The Timing of Susceptibility to Post-Fire Debris Flows in the Western United States

Abstract

Research Article| November 01, 2015 The Timing of Susceptibility to Post-Fire Debris Flows in the Western United States JEROME V. DeGRAFF; JEROME V. DeGRAFF U.S. Department of Agriculture Forest Service, 1600 Tollhouse Road, Clovis, CA 93611 Search for other works by this author on: GSW Google Scholar SUSAN H. CANNON; SUSAN H. CANNON U.S. Geological Survey, Box 25046, DFC, MS 966, Denver, CO 80225 Search for other works by this author on: GSW Google Scholar JOSEPH E. GARTNER JOSEPH E. GARTNER BGC Engineering, 1299 Washington Ave., Suite 280, Golden, Co 80401 Search for other works by this author on: GSW Google Scholar Author and Article Information JEROME V. DeGRAFF U.S. Department of Agriculture Forest Service, 1600 Tollhouse Road, Clovis, CA 93611 SUSAN H. CANNON U.S. Geological Survey, Box 25046, DFC, MS 966, Denver, CO 80225 JOSEPH E. GARTNER BGC Engineering, 1299 Washington Ave., Suite 280, Golden, Co 80401 Publisher: Association of Environmental & Engineering Geologists First Online: 02 Mar 2017 Online Issn: 1558-9161 Print Issn: 1078-7275 © 2015 Association of Environmental & Engineering Geologists Environmental & Engineering Geoscience (2015) 21 (4): 277–292. https://doi.org/10.2113/gseegeosci.21.4.277 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JEROME V. DeGRAFF, SUSAN H. CANNON, JOSEPH E. GARTNER; The Timing of Susceptibility to Post-Fire Debris Flows in the Western United States. Environmental & Engineering Geoscience 2015;; 21 (4): 277–292. doi: https://doi.org/10.2113/gseegeosci.21.4.277 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract Watersheds recently burned by wildfires can be susceptible to debris flow, although little is known about how long this susceptibility persists and how it changes over time. We use a compilation of 75 debris-flow response and fire-ignition dates, vegetation and bedrock class, rainfall regime, and initiation process from throughout the western United States to address these issues. The great majority (85 percent) of debris flows occurred within the first 12 months following wildfire, with 71 percent occurring within the first 6 months. Seven percent of the debris flows occurred between 1 and 1.5 years after a fire, or during the second rainy season to impact an area. Within the first 1.5 years following fires, all but one of the debris flows initiated through runoff-dominated processes, and debris flows occurred in similar proportions in forested and non-forested landscapes. Underlying geologic materials affected how long debris-flow activity persisted, and the timing of debris flows varied within different rainfall regimes. A second, later period of increased debris flow susceptibility between 2.2 and 10 years after fires is indicated by the remaining 8 percent of events, which occurred primarily in forested terrains and initiated largely through landslide processes. The short time period between fire and debris-flow response within the first 1.5 years after ignition and the longer-term response between 2.2 and 10 years after fire demonstrate the necessity of both rapid and long-term reactions by land managers and emergency-response agencies to mitigate hazards from debris flows from recently burned areas in the western United States. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.