High Post-Wildfire Erosion Potential for Sandia and Manzano Mountain Basins

ALBUQUERQUE, New Mexico —Basins in the Sandia and Manzano Mountains at risk for a rainfall-generated debris-flow following a wildfire are identified by a new method for estimating post-fire erosion hazards before a wildfire actually burns, according to a new U.S. Geological Survey study.

Wildfire can drastically increase the probability of debris flows, a potentially hazardous and destructive form of landsliding in landscapes that have otherwise been stable throughout recent history. This new USGS report identified watersheds with the most serious poten­tial for debris-flow hazards in the event of a large-scale wildfire and subsequent rainfall in the Sandia and Manzano Mountains, including sub-basins close to Albuquerque.

"This pre-wildfire assessment approach is valuable to resource managers because the analysis of the debris-flow threat is made before a wildfire occurs, which facilitates pre-wildfire management, planning and mitigation," said Anne Tillery, USGS scientist and author of the new report.

Simulated debris-flow probabilities, debris-flow volumes and burn probabilities were combined into an integrated hazard ranking for each sub-basin and used to identify the most hazardous basins in the Sandia and Manzano Mountains area. Five sub-basins on the west-facing slopes of the Sandia Mountains, four of which extend to the outskirts of the City of Albuquerque, are among the top two percent most hazardous for the area assessed.

"The Rio Grande Water Fund will be using the results of this study to set priorities for restoring overgrown forests,” said Laura McCarthy, director of Conservation Programs with The Nature Conservancy. “Figuring out which areas are vulnerable to damaging wildfire and post-fire flooding is necessary to protect communities and our water sources."