FLAGSTAFF – On May 3, Forest Service Burned Area Emergency Response (BAER) specialists, led by Brandon Waterman, completed their field data evaluation to produce the Soil Burn Severity (SBS) map for the approximately 19,075-acre Tunnel Fire.

The map and the data delineate unburned, low, moderate and high SBS categories. The BAER team assessing the Tunnel Fire determined that approximately 4,774 acres (24%) of the fire is unburned, approximately 12,285 acres (67%) have low SBS, approximately 1,421 acres (8%) sustained a moderate SBS and only approximately 11 acres (<1%) were identified as having high soil burn severity.The SBS map product is an estimate of fire effects to soils, not fire effects to vegetation. SBS characterizes fire effects to the soil surface and below ground. Fire effects to vegetation would include an estimate of vegetation mortality which does not always correlate with degree of soil burn severity.

Moderate and high soil burn severity can alter or damage physical, chemical, and biological soil properties resulting in increased runoff, erosion, and negative effects to soil productivity. These soil properties include but are not limited to hydrophobicity (water repellency), soil organic matter content, soil pore space, soil cover (effective litter), and soil structure (including grade (degree of aggregation) and type (physical form).

Changes to these soil properties determine the degree of soil burn severity. Water repellency often occurs naturally in soils and it changes as a function of fire. It is frequently discussed as a post-fire effect. Fire can increase the strength and thickness—or depth—of water repellent layers in soil, considerably affecting post-fire water runoff and possibly extending time for recovery of the burned area.

The Tunnel BAER assessment team used remote sensing imagery with field-validated soils data to produce the final SBS map. The BAER team will use the SBS map as an analysis tool to estimate post-fire erosion with subsequent sediment delivery, stream flows and debris flow probabilities. The map is also being shared with cooperating agencies.

The Tunnel Fire soil burn severity map can be downloaded at the “Tunnel Fire BAER” InciWeb site (https://inciweb.nwcg.gov/incident/8088/) as a JPEG or PDF version under the “Maps” tab.

As a reminder, The Coconino National Forest has instituted a Forest Closure Order for the area affected by the Tunnel Fire.