Relative Coastal Change-Potential Assessment of Glacier Bay National Park and Preserve

A change-potential index (CPI) was used to map the relative coastal change-potential of the shoreline to future sea-level fluctuation within Glacier Bay National Park and Preserve (GBNPP) in southeastern Alaska. The CPI ranks the following in terms of their physical contribution to coastal change: geomorphology, regional coastal slope, rate of relative sea-level change, historical shoreline change rates, mean tidal range and mean significant wave height. The rankings for each input variable were combined, and an index value calculated for 1-minute grid cells covering the park. The CPI highlights those regions where the physical effects of sea-level and coastal change might be the greatest. This approach combines the coastal system's potential for change with its natural ability to adapt to changing environmental conditions, yielding a quantitative, although relative, measure of the park's natural susceptibility to the effects of sea-level variation. The CPI provides an objective method for evaluation and long-term planning by scientists and park managers. The CPI was developed from a Coastal Vulnerability Index (CVI) typically applied to coastlines experiencing long-term sea-level rise. The CPI is modified from the CVI and applied to the emergent coast of GBNPP to understand the limits of applying this type of assessment method in a variety of sea level settings. GBNPP consists of sand and gravel beaches, rock cliffs, calving glaciers, mudflats, and alluvial fans. The areas within GBNPP that are likely to be most susceptible to coastal change as a result of sea-level change are tidewater glaciers and outer coast shorelines of unconsolidated sediment where wave energy is highest and the regional coastal slope is shallowest.