Characterization of Coastal Drift-Cell Sediment Processes Effecting the Restoration of the Southern Lake Michigan Shoreline.

Abstract

Hard structures along the southern shore of Lake Michigan restrict natural longshore sediment transport, destabilizing the shoreline, and dissecting the coast into localized shoreline reaches. A geometric design was used to sample (n = 590 nodes) at nine shoreline reaches near the Indiana Dunes National Lakeshore to characterize existing sediment in the offshore and onshore zones. Cluster Analysis grouped shoreline sites into two clusters. Factor Analysis showed that 35 % of the sand fractionation's cumulative variance across all sites was explained by an increased loading on medium sand (0.250 mm) with a corresponding decrease loading on small pebbles (4.750 mm), and an additional 30 % of the cumulative variance was explained by a negative loading on very fine sand (0.075 mm). Individual clusters showed that 43 % of the cumulative variance within cluster one could be explained by increased loadings on fine and medium sand (0.149-0.250 mm) with a corresponding negative loading on small pebbles (4.75 mm). An additional 22 % of the cumulative variance was explained by the positive loading on coarse sand (0.850 mm). Cluster two was explained by a single factor (62 % cumulative variance) highlighting an increased loading on small pebbles and coarse sand, and decreased loadings on medium to very fine sand. Principal component analysis showed that sediment characterization of the swash zone provided the best explanation of between site variance.