Analysis of Shoreline Change for Jekyll and Sapelo Islands, Georgia
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ANALYSIS OF SHORELINE CHANGE FOR JEKYLL AND SAPELO ISLANDS, GEORGIA WITH GIS TECHNIQUES by BEI TU Under the Direction of E. Lynn Usery ABSTRACT The objective of this research is to use geographic information systems (GIS) to quantify shoreline position change during 1954 and 1999 for Sapelo Island and Jekyll Island in Georgia, USA. Shorelines from multiple years were manually traced from digital raster graphics, aerial photographs, digital orthophoto quad quadrangles and a lidar image using ArcView GIS software, Version 3.3. This study showed that the northern ends of Jekyll and Sapelo islands are eroding, whereas the southern ends are accreting. Mann-Whitney test (two-tailed) indicated that the mean accretion rates and annual change rates (regardless of direction) of the two islands differed statistically during 1954-1974,1974-1993 and 1954-1999. The mean recession rates were significantly different during 1954-1974 and 1974-1993, but not so for 1954-1999. Human activity exerted a heavy influence on the shoreline change. Quantifying shoreline change provides useful data on the effects of engineering structures on erosion and is important for coastal zone management and planning. INDEX WORDS: GIS, shoreline change, Sapelo Island, Jekyll Island, lidar, coastal zone ANALYSIS OF SHORELINE CHANGE FOR JEKYLL AND SAPELO ISLANDS, GEORGIA WITH GIS TECHNIQUES by BEI TU B.E., Wuhan University, P. R. China, 2001 A Thesis Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE ATHENS, GEORGIA 2004 © 2004 Bei Tu All Rights Reserved ANALYSIS OF SHORELINE CHANGE FOR JEKYLL AND SAPELO ISLANDS, GEORGIA WITH GIS TECHNIQUES by BEI TU Major Professor: E. Lynn Usery Committee: David S. Leigh Marguerite Madden Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia August 2004 iv DEDICATION This is dedicated to my dear parents for their unconditional love and support to me. v ACKNOWLEDGEMENTS So many people have helped me in this study directly or indirectly. Although I am thankful to all, I cannot hope to give all the credit that is due. My deepest gratitude goes to my major professor, Dr. Lynn Usery, for his inspiration, invaluable advice and excellent guidance. Without his direction and help along the way the completion of my thesis would have been impossible. I would like to thank Dr. Marguerite Madden for her generous help. Her insightful suggestions always inspired me to work further on this project. My sincere appreciation also goes to Dr. David Leigh; our discussions provided me with a better understanding of the topic. I want to thank Dr. Keqi Zhang at at the Florida International University for allowing me to use the Metric Mapping ArcView extension developed by him. I appreciate the help from my good friend Roy Fenoff on my field trip to Jekyll Island. I am genuinely grateful to my family for their unconditional love, support and always being there for me. I want to thank my best friend, Amanda Jones, for her encouragements, prayers and confidence in me, and above all, for her precious friendship. Last but not least, I am thankful to God for all his blessings in my life. vi TABLE OF CONTENTS Page ACKNOWLEDGEMENTS.............................................................................................................v LIST OF TABLES....................................................................................................................... viii LIST OF FIGURES ................................................................................................................... ix, x CHAPTER 1 INTRODUCTION .........................................................................................................1 2 LITERATURE REVIEW..............................................................................................4 2.1 Previous Coastal Studies .....................................................................................4 2.2 Shoreline Mapping Techniques...........................................................................8 2.3 Shoreline Change Rate Computation Techniques.............................................11 2.4 Important Factors of Shoreline Change.............................................................13 3 STUDY SITES AND DATA SOURCES....................................................................17 3.1 Physical Setting .................................................................................................17 3.2 Data Sources......................................................................................................20 4 METHODOLOGY ......................................................................................................26 4.1 Map Projection ..................................................................................................26 4.2 Aerial Photograph Rectification........................................................................27 4.3 Delineation of Shorelines ..................................................................................28 4.4 Shoreline Registration .......................................................................................29 4.5 Shoreline Change Rate Computation ................................................................30 vii 4.6 Shoreline Change Comparison..........................................................................31 5 RESULTS ....................................................................................................................36 5.1 Map Projection ..................................................................................................36 5.2 Aerial Photograph Rectification ......................................................................36 5.3 Shoreline Registration .......................................................................................36 5.4 Shoreline Change Rate Computation ................................................................37 5.5 Shoreline Change Comparison..........................................................................37 6 DISCUSSION AND CONCLUSION..........................................................................46 REFERENCES ..............................................................................................................................58 viii LIST OF TABLES Page Table 1: Parameters of input projection and output projection......................................................32 Table 2: 1974 tide tables for Jekyll Island and Sapelo Island........................................................32 Table 3: 1993 tide tables for Jekyll Island and Sapelo Island........................................................32 Table 4: Accuracy for map projection of Jekyll and Sapelo islands..............................................38 Table 5: Accuracy for airphoto rectification of Jekyll and Sapelo islands....................................38 Table 6: Computed tidal heights for Jekyll Island and Sapelo Island at 11:30 am........................39 Table 7: Maximum and mean erosion/accretion rates, mean annual change rates of Jekyll (J) and Sapelo (S) Island during the study periods .....................................................................39 Table 8: One-Sample Kolmogorov-Smirnov test results for Jekyll and Sapelo islands................40 Table 9: Comparison of average erosion rate, accretion rate and annual change rate of Jekyll Island and Sapelo Island .................................................................................................40 Table 10: Computed tidal heights for Jekyll Island and Sapelo Island at 10:00 am......................55 ix LIST OF FIGURES Page Figure 1: Change rate equals slope of the line with EPR ..............................................................14 Figure 2: Change rate equals slope of the regression line with LR ...............................................14 Figure 3: Change rate equals averaged slope of the regression lines with JK...............................15 Figure 4: Change rate equals averaged slope of the multiple EPR................................................15 Figure 5: Sea wall on Jekyll Island, Georgia .................................................................................16 Figure 6: Sand dunes on the beach at Jekyll Island, Georgia ........................................................16 Figure 7: Jekyll Island and Sapelo Island, Georgia .......................................................................23 Figure 8: Sign of current caution on the oceanward beach of Jekyll Island, Georgia ...................24 Figure 9: Aerial photograph of the northern end of Jekyll Island..................................................24 Figure 10: Aerial photograph of the northern end of Sapelo Island ............................................25 Figure 11: Aerial photograph of the central part of Sapelo Island ..............................................25 Figure 12: Shoreline delineation of southern Jekyll Island on USGS DRG..................................33 Figure 13: Shoreline delineation of southern Jekyll Island on aerial photograph .........................33 Figure 14: Shoreline extraction from the 1999 lidar image...........................................................34 Figure 15: An example showing spine and transects construction................................................35 Figure 16: Annual shoreline change rates of Jekyll Island during the study periods