Geoscience Reference
In-Depth Information
(a)
(b)
300
200
Galveston Island
Follets Island
200
100
Case Fig. 8.1
(a) Satellite Image
showing barrier islands of the Texas
Coast. Dominant longshore drift
direction is arrowed. Galveston
Island and Follets Island are marked.
(Image from NASA Earth Science
Applications Directorate
(https://zulu.ssc.nasa.gov/mrsid/).)
(b) Long-term shoreline position
(relative to 1930) of Follets Island and
Galveston Island. Both islands have
retreated by over 200 m since 1930.
(After Morton et al. 1995.)
0
100
0
−
100
−
100
−
200
−
200
−
300
−
300
−
400
1930
1950
1970
1990
1930
1950
1970
1990
Date
Date
The study showed that sediment transfers were dominated by episodic storms that caused
near-instantaneous erosion of barrier islands. A hurricane in 1983 (Hurricane Alicia) eroded
between 50 and 70 m
3
of sediment per metre of beach from Galveston Island and lesser
amounts from Follets Island. Most of the eroded sand was transported south-west by strong
currents associated with the hurricane and was deposited on the shoreface (only 12% of the
volume lost was carried over the islands and deposited as overwash).
Post-storm recovery (Case Fig. 8.1c) took place over several years and involved phases of sand
migration onshore, bar welding to the beach, and finally dune build-up as the beach became dry
