Dendro-geomorphological analyses of the Slate Creek landslide, Alaska

Abstract

Hillslopes cover much of the Earth's surface, and mass movement is one of the main ways hillslopes re-adjust their profiles in response to the changing climate. Over the next few decades, the impacts of climate changes on mass movements are predicted to be pronounced at high latitudes where temperatures are warming rapidly, permafrost is thawing, and precipitation is increasing. More frequent mass movements have the potential to threaten critical infrastructure in Interior Alaska, particularly in areas of steep slopes and discontinuous permafrost like the Alaska Range. With these concerns in mind, I investigated the dynamics of a complex landslide that is encroaching on the Parks Highway near Slate Creek along the northern front of the Alaska Range. I used dendrochronology to document the extent and timing of this landslide's movements over the past century. To quantify general and seasonal rates of movement, I analyzed aerial photography and LiDAR imagery and obtained geographical positional measurements on a network of datum points established on the landslide's surface. I sought to test the hypothesis that climate controls the activity of the Slate Creek Landslide by comparing dendrochronology and rate-of-movement data to weather records. Results indicate that different parts of the landslide are moving at rates ranging from 0.2 cm/year to 8m/year. Dendrochronological data indicate there were periods of enhanced landslide movement occurring in 1967, 1973, 1977, 1980, and 2017. It remains unclear what triggered the initiation of this landslide and what factors have controlled its recent movement rates. Possibilities include disturbance of the landslide's toe, periods of increased precipitation, a past wildfire, permafrost thaw, or some combination of these factors.