Lake Level Effects as Measured from Aerial Photos

Rising Lake Michigan water levels were found to negatively influence the amount of wetlands and beaches in the Straits of Mackinac area of Lake Michigan. The effects of long‐term fluctuation in water levels were determined from measurements of wetlands and beaches on seven sets of historical aerial photographs (1938–1980). Analysis of aerial photographs demonstrated a 380 acre (154 ha) difference in total wetland and beach areas at the highest lake level sampled, as compared to the total at the lowest lake level sampled, or a range of 4 ft (1.2 m). A linear model between total wetland and beach areas and water levels $(R^2=0.93)$ indicated an increase of 1 ft (0.3 m) would result in a decrease of 80 acre (32 ha) or 18% of the 439 acre (178 ha) of wetlands and beaches in the study area. This methodology, which includes measurements from historical aerial photographs, acquisition of small format aerial photographs, and determination of local hydrological conditions, was useful for quantifying change in these lacustrine wetlands.