Abstract
A geographic information system (GIS) was used to introduce and test a new method for quantitatively characterizing topographic change. Borrowing from classic Newtonian mechanics, the concept of a body’s center of mass is applied to the geomorphic landscape, and the barrier island environment in particular, to evaluate the metric’s potential as a proxy for detecting, tracking and visualizing change. Two barrier islands along North Carolina’s Outer Banks are used to test this idea: Core Banks, uninhabited and largely-undeveloped, and Hatteras Island, altered by the presence of a protective dune system. Findings indicate that for Core Banks, the alongshore change in the center of mass is in accord with dominate littoral transport and wind conditions. Cross-shore change agrees with independent estimates for the island migration rates. This lends credence to our assertion that the mass center metric has the potential to be a viable proxy for describing wholesale barrier migration and would be a valuable addition to the already-established ocean shoreline and subaerial volume metrics. More research is, however, required to demonstrate efficacy.
Highlights
This research introduces a new quantitative metric for characterizing coastal change: the system center of mass
The high water line (HWL) is defined as the position of the land/water interface at the time of the last high tide prior to survey [10] and is demarcated on the beach by a line, differentiating darker toned wetted sand from the intertidal zone and the lighter toned drier sands located on the supra tidal beach [2,4,7]
As is evidenced by the difference surface for Core Banks seen in Figure 5, beach retreat and overwash were significant along the barrier island in the post-Irene data
Summary
This research introduces a new quantitative metric for characterizing coastal change: the system center of mass. Much previous research associated with coastal change has relied on the ocean shoreline and changes in the shoreline’s position ([1,2,3,4,5,6,7,8,9]). The most common datum used to represent this shoreline has been the high water line (HWL). The HWL is defined as the position of the land/water interface at the time of the last high tide prior to survey [10] and is demarcated on the beach by a line (the wet/dry line), differentiating darker toned wetted sand from the intertidal zone and the lighter toned drier sands located on the supra tidal beach [2,4,7]. The HWL has been superseded by the tidally referenced mean high water (MHW)
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