1. CHANGES IN BARRIER ISLAND ENVIRONMENTS DURING SEA-LEVEL RISE
James C. Gibeaut
Bureau of Economic Geology
Jackson School of Geosciences
The University of Texas at Austin
Funding From: Galveston Bay Estuary Program, NOAA through the Texas Coastal Coordination Council, Texas General Land Office, Army Research Office, NASA
Texas A&M Sigma Xi Symposium, March 30, 2006
Talk notes:
Talk about fault
Map the upland boundary and see how much vertical change from 1950’s to 2002 – compare to SL rise
Show tide curve at time of lidar survey to illustrate the “elevation classification problem this could present.
Talk about bay shoreline erosion – we don’t have the bay shoreline data do we?
Look at areas that are within the range of elevation for marsh but are not marsh – figure out why this is – what are the other factors besides elevation that makes a marsh a marsh.

2. Texas Coast
Brief overview of shoreline types, bays vs. Gulf. Shoreline monitoring is challenging because of the length of shoreline and variety of shoreline types.

3. Regressive Barrier Island( a ) b B A Y R I E S L G U F O M X C y m r g i n d e s w l o v t f - u c h q V p k Z Q 3 1 7 P N
Regressive Barrier Island
Transgressive Barrier Island

4. Transgressive (Matagorda Peninsula)

5. Regressive (Galveston Island)

6. Color IR
Mosaic
Gulf of Mexico

7. Barrier Island Environments

8. University of Texas Airborne Topographic Lidar System (Optech model ALTM1225)

9. 1 – Meter Lidar Digital Elevation Model
Shaded relief image of digital elevation model of the study area. Banding in open-water areas is oriented parallel to the acquisition flight lines and is the result of about 0.05 m vertical error across the data swaths. The banding is only apparent on the very smooth water surface.

10. Habitat Classification Map From Color IR Photography
Data from White et al., 2002

11. Average Heights and Standard Deviations of Barrier Island Habitats

12. Change Induced by Rising Sea Level
From Brinson, Christian, and Blum, 1995

14. 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

15. Land Subsidence Relative to Pier 21, 1958 – 1978, mm/yr
Pier 21 tide gauge

16. Vertical Accretion Function
Maximum rate = m/yr
Vertical
Accretion
Function
Evidence for decreasing rate and max rate from Callaway et al., 1997

17. Shoreline Change

18. Tide Gauge Record Change Rate = 0.0064 m/yr ) m ( l e v e l e d i t h
2.5
Tide Gauge
Record
Annual Averages of
MHHW at
Pier 21, Galveston ) 2 m ( l e v e
Change Rate =
m/yr l e d i t h g i H
1.5 H i s t o r i c a l l e v e l L i n e a r f i t P r o j e c t e d l e v e l 3 - y r m o v i n g a v e r a g e 1
1900
1920
1940
1960
1980
2000
2020
2040
2060
2080
2100 Y e a r

19. Model Flow 1-year loop DEM Yes (original) No Future date reached?
Classify elevation by
environment types
Environment
grid
Yes No
Adjusted
DEM
Apply
vertical accretion
adjustment
Output
habitat grid
1-year
loop
Shoreline
change
data
Retreat
shoreline
Apply
sea level
adjustment
Apply local
subsidence
adjustment
Compute
statistics of
habitat status
Maps
Statistics
Graphs

20. Eight Analysis Areas

21. All Areas

22. All Areas

23. Eight Analysis Areas

24. Follets

25. Follets

28. Eight Analysis Areas

29. West Galveston

30. West Galveston

42. Eight Analysis Areas

43. Bolivar

44. Bolivar