EVALUATION OF SURFACE CHANGE ON FROZEN DEBRIS LOBES - DALTON HIGHWAY, SOUTHERN BROOKS RANGE, ALASKA

The Alaska Division of Geological & Geophysical Surveys (DGGS), in conjunction with the University of Alaska Fairbanks (UAF), is engaged in ongoing study of frozen debris lobes (FDLs)—slow-moving landslides of frozen soil, rock, and debris—in order to assess their potential geologic hazard. These features occur in a region characterized by steep terrain, active slope movement, and continuous permafrost in the southern Brooks Range north of Wiseman, Alaska. Several FDLs are in close proximity to the Dalton Highway, Trans Alaska Pipeline System (TAPS), and a proposed natural gas pipeline route, all located in an important land corridor connecting Alaska’s North Slope to the interior and all points south.

We are currently processing and analyzing overlapping, very high resolution, near-vertical aerial photographs collected for several FDLs in June and August 2013 and 2014 in order to: 1) quantify surface change over time; 2) better understand the overall character of the flows and their source basins; and 3) develop a geohazards classification that will be useful for planners and engineers to evaluate and mitigate potential impacts of these features. We will present results from this work and discuss ongoing field investigations, including measurement of surface movement and evaluation of the geologic characteristics of the FDLs and their source basins, and highlight our study of the spatial variability of lobe surface movement. Surface morphologies and field measurements indicate variable movement rates on FDLs, which we can identify and quantify using the new high-resolution aerial photography. Based on our initial comparison of photographs taken in June and August, 2014, we are able to identify areas of significantly increased material mobilization, likely in response to the wet summer season.