Potential postwildfire debris-flow hazards—A prewildfire evaluation for the Jemez Mountains, north-central New Mexico

Abstract

For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit http://www.usgs.gov or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit http://store.usgs.gov Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. AbstractWildfire can substantially increase the probability of debris flows, a potentially hazardous and destructive form of mass wasting, in landscapes that have otherwise been stable throughout recent history. Although the exact location, extent, and severity of wildfire or subsequent rainfall intensity and duration cannot be known, probabilities of fire and debris-flow occurrence for given locations can be estimated with geospatial analysis and modeling. The purpose of this report is to provide information on which watersheds might constitute the most serious potential debris-flow hazards in the event of a large-scale wildfire and subsequent rainfall in the Jemez Mountains. Potential probabilities and estimated volumes of postwildfire debris flows in both the unburned and previously burned areas of the Jemez Mountains and surrounding areas were estimated using empirical debris-flow models developed by the U.S. Geological Survey in combination with fire behavior and burn probability models developed by the U.S. Forest Service.Of the 4,998 subbasins modeled for this study, computed debris-flow probabilities in 671 subbasins were greater than 80 percent in response to the 100-year recurrence interval, 30-minute duration rainfall event. These subbasins ranged in size from 0.01 to 6.57 square kilometers (km 2 ), with an average area of 0.29 km 2 , and were mostly steep, upstream tributaries to larger channels in the area. Modeled debris-flow volumes in 465 subbasins were greater than 10,000 cubic meters (m 3

Estimating post-fire debris-flow hazards prior to wildfire using a statistical analysis of historical distributions of fire severity from remote sensing data

“…However, direct prediction of fire severity and associated metrics (i.e. dNBR and soil burn severity) and potential debris-flow hazards for future wildfires is an infrequently explored topic in the scientific literature (Tillery et al 2014;Haas et al 2016;Tillery and Haas 2016).…”

“…Few efforts to estimate potential debris-flow hazards before the occurrence of fire (Stevens et al 2011;Lancaster et al 2014;Tillery et al 2014;Haas et al 2016;Tillery and Haas 2016) have been attempted. Stevens et al (2011) used the presence of vegetation cover as an indicator of fire severity.…”

“…Tillery et al (2014) describe an approach for pre-fire prediction of debrisflow hazards by combining fire simulation models (Finney 2006;Finney et al 2011) with an older generation of models of debris-flow hazard estimation (Cannon et al 2010) to estimate the potential likelihood and volume of post-fire debris flows in New Mexico. Although this approach, also used by Haas et al (2016) and Tillery and Haas (2016), provides useful information such as burn probabilities, it is limited in its applicability for debris-flow prediction using current modelling equations for two reasons. First, the fire simulation models used in these analyses are labour-intensive and require a thorough understanding of wildfire processes and associated variables.…”

Before the fire: Assessing post-wildfire flooding and debris-flow hazards for pre-disaster mitigation

“…We intend to use this methodology on two upcoming pre-fire assessments of post-fire hazards in Arizona. While several studies have assessed the likelihood of post-fire debris flows (Elliott et al, 2011;Tillery et al, 2014;Tillery and Haas, 2016;Staley et al, 2018), to our knowledge there are no pre-fire assessments of post-fire hazards that also model the potential flood and debris-flows to identify downstream risk zones. We used several models, which presented their own challenges, to assess the hazards and combined the results to delineate downstream planning-level risk zones.…”

Return on investment from fuel treatments to reduce severe wildfire and erosion in a watershed investment program in Colorado

“…The crown fire activity output was classified as surface fire (i.e., no crown fire), passive crown fire (i.e., torching), and active crown fire. These classes were used as a proxy for low, medium, and high burn severity, respectively (e.g., Tillery and Haas, 2016). Potential fire behavior was simulated in FlamMap for the entire study area and is representative of extreme fire behavior.…”