FROZEN DEBRIS LOBES – CHARACTERIZING A POTENTIAL GEOLOGIC HAZARD ALONG THE DALTON HIGHWAY, SOUTHERN BROOKS RANGE, ALASKA

Frozen debris lobes are elongated, slow-moving landslides of frozen soil, rock, and debris. As part of geologic hazards investigations along Alaska’s major infrastructure corridors, the Alaska Division of Geological & Geophysical Surveys (DGGS), in conjunction with UAF, is conducting a study of the lobes in close proximity to the Dalton Highway, Trans Alaska Pipeline System (TAPS) and proposed natural gas pipeline corridor between Wiseman and Chandalar Shelf in the southern Brooks Range. This region is characterized by steep terrain, active slope movement, and continuous permafrost. Repeat imagery and previous investigations indicate that some debris lobes are moving rapidly while others lack evidence of significant recent movement.

The primary goal of this study is to develop a means of classifying the potential geologic hazard of frozen debris lobes. This assessment is being conducted using multi-date remotely-sensed imagery and oblique photography, repeat differential GPS surveys, and multi-year geologic field observations. As part of our work we are measuring the surface rate and direction of movement of eight of these debris lobes. These data will assist us in predicting future movement, including the potential for increased movement of lobes that are currently less active. Here we present information from our preliminary classification scheme, including distance of the features from the Dalton Highway, rate of movement, slope, aspect, and size of the debris lobe and catchment area. Additionally, we discuss other parameters important for geohazard classification of the lobes. Information and results from our investigations will be important for decision-making related to long-term maintenance of the Dalton Highway and TAPS, and will be useful in planning for potential future development such as a proposed natural gas pipeline.