Browsing by Subject "Galveston Island"

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Beach and Vegetation-Line Changes at Galveston Island, Texas: Erosion, Deposition, and Recovery from Hurricane Alicia
(1984) Morton, Robert A.; Paine, Jeffrey G.
On August 18, 1983, Hurricane Alicia crossed the Upper Texas Gulf Coast and caused extensive property damage, especially along West Beach of Galveston Island. Aerial photographs taken before and after Alicia, along with field measurements made during the first post-storm year, provide a basis for determining nearshore changes associated with a major storm and for predicting potential beach recovery. Alicia caused substantial landward retreat of both the shoreline and the vegetation line. Retreat of the vegetation line ranged from 20 to 145 ft and averaged 80 ft. Erosion was generally greatest near the Sea Isle and Bay Harbor subdivisions, where storm processes were most intense; beach erosion generally decreased away from San Luis Pass, which is near the site of storm landfall. Because erosion was so severe, surface elevations were lowered as much as 4.5 ft and many Gulf-front houses were undermined and exposed on the beach after the storm. Alicia eroded several million cubic yards of sand from West Beach. About one-tenth of that sand was deposited on the adjacent barrier flat as a washover terrace. Washover penetration was greatest to the east of the storm's eye and along developed shoreline segments. The remaining eroded beach sand was deposited offshore as shoreface bars or as storm deposits on the inner shelf. The shoreface deposits promoted rapid forebeach accretion during the first post-storm year; at the same time, the backbeach elevation remained about 3 ft lower than before the storm, and the natural post-Alicia vegetation line remained essentially unchanged. Recovery of the vegetation line 1 year after the storm was insignificant mainly because the depth of beach erosion exceeded the depth of root penetration, thus eliminating plants from some areas that were densely vegetated before the storm.
Geologic History, Depostional Envirnoment, Processes, and Hydology of Galveston Island, Texas
(1997) Garner, L. E.
Galveston Island is a very young geologic feature compared to the Earth's age of approximately 4.5 billion years. Estimates suggest that Galveston Island and other Texas barrier islands began forming as submerged bars no more than 4,500 to 5,500 years ago, based on radiocarbon dating of shells (Fisk, 1959). The following descriptions of development history, present shoreline conditions, and processes and environments have been modified from various sources including LeBlanc and Hodgson (1959), Bernard and others (1970), Fisher and others (1972), Morton (1974), McGowen and others (1977), Weise and White (1980), and Paine and Barton (1989). The origin of barrier islands has been the subject of debate, with different processes or combinations of processes shaping and modifying them. These processes depend on variables such as sediment source, type, and supply, rate and direction of relative sea-level changes, basin shape, continental shelf slope, currents, waves, and tides. Three of the most discussed theories of barrier-island origin include development from an offshore shoal or submerged sandbar, development by spit accretion resulting from longshore drift, and development by drowning of the area landward of mainland beach sand ridges (Wanless, 1974). One possible explanation for the origin of Galveston Island is that it developed from offshore shoals, with later growth aided by spit accretion. The offshore shoals might have originally been mainland beach ridges submerged during a rise in sea level. All three processes may have played a role in the island's origin, with different segments of the island undergoing different processes at varying rates during their development.