Skip to main content

Backbone Post-Fire BAER

Unit Information

Coconino National Forest
U.S. Forest Service
1824 S. Thompson St.
Flagstaff, AZ 86001

USFS Shield

Incident Contact

BAER Information
Phone: 707-853-4243
Hours: 7am-7pm

Emergency Assessment of Post-Fire Debris Flow Hazards

Backbone Post-Fire BAER Burned Area Emergency Response
News – 7/15/2021

Emergency Assessment of Post-Fire Debris Flow Hazards

The Backbone BAER Assessment Team coordinated early with US Geological Survey (USGS) staff during its evaluation of the burned areas to strategically assess potential post-fire impacts to the watersheds and debris flow predicted response during damaging storm events.

From the USGS website found at “Wildfire can significantly alter the hydrologic response of a watershed to the extent that even modest rainstorms can produce dangerous flash floods and debris flows. The USGS conducts post-fire debris-flow hazard assessments for select fires in the Western U.S.  We use geospatial data related to basin morphometry, burn severity, soil properties, and rainfall characteristics to estimate the probability and volume of debris flows that may occur in response to a design storm.”

USGS used the BAER team’s soil burn severity analysis of the post-fire burned area for the Backbone wildfire to produce mapped debris flow hazard assessment predictions.  The USGS Post-Fire Debris Flow Hazard Assessment Map displays estimates of post-fire debris-flow probability, volume, and combined hazard for the areas burned by the Backbone fire.  The interactive map on the USGS website shows the potential and size of debris flows that may occur from about a 1/4 inch of rainfall over a 15-minute period.  Results from more intense rain events, ranging from about 1/2 inch per hour to 2 inches per hour, are also available from the USGS website.  The online interactive map is posted at:

Much of the burn area was estimated to have a lower level of debris-flow hazard in response to relatively common rainstorms. However, several smaller, steep, more severely burned watersheds in the central portion of the burn area as well as large parts of the Boulder Creek and Sally May watersheds were predicted to have moderate to high debris-flow hazard even from relatively common rainstorms. While predicted debris flow volumes are expected to be relatively small throughout most of the burn area for common events, a larger, higher-intensity rainstorm could trigger larger and more damaging debris flows.

USGS Fact Sheet 176-97, entitled “Debris Flow Hazards in the United States” contains information used to interpret the debris flow map and analysis that was incorporated into the BAER assessment team’s anticipated soil erosion and hydrologic response findings.  According to the USGS, “Analysis of data collected from studies of debris flows following wildfires can answer many of the questions fundamental to post-fire hazard assessments— what and why, where, when, how big, and how often?”  This information is extremely important to assist the public with increasing their safety awareness of the areas where there may be a higher increase in flooding, sediment and soil erosion, and a high probability of debris flows –- all of which are potential risks to human life, safety, and property.

SPECIAL NOTE: Everyone near and downstream from burned areas should remain alert and stay updated on weather conditions that may result in heavy rains over the burn scars. Flash flooding may occur quickly during heavy rain events be prepared to take action. Current weather and emergency notifications can be found at the National Weather Service website: