REPEAT PHOTOGRAPHY OF LAKE MICHIGAN COASTAL DUNES: EVIDENCE OF DUNE STABILIZATION AT LOW LAKE PHASE

The coastal dunes along the shore of Lake Michigan may comprise the largest body of freshwater dunes in the world. In the past fifteen years a variety of geomorphic investigations have focused on the age and evolution of dune landscapes between Muskegon and Indiana Dunes National Lakeshore. Prior to these investigations it was generally believed that the largest (~ 60-m-high) dunes grew during low lake stages when beaches were relatively wide and sand supply was therefore high. The recent studies have suggested, through radiocarbon dating of buried soils, that growth of dunes may be more linked to high lake levels as per the perched dune model. Conversely, large dunes tended to stabilize when lake level was relatively low. These conclusions may be erroneous, however, due to the statistical uncertainties associated with radiocarbon dating.

Water levels in Lake Michigan are currently near historic lows. This low phase provides an opportunity to empirically test the validity of the perched dune model to large dunes along Lake Michigan. Repeat photography of study sites between 2000 and 2007 demonstrates that vegetation has rapidly expanded across dune exposures in the past few years, with trees even present where none were before. These observations provide good evidence that the large dunes are stabilizing during this low lake stage, which thus supports the perched dune model for dune evolution.