GALVESTON ISLAND GEOHAZARDS MAP James C. Gibeaut Bureau of Economic Geology Jackson School of Geosciences The University of Texas at Austin City of Galveston March 8, 2007
Texas Coast
Barrier Island Cross Section Today Wetland Upland Island Core Protective Ridge Beach/ Dune Bay Gulf Future Wetland Future Beach/Dune After 60 Years of Sea-Level Rise and Erosion Protective Ridge Wetland Island Core Wetland Upland Upland Beach/ Dune
Galveston Island
Matagorda Peninsula
Average Annual Shoreline Change Rate 1930 - 2000 and 1974 - 2000 End of Seawall San Luis Pass
2060 Projected Shoreline
The next slides are from the BEG02 profile location at Galveston Isl The next slides are from the BEG02 profile location at Galveston Isl. State Park.
Galveston Island State Park, Pre-Frances, August 8, 1998 (profile BEG-02)
Galveston Island State Park, Post-Frances, September 16, 1998 (profile BEG-02)
Galveston Island State Park, April 27, 2006 (profile BEG-02)
Beach/Dune Profile Translation
Foredune Mapping
Foredune Mapping landward dune line shoreline
Barrier Island Cross Section Today Wetland Upland Island Core Protective Ridge Beach/ Dune Bay Gulf Future Wetland Future Beach/Dune After 60 Years of Sea-Level Rise and Erosion Protective Ridge Wetland Island Core Wetland Upland Upland Beach/ Dune
Barrier Island Environments
Total Estuarine Marsh Area From White et al., 2004
Causes of Wetland Loss Development/Land Use Global Sea-Level Rise Land Subsidence Topographic/Morphology Effects Sediment Deficit Marsh Edge Erosion by Waves and Currents
Development 1956
Development 1979
Relative Sea-Level Change Pier 21 - Galveston y = 0.652x - 1145.6 R 2 = 0.9436 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Year Average water level (cm) 4.36 + 2.16 = 6.52 mm/yr Local land subsidence Global ocean-level rise
Changes Due to Relative Sea-Level Rise
Shoreline Change From Gibeaut et al., 2003
Model Flow 1-year loop DEM Yes (original) No Future date reached? Classify habitat types according to elevation Habitat grid Yes No Adjusted DEM Apply vertical accretion adjustment Output habitat grid 1-year loop Shoreline change grid Retreat shoreline Apply global sea level adjustment Compute statistics of habitat status Apply local subsidence adjustment Maps Statistics Graphs
Projected Marsh Change
New Development (post geohazard mapping)
Geohazards Map Units West Bay Gulf of Mexico
Post Hurricane Carla, 1961
Area of enhanced potential for washover Natural protective ridge Storm washover paths