A Comparison of Sable Island Dune Morphology using 1988 and 2009 Profile and Digital Data

English Abstract:

The dunes of Sable Island can be categorized into four physiographic regions: the west spit, the main body, the wide flat beaches on the south part of the island including the plain of former Wallace Lake, and the east spit. Five profiles were measured using a theodolite and stadia rod in 1987 and 1988 across the island to define its basic morphology and dimensions. Using 2009 digital images and data similar profiles were digitized to determine changes that have occurred in the dune geomorphology over the twenty-year period. A summary of the results is outlined in this paper. In addition the dune morphology and a classification of the dunes, based on physiographic processes, vegetation cover, and morphology is presented.

The morphology of the dunes is variable, with elevation increasing toward the east, and width of the dune belt changing along the length of the island according to variations of width of the beaches and the Sandy Plain. In some areas the twenty plus years have resulted in remarkably little change in the profile of the dunes across the island. In other areas, there has been significant erosion and redistribution of sediment resulting in an overall decrease of the dune elevations. The unvegetated dunes can be classified as primary (dunes that develop as a result of wind action and the movement of sand over a uniform surface) or secondary (dunes that involve the deposition of sand on or behind pre-existing obstacles that slow wind speed in its lee). Vegetated dunes may be primary, secondary, or tertiary, depending upon the type of vegetation, the rate of change, and stability of the formation.