CMGL Student Featured in ASBPA NewsletterBy: Marissa DotsonCMGL undergraduate student Marissa Dotson’s article entitled “Coastal Vegetation Line Dynamics Along Mustang and North Padre Islands, Texas” was published in the American Shore & Beach Preservation Association’s Coastal Voice newsletter in the July/August 2013 issue. The article highlights Dotson’s undergraduate research on vegetation line changes on Mustang and North Padre Island. The entire issue can be accessed from ASBPA’s website here. The Texas Open Beaches Act established a mandate in 1959 allowing unobstructed access to the dry portion of Gulf-facing beaches, from the mean high water line to the vegetation line. Because beaches are not physically static, the public easement moves as the vegetation line naturally shifts landward or seaward. In recent years, the concept of rolling easements has come under intense legal scrutiny. In 2012, the Texas Supreme Court ruled in Severence v. Patterson that the easement will only shift if the vegetation line is moved through the slow process of imperceptible erosion, but not through sudden erosion due to inevitable storm activity. Unfortunately, this ruling threatens open access to a historically public natural resource and disregards natural coastal processes that affect beach morphology.
In an attempt to create a more comprehensive characterization of vegetation line dynamics, this research analyzes the historical trend of vegetation movement and the potential effects of beach maintenance on vegetation line position. Aerial photography dating from 1979 to 2012 is used to digitize vegetation lines and analyzed for rate of change and net movement along heavily-used sandy barrier islands of Mustang and North Padre Islands, Texas. This data is then compared to relative levels of beach maintenance activity along the islands to quantify the effect of beach maintenance on vegetation line movement.
Beach maintenance activities include scraping the beach with heavy equipment, stacking sand landward or seaward of foredunes, and removing sargassum. The results from this study indicate that areas of relatively high beach maintenance activity correspond with seaward shoreline and vegetation line movement because maintenance activities artificially add sand to the foredune. The artificially extended foredune becomes vegetated, extending the vegetation line seaward. In general, the shorelines and vegetation lines on non-maintained beaches are moving landward, with the exception of Mustang Island State Park—the only location in the study area where driving on the beach is not allowed. An inference can be drawn that the natural beach state promotes dune accretion and vegetation propagation, but driving is destructive to incipient dunes and vegetation. Additional details of this research will be presented at ASBPA’s 2013 National Coastal Conference in South Padre Island, Texas. |
Thursday, July 18, 2013
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