Novel applications of remote sensing and GIS in mass wasting hazard assessments for two fjords of South-Central Alaska

Abstract

The fjords of South-Central Alaska are dynamic environments and host to a number of natural hazards that have not received much attention from the research community. The cities of Seward and Whittier are two of Alaska's most important marine transportation hubs, home to commercial fishing fleets, termini of the Alaska Railroad, and home to thousands of residents. This doctoral research focuses on landslides and their associated hazards in these under-studied areas. Chapter 2 involves surficial mapping of the study areas and documents the role of the underlying geologic processes that threaten the safety of people and infrastructure in the Passage Canal-Portage Valley area (including the town of Whittier), to better inform community planning, mitigation, and emergency response activities. Chapter 3 builds on the successes and lessons learned from the mapping efforts made in Chapter 2. A surficial geology and landslide inventory map were made using very high resolution orthoimagery, DEMs, and 3D models which were viewed in an immersive Virtual Reality (iVR) system. Chapter 4 examines the hazards associated with large amounts of sediment entering the alluvial fan system from further upslope. A collection of six Digital Elevation Models (DEMs) and meteorological data collected over a ten-year period were used to estimate flood-related sedimentation. Uncertainties in each DEM were accounted for, and a DEMs of Difference (DoD) technique was used to quantify the amount and pattern of sediment introduced, redistributed, or exiting the system. The study shows that the DoD method and using multiple technologies to create DEMs is effective in quantifying the volumetric change and general spatial patterns of sediment redistribution between the acquisition of DEMs. Correlations of the changes in sediment budget with rainfall data and flood events were made. During the years of average rainfall, the reaches in the corridor experienced an overall decrease in sediment load, while heavy rainfall events both saw large influx of new sediment and the reworking of existing sediment. This research is the first to collect and use high resolution data for generating digital elevation models, for using a DoD method for mapping elevation changes over time, and for using these products along with available ancillary data for a hazard assessment in these regions. This doctoral work lays out a solid foundation for further work in hazard assessment that will also guide decision-makers in the future on mitigation measures in these important population centers in south central Alaska.