Contemporary Geomorphology of a Large Parabolic Dune on the East Shore of Lake Michigan, USA

Coastal dunes on the east shore of Lake Michigan include large parabolic dunes (30-60 m high) with varying levels of activity. This study examines the characteristics and activity of a large parabolic dune in P.J. Hoffmaster State Park, Michigan. In a summer 2008 field study, dune characteristics were investigated using a total station to map dune topography, areas of erosion and deposition, vegetation characteristics such as pioneering species or forested dune slopes, and human impacts such as trails. Using GIS, the 2008 results were compared to the results of a 2002 field study which mapped the topography of the same dune. The rate of dune advance calculated from the GIS analysis was compared to measurements at erosion pins installed at the bottom of the slipface in October 2005 and monitored through summer 2008. The dune's activity was compared to the activity of nearby dunes through analysis of air photos, site visits, and previous studies. Results show that this is an active parabolic dune rising approximately 62 m above nearby Lake Michigan. Compared to neighboring large dunes, this parabolic dune has a relatively simple morphology with a well-developed primary blowout and corresponding slipface. There is a less-developed secondary blowout on the south arm of the dune. Between 2002 and 2008, changes to the dune occurred in both the primary and secondary blowouts, with erosion from the unvegetated upper windward slopes and deposition on the forested slipfaces. Pin measurements indicate rates of slipface advance (at the primary blowout) of up to 60 cm per year. The dune is advancing over a popular park trail. A better understanding of this dune's activity will aid future management of this dynamic natural feature.