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Emergency Assessment of Lake Post-Fire Debris Flow Hazards

The Forest Service (USFS) Burned Area Emergency Response (BAER) assessment team coordinated early with US Geological Survey (USGS) staff during its evaluation of the Lake Fire burned area to strategically assess potential post-fire impacts to the watersheds and predicted debris flow response during damaging storm events.

From the USGS website found at https://landslides.usgs.gov/hazards/postfire_debrisflow/:

“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 area burned by the Lake Fire to estimate post-fire debris-flow hazards, including the likelihood of debris flow (in %), potential volume of debris flow, and combined relative debris flow hazard. These predictions are made at the scale of the drainage basin, and at the scale of the individual stream segment. The USGS Post-Fire Debris Flow Hazard Assessment estimates convey these hazards for the Lake burn area. 

The online interactive map is posted at (click on the button at the top right corner of the map to show different predictions according to storm estimates):

https://landslides.usgs.gov/hazards/postfire_debrisflow/detail.php?objectid=302