1. 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

2. Texas Coast

3. 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

4. Galveston Island

5. Matagorda Peninsula

6. Average Annual Shoreline Change Rate 1930 - 2000 and 1974 - 2000
End of Seawall
San Luis Pass

7. 2060 Projected Shoreline

8. 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.

9. Galveston Island State Park, Pre-Frances, August 8, 1998 (profile BEG-02)

10. Galveston Island State Park, Post-Frances, September 16, 1998 (profile BEG-02)

11. Galveston Island State Park, April 27, 2006 (profile BEG-02)

16. Beach/Dune Profile Translation

17. Foredune Mapping

18. Foredune Mapping
landward dune line
shoreline

19. 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

20. Barrier Island Environments

21. Total Estuarine Marsh Area
From White et al., 2004

22. 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

23. Development
1956

24. Development
1979

25. Relative Sea-Level Change
Pier 21 - Galveston
y = 0.652x R 2 =
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)
= 6.52 mm/yr
Local land subsidence
Global ocean-level rise

26. Changes Due to Relative Sea-Level Rise

29. Shoreline Change
From Gibeaut et al., 2003

30. 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

34. Projected Marsh Change

35. New Development (post geohazard mapping)

37. Geohazards Map Units
West Bay
Gulf of Mexico

39. Post Hurricane Carla, 1961

40. Area of enhanced potential
for washover
Natural protective
ridge
Storm washover paths