (Low Load, Dry Climate Grass-Shrub) Fuel Models, 1 year post-treatment. The table to the right confirms this quantitatively, indicating that 55% of the treatment area was comprised of a TL8 Fuel Model pre-treatment, while just 2% of the treatment area was a TL8 Fuel Model post-treatment. Conversely, none of the treatment area contained the GS1 Fuel Model pre-treatment, while post-treatment over 60% of the treatment area was comprised of Fuel Model GS1.
The Percent Difference chart reflects the shift in Fuel Model displayed by the Bar Graph and table above, clearly showing the drop in the TL8 Fuel Model, as well as the increase in the GS1 Fuel Model post-treatment.
The Pie Charts visually display these changes in Fuel Model as well.
Review the rest of the Landscape Compare Summary Report and note the changes in the various landscape characteristics. Pay particular attention to the increase in Canopy Base Height, as well as the decrease in Canopy Cover, post-treatment. This coincides with the information you see in the rest of the report, and reiterates the fact that this series of treatments will help achieve the stated objectives, which were to: reduce surface fuel loading and the overall horizontal and vertical fuelbed continuity in order to reduce the fire hazard to adjacent private land and the community of Idaho City; and return low intensity fire to fire adapted vegetation communities.
You could continue this process and model a more invasive treatment, such as heavier thinning or increased mortality from a more severe broadcast (prescribed) burn, but these results achieve your initial preliminary objectives, and are a good place to start with a project proposal for the District ID Team.
From this process, it’s clear that the expected fire behavior, given 97th percentile fire weather and fuel moisture conditions, in the identified treatment areas is much more intense than what would be considered characteristic in this frequent, but low intensity, fire regime. The reports and maps demonstrate how these proposed treatments help achieve the preliminary objectives to reduce surface fuel loading and the overall horizontal and vertical fuelbed continuity, as well as helping to return low intensity fire in these treatment areas.