New Mexico Geological Society Annual Spring Meeting — Abstracts

Accurate landslide hazard assessment is a first step to understanding the risk that landsliding poses to people and infrastructure. Such hazard assessments critically rely on inventories of landslide occurrences, which can further be used to verify and draw out associations with environmental factors like bedrock geology and landcover, triggering mechanisms (e.g., wildfire), and probability of human impact by future landslides. The most recent state-wide landslide inventory in New Mexico was completed in 1990 and was based on aerial photography interpretation, a method that has inherent limitations related to land cover and restricted field of view. Limited updates were made in 2017 based on field mapping conducted in various locations during the intervening period. Consequently, despite best efforts, the accuracy and completeness of the current state-wide landslide inventory are questionable. Nevertheless, this inventory and related products are necessarily used in state level hazard risk assessments and for planning purposes, such as the 2023 State of New Mexico Hazard Mitigation Plan, which specifically identifies the current landslide mapping as a limitation. To demonstrate the need to address this limitation, I present a preliminary update to the current state-wide landslide inventory for an area near Taos, New Mexico mapped using recently acquired LiDAR-based bare earth digital elevation models. This high quality, high-resolution (1-meter) topographic data facilitates production of derivative products (e.g., topographic slope maps), and supports remote mapping of landslide features using modern best practices. The study area is characterized by dense forest coverage and steep topography, factors that inhibit field-based and aerial photography techniques used to construct the current landslide inventory. The city of Taos is also an important population center and recreational hub in the state, and thus unidentified landslide hazard in the surrounding area has the potential to impact people and infrastructure. Preliminary results confirm that landslide hazard is more extensive than is evident from the current landslide inventory and identifies locations where unmapped landslide features are in proximity to infrastructure. This work suggests that LiDAR-based landslide mapping provides starkly different context for understanding landslide hazard in New Mexico and justifies broader implementation of these techniques to map landslide features across the state.