CHANGES IN BARRIER ISLAND ENVIRONMENTS DURING SEA-LEVEL RISE

1. 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 CHANGES IN BARRIER ISLAND ENVIRONMENTS DURING SEA-LEVEL RISE

2. Texas Coast

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

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. Pier 21 - Galveston 180.0 160.0 140.0 120.0 100.0 Average water level (cm) y = 0.652x - 1145.6 Global ocean-level rise 80.0 2 R = 0.9436 60.0 4.36 + 2.16 = 6.52 mm/yr 40.0 20.0 Local land subsidence 0.0 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Year Relative Sea-Level Change

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

16. Maximum rate = 0.0064 m/yr Vertical Accretion Function Evidence for decreasing rate and max rate from Callaway et al., 1997

17. Shoreline Change

18. Change Rate = 0.0064 m/yr 2.5 Tide Gauge Record Annual Averages of MHHW at Pier 21, Galveston 2 ) m ( l e v e 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 Future date reached? DEM (original) 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 Compute statistics of habitat status Apply local subsidence adjustment 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