APPLICATION OF LIDAR TO MAPPING GEOLOGIC HAZARDS ALONG GAS PIPELINES IN ALASKA

Alaska is characterized by diverse geologic environments and a wide range of geologic processes and associated hazards. Recently proposed natural gas pipelines traverse rugged terrain across the state, requiring a better understanding of the location and types of geologic hazards that could potentially impact pipeline alignments and design. However, developing information on Quaternary active faults and other geologic hazards in Alaska has proved difficult due to rugged topography, limited road access, dense vegetative cover, and inadequate aerial photography and remotely sensed imagery. Lidar digital topographic data provides a means to perform improved analysis of the landscape and facilitates efficient identification and characterization of geologic hazards in regions where other methods have been ineffective.

The Alaska Division of Geological & Geophysical Surveys (DGGS) is acquiring high-resolution lidar data within a 1-mile-wide corridor along the entire length of proposed natural gas pipeline corridors from Prudhoe Bay to the Canada border and from Delta Junction to Valdez. Here I present preliminary observations and interpretations from a subset of the new lidar data relevant to the assessment of geologic hazards. Additionally, I show several techniques that DGGS is employing to map these hazards and reveal subtle topographic features that may indicate the locations of active faults, landslides, permafrost, erosion, and flooding hazards. These techniques include slope, aspect, and surface roughness maps, longitudinal profiles, and construction of high-precision topographic maps. Data products from these analyses will be combined with DGGS’s previous Quaternary surficial-geologic and hazards mapping along the pipeline corridor in a project GIS. The analyses will be used to systematically evaluate geologic hazards over broad regions. These relatively new techniques have important implications to pipeline route selection and refinement, design, and construction in Alaska and around the world.