AVALANCHE AND LANDSLIDE EVENT HISTORY OF AN AVALANCHE CHUTE, ROCK CREEK VALLEY, MONTANA USING DENDROGEOMORPHOLOGY

Snow avalanches are one of the most common geomorphic events occurring in mountainous areas and represent a hazard to human life and property. More data for past incidents are necessary to better estimate risk and evaluate drivers of avalanche activity, especially where historical records are lacking. One way to obtain these data is through evidence found in the tree-ring record, which can be used to reconstruct past geomorphic events. Here, we use multiple lines of evidence from the tree-ring record to evaluate past avalanche and landslide history in the Rock Creek Valley of Red Lodge, Montana, a popular tourist destination and ski town. We developed two Douglas fir (Pseudotsuga menziesii) chronologies, one located along the edge of an existing avalanche chute, and the other located nearby as a control chronology to remove the common climate signal and isolate tree growth response to geomorphic changes. We found that the chute-edge and control chronologies showed similar growth patterns over the studied period 1600-2021 CE. The identified traumatic growth responses in the chute-edge chronology, that would indicate avalanche and landslide events, occurred at low frequencies in any given year. These results suggest that the avalanche history of this chute over the past 400 years is defined by low-magnitude, mid-to-high frequency events, which are confined to the chute. We did not find strong evidence for a large avalanche event over the study period, and it is likely that the event that first formed the avalanche chute occurred more than 400 years ago.