Item: SPATIAL EXTENT OF FORESTED AVALANCHE TERRAIN IMPACTED BY WILDFIRE ACROSS THE SAWTOOTH NATIONAL FOREST
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Title: SPATIAL EXTENT OF FORESTED AVALANCHE TERRAIN IMPACTED BY WILDFIRE ACROSS THE SAWTOOTH NATIONAL FOREST
Proceedings: International Snow Science Workshop Proceedings 2023, Bend, Oregon
Authors:
- Zachary Miller [ U.S. Geological Survey, Northern Rocky Mountain Science Center, West Glacier, MT, USA ]
- John Sykes [ USDA Forest Service Chugach National Forest Avalanche Center, Girdwood, AK, USA ] [ Geography Department, Simon Fraser University, Burnaby, BC, Canada ]
- Megan Guinn [ USDA Forest Service Chugach National Forest Avalanche Center, Girdwood, AK, USA ]
- Ben VandenBos [ USDA Forest Service Sawtooth Avalanche Center, Ketchum, ID, USA ]
- Scott Savage [ USDA Forest Service Sawtooth Avalanche Center, Ketchum, ID, USA ]
- Erich Peitzsch [ U.S. Geological Survey, Northern Rocky Mountain Science Center, West Glacier, MT, USA ]
Date: 2023-10-08
Abstract: Forest structure is a major driver of mountain snowpacks and avalanche occurrence. Healthy forests can reduce the incidence of dangerous slab avalanches, slow avalanches when in motion, shorten their runout distances, and act as a safety buffer for backcountry users, infrastructure, and transportation corridors. Since 1984, wildfire area in the seasonal snow zone of the western United States has increased by 70% throughout the seasonal snow zone, creating significant changes to avalanche prone mountains and their connected communities. A major unknown is the impact a reduction of forested area due to forest fires will have on avalanche occurrence. We hypothesize increased potential for avalanching in forested areas impacted by wildfire. Reduced tree cover may make previously heavily forested terrain more susceptible to avalanching. Increases in the size of avalanche start zones, paths, and runouts due to forest fires may increase the destructive size of avalanches and create cascading ecological effects within the adjacent forested terrain. Forest fires may therefore increase the likelihood of avalanche release, resulting in further loss of tree cover and increased avalanche area as well as decreased protection for human infrastructure. In this study, we quantify avalanche area changes before and after the Ross Fork wildfire (2022) in Sawtooth National Forest, Idaho, USA. We utilized satellite imagery, a digital elevation model and historical fire spatial data to quantify and characterize avalanche area changes within the fire perimeter using the Auto-ATES workflow (Sykes et al., 2022). We found decreases in forest coverage that contributed to widespread increases in potential avalanche release areas, avalanche tracks, and potential runout zones throughout the study area as well as the creation of new potential avalanche release areas and a substantial decrease in non-avalanche connected terrain within the fire perimeter. These preliminary findings help inform avalanche and snow safety professionals as well as land managers working in wildfire-prone forested areas about potential post-wildfire changes in avalanche terrain.
Object ID: ISSW2023_P1.24.pdf
Language of Article: English
Presenter(s): Zachary Miller
Keywords: avalanche and wildfire, avalanche mapping, avalanche-forest
Page Number(s): 272 - 279
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