SPATIAL AND TEMPORAL CONSIDERATION FOR CALCULATING SHORELINE CHANGE RATES IN THE GREAT LAKES BASIN

Abstract

Accurate long-term shoreline change rates are required for a wide range of shoreline studies and coastal zone management applications in the Great Lakes Basin. However, the literature on methods, techniques for quantifying source errors, guidelines for data acquisition, and new approaches is focused primarily on the sandy coastlines of the eastern and gulf coasts of the United States. Therefore, a comprehensive shoreline change investigation was completed for Ottawa and Allegan Counties, Michigan to investigate issues specific to the fresh water shorelines of the Great Lakes. A detailed spatial database was developed that included 79 km of continuous top of bank and dune crest lines for five temporal periods. Over 70,000 erosion transects were generated and analyzed with customized ArcGIS tools for the sandy and cohesive shore types found in the two counties. Significant spatial and temporal variability in the transect measurements were observed for both shore types. Based on the results, a series of detailed recommendations are provided for selecting historical sources of positional data, minimizing sampling errors by selecting an appropriate transect spacing, considering lake level impacts, and the influence of the bluff failure cycle on recession rates.