SHORT-TERM VARIATIONS IN AEOLIAN DEPOSITION ON A FOREDUNE ON THE EAST SHORE OF LAKE MICHIGAN

Lake Michigan coastal dunes are dynamic landforms that are influenced by changing lake levels and seasonal wind, temperature and precipitation patterns. Since the fall of 2000, aeolian activity has been studied in a coastal dune system in P.J. Hoffmaster State Park near Muskegon, MI, on the east coast of Lake Michigan. Sand transport, erosion and deposition on an active foredune were measured with sand traps and erosion pins from October through April each year. During the second and third year of the study, wind, temperature, and humidity were recorded at an instrument tower in the study area. Other variables including soil moisture, snow-cover, ice, ground-freezing and beach width were observed and recorded during site visits.

During the October-April measurement periods, total volumes of sand added to the foredune were 4.5 m³ m^-1 in 2000-01, 5.0 m³ m^-1 in 2001-02 and 1.9 m³ m^-1 in 2002-03. Maximum deposition at some locations on the foredune crest exceeded 35 cm in 2000-01 and 2001-02, compared to 26 cm in 2002-03. This study examines the reasons why aeolian inputs to the Lake Michigan foredune in 2002-03 were less than half the amount of the previous two years.

On the Lake Michigan coast, fall and winter sand transport by wind is not solely a function of wind speed. Wet, frozen or snow-covered surfaces reduce sand transport rates, and total amounts of transport depend on the size of the area which supplies sand to aeolian processes. Over the three years of the study, beach width varied between 15 and 35 meters as the level of Lake Michigan changed. Winter conditions during the three years can be classified as generally snowy, warm, and cold respectively, but the overall condition of the winter may not be as important to sand transport as less-frequent conditions. Studies like this one are important to understanding how spatial and temporal variations in weather and lake levels affect Lake Michigan coastal dunes.