A COMBINED FIELD AND LIDAR MAPPING APPROACH TO CHARACTERIZING GEOLOGIC HAZARDS: NATURAL GAS PIPELINE CORRIDOR PRUDHOE BAY TO ANCHORAGE, ALASKA

The Alaska Division of Geological & Geophysical Surveys (DGGS) is conducting a phased, systematic evaluation of geologic hazards along a proposed natural gas pipeline alignment between Anchorage and Prudhoe Bay, Alaska. The route traverses remote and diverse geologic terrain and presents significant challenges for pipeline routing and design due to active geologic processes including landslides, debris flows, faulting, solifluction, and flood scour. Pre-project geologic hazards assessment is a critical input parameter to pipeline route refinement, design, and construction. An investigative approach that combines traditional field mapping with remote sensing technological advances, such as LiDAR, and ArcGIS data processing technologies has become the preferred industry standard.

Here we present geologic hazard observations from our office LiDAR evaluation and helicopter-supported field work between the Yukon River and Prudhoe Bay conducted during summer 2013. Our preliminary results indicate that the region between the Yukon River and the Middle Fork Koyukuk River is characterized by relatively gentle slopes, shallow bedrock, and widespread solifluction. From the upper Dietrich River to Galbraith Lake, including Atigun Pass, active processes such as creeping frozen talus, debris flows, rock falls, snow avalanches, and slush flows are widespread and present significant hazards to pipeline construction. Seasonal stream icings and flood erosion along the Sagavanirktok and Dietrich Rivers will also require special route considerations. Our map compilation is currently in progress and will include a Quaternary geologic strip map on a LiDAR base with overlays depicting specific locations of geologic hazards and field observations. When combined with the results from our studies to the south, our geologic hazards assessment will encompass the entire ~1,100 km proposed route across the state.