Spatial and temporal assessment of back-barrier erosion on Cumberland Island National Seashore, Georgia, 2011–2013

Scientific Investigations Report 2016-5071
Prepared in cooperation with the National Park Service
By:  and 

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Abstract

Much research has been conducted to better understand erosion and accretion processes for the seaward zones of coastal barrier islands; however, at Cumberland Island National Seashore, Georgia, the greater management concern is the effect that erosion is having on the resources of the island’s western shoreline, or the back barrier. Catastrophic slumping and regular rates of erosion greater than 1 meter per year threaten important habitat, historical and pre-historical resources, and modern infrastructure on the island. Prior research has helped National Park Service (NPS) staff identify the most severe and vulnerable areas, but in order to develop effective management actions, information is needed on what forces and conditions cause erosion. To this end, the U.S. Geological Survey, in cooperation with the NPS, conducted two longitudinal surveys, one each at the beginning and end of the approximately year-long monitoring period from late 2011 to early 2013, along five selected segments of the back barrier of the Cumberland Island National Seashore. Monitoring stations were constructed at four of these locations that had previously been identified as erosional hotspots. The magnitude of erosion at each location was quantified to determine the relative influence of causative agents. Results indicate that erosion is, in general, highly variable within and among these segments of the Cumberland Island National Seashore’s back barrier. Observed erosion ranged from a maximum of 2.5 meters of bluff-line retreat to some areas that exhibited no net erosion over the 1-year study period. In terms of timing of erosion, three of the four sites were primarily affected by punctuated erosional events that were coincident with above-average high tides and elevated wind speeds. The fourth site exhibited steady, low-magnitude retreat throughout the study period. While it is difficult to precisely subscribe certain amounts of erosion to specific agents, this study provides insight into the mode of erosion among sites and the interaction among factors that set up conditions that may be leading to punctuated events.

Estimates of sea-level rise were incorporated into the results of this study to project conditions that could be in place by the end of the 21st century. When using the erosion rates observed in this study to extrapolate future shoreline position, results indicate an average retreat (across all monitored locations) of 15 meters by 2050 and approximately 37 meters by 2100.

Suggested Citation

Calhoun, D.L., and Riley, J.W., 2016, Spatial and temporal assessment of back-barrier erosion on Cumberland Island National Seashore, Georgia, 2011–2013: U.S. Geological Survey Scientific Investigations Report 2016–5071, 32 p., http://dx.doi.org/10.3133/sir20165071.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments 
  • Abstract
  • Introduction
  • Purpose and Scope
  • Methods
  • Site Selection and Description
  • Back-Barrier Erosion and Causative Agents
  • Projections of Future Shoreline Positions
  • Discussion
  • Summary
  • References Cited
  • Appendix 1. Field Calibration Information From In Situ Photo-Electronic Erosion Pins
  • Appendix 2. Campbell Scientific Program Used for In Situ Monitoring Instruments  During the Back-Barrier Erosion Project at Cumberland Island National Seashore
  • Appendix 3. Campbell Scientific Wiring Diagram Used During the Back-Barrier Erosion Project at Cumberland Island National Seashore 

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Spatial and temporal assessment of back-barrier erosion on Cumberland Island National Seashore, Georgia, 2011–2013
Series title Scientific Investigations Report
Series number 2016-5071
DOI 10.3133/sir20165071
Year Published 2016
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) South Atlantic Water Science Center
Description Report: vii, 44 p. Data Release
First page 1
Last page 32
Country United States
State Georgia
Other Geospatial Cumberland Island National Seashore
Online Only (Y/N) Y
Additional Online Files (Y/N) Y