ABSTRACT This field guide discusses the dune types and processes, ecology, and geomorphic history of the largest freshwater dune systems on the southeastern shore of Lake Michigan. From north to south, stops include P.J. Hoffmaster State Park, Gilligan Lake/Green Mountain Beach Dune, Saugatuck Harbor Natural Area, and Grand Mere and Warren Dunes State Parks, Michigan. All of the sites are low, perched transgressive dune complexes. Moving from the lake inland, the typical dune complex in this area consists of incipient foredunes, an established foredune ridge, a parabolic dune complex, and a back-dune ridge complex. All stages of ecological succession are typically present in the larger dune complexes. Surface changes in Lake Michigan dunes are driven by spatial gradients in sand flux, which, in turn, are determined by a complex interaction among wind dynamics, vegetation patterns, and preexisting topography. Surface change patterns are modified by seasonal effects, with the majority of sand transport being associated with strong storms in the autumn, winter, and early spring. Sand can be temporarily stored in niveolian deposits during the winter, leading to oversteepened slopes, which collapse during the spring thaw. Current dune complexes largely formed during and after the rise in lake levels to the Nipissing high lake level, ca. 4.5 ka. Broad fields of relatively low dunes developed during the lake-level drop following the Nipissing high. Beginning with the rise to the Algoma high lake level, ca. 3.2 ka, the lakeward edges of these fields were episodically reworked, forming large parabolic dune complexes. A period of widespread dune stability formed the Holland Paleosol, a spodic inceptisol. Dune growth and migration resumed prior to European settlement of the area and continues today. Foredune complexes grow wider and higher during periods of low lake levels, but narrow during periods of high lake level due to scarping at their lakeward edges.

The evolution of Great Lakes coastal dunes includes long-term trends and short-term variations. This study explores multi-year, interannual and seasonal patterns of change as a Lake Michigan foredune responds to variations in lake level, weather and surface conditions. The study site is an active foredune in P.J. Hoffmaster State Park on the east coast of Lake Michigan. Foredune changes, local conditions and processes were monitored from 2000 to 2012 with repeated ground surveys, erosion pins, microclimate measurements, and observations of surface conditions. Additional weather and lake-level data were obtained from regional sources. Study results show a trend of foredune growth during the multiyear study period, with interannual and seasonal variations in the rates and spatial patterns of dune growth. At the scales of investigation, relationships between dune change and variables could not be quantified, but patterns of foredune change and influential variables were identified. The greatest amounts of erosion and deposition took place during the autumn and winter when strong winds were the most frequent, but storm conditions, vegetation changes, precipitation, snow, and ground freezing affect the availability of sand for transport by wind. Study results suggest that event-scale research is needed for understanding interactions between variables and the foredune, but mesoscale studies such as this one are crucial for identifying cumulative patterns of dune change and the role that events play in the larger scale patterns of dune evolution.

Remote sensing and geospatial analysis techniques allow for better understanding of dynamic landforms such as sand dunes. Our study investigated to what extent geospatial analysis of historic aerial photographs could be used to detect changes in dune activity over time at three Lake Michigan parabolic dunes in western Michigan, USA. We georeferenced historic aerial photographs, dating from 1938 to 2008, and then used edge-detection in remote sensing software ERDAS Imagine to distinguish bare sand from vegetated areas. The photos were then imported into the geographic information system ArcGIS, where they were reclassified and vectorized to create bare-sand outlines. Further analysis in ArcGIS allowed us to determine the changes over time to the bare-sand areas and the movement of the edges between bare sand and vegetation along the central axis of the dunes. Results show significant variability in each dune's bare-sand area during the study period, although only small increases in bare-sand area were recorded from the beginning to the end of the study. An indicator of continuing dune activity is the eastward advance of the inland edge of each bare-sand area from 1938 to 2008. Understanding changes in dune activity, especially long-term variation, through utilizing these geospatial technologies offers new insights and opportunities for research in the ongoing study and management of west Michigan dunes.