Analysis of Sediment Erosion and Deposition Across High Marsh and Tide Channel Sites in Wellfleet, Massachusetts.

Abstract

Bare spots associated with vegetation die-off along a tidal channel and adjacent marsh platform in the "Gut" in Wellfleet, MA area are a direct result of winter storms and increased crab herbivory. Sediment transport from bare spots and channel banks over a two-year time period are captured with the aid of repeat high-definition surveys using terrestrial laser scanning (TLS) techniques. Cross-sectional and morphometric analysis of the tidal channel reveal a statistically significant change in channel size and shape with reference to the amount of elevation change from erosion and deposition. Greater than sixty percent of the topographic changes in the marsh channel are the result of erosional processes. Cellular statistics across the marsh platform revealed less change than the channel. Depositional hotspots occur in areas of sudden wetland dieback, while erosion occurs in small depressions adjacent to the tidal channel. More than fifty percent of the marsh platform displays no change over the two-year measurement period.