Developing Treatment Alternatives - Colville National Forest Example

Section 7– 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 :

1. Click Simulation Output Tools widget and check the boxes next to:
2. “Watershed 20 Thn Pburn 10 yr” the first treatment of thinning and pile burning.

3. “Watershed 20 Thn 10 yr Rx 1 yr” the second treatment, which follows the thin with a low-severity burn.

   

4. In Layer List, check or uncheck the layers until only your landscapes of interest are displayed. In this example, “Watershed 20 Thn Pburn 10 yr” is shown on top, and “Model Output: Watershed 20 Thn 10 yr Rx 1 yr” is shown on the bottom.
5. Click the Swipe widget .

6. 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.

   

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 the 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:

1. Landscape Tools widget .

2. Select the two treatment layers.

   

3. Make sure these layers appear on the Layer List widget .
4. Click the Swipe widget .

5. 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 36%, while post-treatment, the percentage went up to 92%. The table also indicates that the percentage of post-treatment pixels were drastically decreased for all of the Flame Length categories but the >0-1 feet.

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 foot bins, while the bins correlating to higher Flame Lengths indicate a drop in the percent difference.

The pie charts tell the same story, showing the shift to significantly lower flame lengths post-treatment.

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 TU5 Fuel Model (Very High Load, Dry Climate Timber-Shrub) has shifted to GS1 (Low Load, Dry Climate Grass-Shrub). The table further confirms this quantitatively, indicating that 50% of the treatment area was comprised of a TU5 Fuel Model pretreatment, while just 4% of the treatment area was a TU5 Fuel Model post-treatment. Conversely, 1% of the treatment area contained the GS1 Fuel Model pretreatment, while post-treatment, 63% 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 TU5 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 close 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 justifies the fact that this series of treatments will help achieve the stated objectives for this North Selkirk study area.

Conclusion

Based on Forest Plan direction and the CFLRP proposal guidelines, the preliminary results of this study show that we are meeting our objectives for the North Selkirk Project Areas, which are to:

• Recommend hazardous fuels treatments that can occur through this project to: Reduce the risk of uncharacteristic wildfire and/or re-establish or maintain low-severity fire regimes; reduce surface fuel loading and the overall horizontal and vertical fuel bed continuity to reduce the fire hazard to adjacent private, Tribal, and State land; and return low intensity fire to fire adapted vegetation communities.
• Locate areas where our actions will be most effective.
• Evaluate what type of treatment will help achieve these objectives.
• Describe why the treatment acres were chosen. Why here? Why now? What risk assessment did you use to identify these areas, e.g. wildfire hazard potential map or regional risk assessment, forest-wide risk assessment, etc.
• Demonstrate the need for treatment, both quantitatively and spatially, to members of your Forest Natural Resources Staff Officer and district interdisciplinary (ID) team.

This study was modeling more extreme fire behavior, given 97th percentile fire weather and fuel moisture conditions used, than the low-intensity/moderate-severity fire the study area typically sees in this portion of the Colville National Forest. This will help to justify future treatments during increasingly dry and hot sea-sons predicted for the future. You have set the foundation for a good report to give to your FLT and, if necessary, can go back and test out different treatment methods, such as a heavier thinning or increased mortality from a more severe broadcast burn.

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