This thesis examines the environmental conditions which led to the loss of 90%
of the natural salt marsh in Galveston Island State Park since 1930 and analyzes one
potential method to reduce future loss. Available data and recent studies suggest that
the primary factor responsible for the historic loss was the lack of a sufficient supply of
sediment to keep up with relative sea level rise. The average rate of sediment accretion
for the period from 1963 to 2006 was measured to be 0.25 cm/year based on 137Cs and
239,240Pu nuclides. This rate is about 0.4 cm/year less than the relative sea level rise of
approximately 0.65 cm/year during the same period. The marsh restoration project,
constructed in 1999 at the Galveston Island State Park, focused on reduction of wave
induced erosion and direct replacement of marsh substrate through terracing. The
restoration project did not address the potential for marsh lost to submergence.
As an alternative to geotubes or more permanent breakwater methods, a
submerged sacrificial berm constructed around the marsh is a possible approach to
address ongoing submergence. The sacrificial berm increases the available sediment
supply by allowing partial transmission of waves to create a net transport of sediment
into the marsh. In addition, the berm is designed to limit wave height in the marsh to
reduce wave induced erosion. The proposed method involves iteratively adjusting the
width and elevation of the berm top to maximize sediment transport from the berm into
the marsh. A sediment transport model is developed to quantify the increased transport
into the marsh, estimate a nourishment interval and qualitatively judge the expected
berm evolution. The Galveston Island State Park marsh was used for demonstration purposes; however, the restoration concept and method of analysis is applicable to other
marshes in Galveston Bay.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/5964 |
| Date | 17 September 2007 |
| Creators | Thomas, Robert C. |
| Contributors | Edge, Billy, Ravens, Tom |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 2516776 bytes, electronic, application/pdf, born digital |
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