GIS MODELING OF SHORELINE CHANGE AT YELLOWSTONE LAKE, YELLOWSTONE NATIONAL PARK, USA

Alternating advance and recession of the northern and southern shores of the West Thumb Arm of Yellowstone Lake are documented from a 48-year time series of aerial photographs (1954, 1976, 1989, 1994, 2002). To test the hypothesis that observed changes of the Yellowstone Lake shore are modulated by caldera dynamics and lake level oscillations, a four-dimensional model of the West Thumb Arm of Yellowstone Lake was constructed utilizing Geographic Information System (GIS) software. This model uses three-dimensional digital terrain data for West Thumb Arm derived from USGS land surface elevations merged with dual frequency echo sounder data acquired from the research vessel Ozark Explorer during 2004 and 2005. Within the GIS, this three-dimensional lake basin model was varied over time using data from releveling surveys and geodetic observations (since 1992) from the Yellowstone network of continuous GPS stations as well as lake levels measured by National Park Service personnel. Modifying the 3-D lake basin model with the power and efficiency of GIS permitted testing and evaluation of shore responses to differential basin tilt, lake level oscillations, and various combinations of surface deformation/lake level in an effort to explain shoreline changes evident on aerial photographs. This modeling, along with calculated rates of bluff erosion around the lakeshore, will ultimately yield insights into the lakeshore response to geodynamic and climatological processes, and will have practical applications to resource management by the National Park Service.