How To

Using Disturbance Severity

Begin by visiting the Disturbance Severity tool. There are two routes you can take to analyze a fire event: one where you upload a shapefile defining a fire boundary, and another where you draw an approximate boundary on the map.

In either case, you will provide the following information:

Park Unit

Select the park unit where the fire event occurred. Currently, Joshua Tree National Park and Mojave National Preserve are supported.

Fire Event Name

A unique name for this particular fire event.

Severity Metric

The fire severity metric to use for analysis. Three options are available:

Relativized Burn Ratio (RBR) - Recommended for low-biomass environments like the Mojave Desert. RBR normalizes severity relative to pre-fire vegetation, so a fire that completely consumes sparse desert vegetation registers as high severity even though the absolute change is small.
Relativized differenced NBR (RdNBR) - Similar to RBR but uses a different normalization approach. Useful for comparison with some federal severity products.
differenced NBR (dNBR) - Measures absolute change in vegetation reflectance. Best suited for high-biomass environments like forests. In low-biomass areas, dNBR may underestimate severity because there is less vegetation to lose.

See Methodology for technical details on how these metrics are calculated.

Date Ranges

Pre-fire and post-fire date ranges to collect imagery. We recommend 2-3 week windows before and after the fire event. Wider windows include more satellite passes but may introduce phenological bias.

Step 1 - Set analysis parameters

Fill in the park unit, fire event name, and severity metric. Click “Upload Shapefile” to upload a zipped shapefile defining the fire boundary.

Set parameters

Step 2 - Upload boundary shapefile

Select a zipped shapefile (.zip) containing your fire boundary. The shapefile should include the standard components (.shp, .shx, .prj, and optionally .dbf).

Upload shapefile

Step 3 - Set date ranges and submit

Specify the pre-fire and post-fire date ranges, then click “Process Fire Analysis” to begin processing.

Set dates

Step 4 - Review severity results and accept boundary

After processing, you will see the fire severity map displayed on the right. The interface shows two workflow steps: Boundary Refinement and Vegetation Analysis. Since you uploaded a shapefile, click “Accept” under Boundary Refinement to confirm your boundary.

Review results

Step 5 - Adjust severity thresholds (optional)

Use the Fire Severity Color Breaks panel to adjust the threshold values that define unburned, low, moderate, and high severity classes. These thresholds affect both the map visualization and the vegetation impact statistics—the breakpoints you set here are used when calculating zonal statistics for each severity class.

Adjust thresholds

Click “Apply Changes” to update the visualization.

Step 6 - Run vegetation impact analysis

Click “Analyze” under Vegetation Analysis to compare fire severity against the park’s vegetation map. This calculates how much of each vegetation community was affected at each severity level, using the threshold breakpoints you configured.

Vegetation analysis

The results table shows:

Vegetation Community - the vegetation type from the park’s vegetation map
Total Hectares - area of that vegetation type within the fire perimeter
% of Fire Perimeter - proportion of the fire area covered by that vegetation type
Severity Distribution - visual breakdown showing unburned, low, moderate, and high severity areas

Click the expand icon on any row to see detailed statistics including mean severity and standard deviation for each severity class.

Step 7 - Save or export results

You can download the vegetation impact data as a CSV file using the “Download CSV” button. To save your analysis state for later, use the “Save State” button. You can reload a previous analysis using “Upload State”.

Save state

Methodology

How To

Using Disturbance Severity

Park Unit

Fire Event Name

Severity Metric