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Historical Changes of Goulds Inlet, Georgia From Geospatial Analysis of Aerial Photography

Historical Changes of Goulds Inlet, Georgia From Geospatial Analysis of Aerial Photography. Rochelle Petruccelli-UWG Chester W. Jackson, Jr.-UGA David M. Bush-UWG Clark Alexander-Skidaway. Savannah . Goulds Inlet. Sea Island. Goulds Inlet Between St. Simons and Sea Islands, Georgia

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Historical Changes of Goulds Inlet, Georgia From Geospatial Analysis of Aerial Photography

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  1. Historical Changes of Goulds Inlet, Georgia From Geospatial Analysis of Aerial Photography Rochelle Petruccelli-UWG Chester W. Jackson, Jr.-UGA David M. Bush-UWG Clark Alexander-Skidaway

  2. Savannah Goulds Inlet

  3. Sea Island • Goulds Inlet • Between St. Simons and Sea Islands, Georgia • Mesotidal, spring tide range • is 3.1 meters • Small, stable inlet

  4. Sea Island spit seawall Johnson rocks

  5. A B C D

  6. Previous Work • Griffin, Martha M., and Henry, Vernon J. 1984, Historical Changes in the Mean High Water Shoreline of Georgia, 1857-1982.

  7. Griffin and Henry: Shoreline changes between 1857/60 - 1980

  8. 1924-1974 1857/60 - 1974 Griffin and Henry: Changes to St. Simons and Sea Island

  9. Griffin and Henry: Goulds Inlet system changes 1860 - 1974

  10. Goals • Assess the coastal hazards vulnerability of homes along East Beach, St. Simons Island, GA • GIS evaluation of historical behavior of Goulds Inlet • Shoreline positions • Inlet channel positions • Inlet-associated shoals • Predict future behavior of inlet system • Recommend management options

  11. Methods • Acquire historical information • Air photos • T-sheets • DOQQs • Digitize • Inlet channel • Historical shorelines • Inlet shoals • Analyze position data • Shorelines • Inlet 1963

  12. Goulds Inlet, Georgia 1942 1964 1979 1984 1993

  13. Inlet channel has migrated over time Current tidal channel location Sea Island spit seawall Previous tidal channel location(~late1800s)

  14. 76 transects, 50-meter spacing

  15. Shoreline Change Statistics • EPR = End Point Rate—Distance between oldest and youngest shorelines divided by total time elapsed (m/yr)  • AOR = Average of Rates—average of separate EPRs for all combinations of shorelines when more than two are available • LRR = Linear Regression Rate—slope of the best-fit line using all data points • JKR = Jackknife Rate—average of slopes of all points, leaving out one point each iteration • AOE = Average of Eras—change rates are calculated between each set of air photos, then averaged

  16. 1869-1933 Era 1933-1957 Era East Beach, St. Simons Island 1957-1979 Era 1979-1993 Era End Point Rates for selected eras 1993-1999 Era Accretion Erosion

  17. Shoreline Change Summary 76 transects 22 show erosion 54 show accretion 1869-2003 Era accretion erosion

  18. Inlet Shoals 1963

  19. Persistence of Inlet Shoals Green and yellow = frequent shoaling Blue = infrequent shoaling

  20. St. Simons Island Sea Island St. Simons Island Sea Island St. Simons Island Sea Island

  21. Results • Sea Island spit has steadily accreted • Northern tip of St. Simon’s has experienced long-term erosion • St. Simons East Beach has experienced net long-term accretion • Goulds Inlet appears relatively stable, though it does exhibit slow southerly migration

  22. Recommendations for homes along East Beach, St. Simons Island, GA • Major Engineering • Remove seawall, relocate inlet channel • Reorient inlet channel by dredging • Augment existing rocks, add sand, vegetate • Minor Engineering • Retreat /relocation • Retrofit buildings • Do nothing (preferred alternative)

  23. Acknowledgements • Mike Robinson, Skidaway Institute of Oceanography • Clark Alexander, Skidaway Institute of Oceanography • John Gay, St. Simons Island • John Congleton, UWG Geosciences • Jeong Seong, UWG Geosciences • Georgia Department of Transportation • University of West Georgia • Georgia Sea Grant College Program

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