COASTAL DUNE GEOMORPHOLOGY IN PJ HOFFMASTER STATE PARK ON THE EAST COAST OF LAKE MICHIGAN

The coastal dunes on the east shore of Lake Michigan vary in size, morphology and activity. Active foredunes, stabilized dune ridges, blowouts, parabolic dunes and other dune types are shaped by local winds, climate and human activity. Despite evidence of recent change, there have been few studies of contemporary dune geomorphology. This study examines the geomorphology of coastal dunes in PJ Hoffmaster State Park near Muskegon, Michigan.

One parabolic dune was studied in detail to provide reference measurements for future work that will assess its inland (eastward) progression. A topographic map of the dune was produced from a detailed ground survey using a total station. Surface conditions, vegetation and geomorphic activity were also recorded and mapped. The dune has a classic parabolic shape, rising 65 m above Lake Michigan at the crest of a single elongated blowout which funnels sand eastward to the depositional lobe. Dune advance rates may be more than a meter per year and the leading edge of the slip-face has reached a popular hiking trail.

The size, morphology, and activity of seven other large parabolic dunes within the park boundaries were examined, as well as the characteristics of the dunes westward (lakeward) of the parabolic dunes. The parabolic dunes range from unvegetated dunes with evidence of active wind flow and sand transport to mostly-stabilized dunes which have become a series of unconnected blowouts with significant vegetation cover. Many of the parabolic dunes are nested or have a complex blowout morphology between the arms of the dune. A stabilized foredune runs parallel to the shoreline along the length of the park; lakeward of the established foredune a discontinuous active foredune is growing in response to a low lake level. The current record of dune geomorphology provides a baseline for measuring dune change in coming years.