Joint 118th Annual Cordilleran/72nd Annual Rocky Mountain Section Meeting - 2022

Paper No. 9-25
Presentation Time: 8:30 AM-6:00 PM


SMITH, Kailee, Geosciences, Fort Lewis College, 1000 Rim Drive, Durango, CO 81301 and HARVEY, Jonathan, Fort Lewis CollegeGeosciences, 1000 Rim Dr, Durango, CO 81301-3911

August 4th- 5th, 2021 near the small town of Metlakatla, Alaska, a landslide blocked the major road which connects the town to the ferry terminal. When the ferry terminal is blocked by a landslide, access to essential goods is heavily affected. Despite the sensitivity of the residents to such disruptions, there have been no systematic efforts to map mass wasting hazards in the area. Here we present results from an effort to make a hillslope hazard map for the area of Annette Island on which the town of Metlakatla resides.

We analyzed topography from lidar data collected in 2016 and 2018 along with geologic maps, precipitation information, and the presence of recent failures to categorize the landscape into zones of varying hazard. Preliminary results show that despite the steep, glaciated topography of the mountainous island, evidence for mass wasting events appears to be limited to shallow landslides and debris flows. These events tend to not be limited to a single type of bedrock, and are found on steep forested slopes along the flanks of U-shaped valleys. While analyzing the lidar data the absence of large deep-seated slumps which are sometimes common in very mountainous setting, suggests that the rocks on this island are relatively strong, and there is a lack of substantial quaternary deposits that drape the local topography.

The results of this work will inform land managers on the island about the possibility of disruption from future mass wasting events. Results may be applicable to similar landscapes that are mostly devoid of quaternary deposits. The results of making a hillslope hazard map will give the residents of Metlakatla a sense of where these mass wasting events happen, and where potential landslides could occur