Using Volumetric Estimates of Eolian Sand to Explain the Geography of Coastal Sand Dunes in Lower Michigan
Alan F. Arbogast, Ashton M. Shortridge, and Michael E. Bigsby
This study assesses the geography and volume of coastal dune sand along Lakes Huron and Michigan in Lower Michigan. Dune field extents were obtained from digital maps of critical dune area and soil parent material. Volumetric estimates were determined by establishing basal surface elevations and then calculating the average height of overlying dune deposits using digital elevation model (DEM) data within a raster GIS framework. Results indicate that ~ 1.8km3 of coastal dune sand occurs in Lower Michigan, with ~ 95% located along Lake Michigan due to prevailing westerlies. Most (~ 80%) of eolian sand is contained within 10 dune fields. Six of these fields are along the northeastern coast of Lake Michigan where they are associated with embayments and headlands, suggesting that changing shore angles and sandy bluffs are important geographical variables. Dune fields along the southeastern shore generally line the coast for greater distances and contain smaller concentrations of eolian sand that may be partially derived from debouching streams. The volumetric difference between the northeastern and southeastern of Lake Michigan may occur in part because 1) northern coastal surfaces continue to rebound isostatically, resulting in progressively younger surfaces for dune growth, and 2) erosion in the southern end of the basin has removed dune deposits..