A SCHEME FOR EVALUATING THE IMPACT OF DEVELOPMENT ON THE GEOMORPHIC AND ECOLOGIC PROCESSES OF LAKE MICHIGAN’S COASTAL DUNES

Lake Michigan’s coastal dunes are highly valued for their natural beauty and diverse ecological communities. However, they face increasing development pressures because of this setting. Our current understanding of geomorphic and ecologic processes in the dunes was used to develop a scheme to evaluate the impact of housing development on the coastal dunes. The scheme uses a two-part decision-making flowchart and decisional criteria to assess impact. The first part evaluates the dune’s physical processes in three categories: dune mobility, erosion by gravity, and pavement effects. Increased or decreased dune mobility is evaluated by assessing elimination or creation of bare spots and changes in wind pattern. Potential erosion by gravity is evaluated by assessing the degree and type of vegetation on the slopes and the steepness and amount of foot traffic on those slopes. The second part evaluates the development’s impact on the type and number of ecological communities and the species composition within those communities. Five development scenarios with different dune/ecology settings, house/road layouts and densities were evaluated. The amount of dune mobility, and, therefore, the amount of sand burial, especially in open dune areas, decreased with development. Increases in erosion were negligible and pavement effects occurred only in scenarios with large parking lots. Ecologically, early pioneer and sensitive species which are dependent on sand burial were lost due to the resulting dune stability from development. Ecological changes in the back dunes were not as pronounced as these dunes have little to no dune mobility and are vegetated with later successional communities on their leeward and windward sides. Therefore, building on these dunes does not change the sand burial, and consequently, the ecological community as in the larger parabolic dunes. The distance connecting similar ecological communities increased with development, possibly decreasing the likelihood of that community’s existence. Overall, this method provides a useful method for assessing the impact of one development scenario versus another in different coastal dune settings. However, the scheme was found to be more applicable for evaluating impact in the open dunes, especially large parabolic dunes, than in the forested, back dunes.