Delineating Post-wildfire debris flow hazards for pre-fire mitigation, Pine and Strawberry, Arizona: a FEMA 5% initiative study

Arizona has experienced a dramatic increase in area burned by wildfires during the drought of the past decade. Over 1.8 million acres of Arizona wildlands burned during the four-year period between 2002 and 2005, of which almost one million acres were burned by only five fires (Southwest Coordination Center, 2006). In addition to increased fire size, recent wildfires have burned with higher intensity, in part due to fuel loading as a result of a century of fire suppression (Schoennagel et al., 2004). High severity burns denude watersheds and may generate hydrophobic (water-repellent) soils, resulting in dramatic increases in runoff and soil erosion in upland areas. Because of these increases in post-fire runoff and erosion, fairly common rainfall events may generate sizable floods or debris flows. Although debris flows are less common than floods after fires, debris flows can be significantly more destructive than floods (Cannon et al., 2004). Post-fire hazards in burned areas are evaluated after containment of the wildfire is achieved through the Burned Area Emergency Response (BAER) program, but potential debris flow hazards typically are not assessed. Even if potential flooding and debris flow hazards are identified through the BAER process there is little time to design, plan and implement hazard mitigation efforts. ( 36 pages)Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu