Browsing by Subject "shoreface"
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Item Antecedent and anthropogenic influences on the Galveston Island shoreface(2009-05-15) Pitkewicz, Jennifer LynnGalveston Island, Texas has been experiencing high rates of erosion in recent years, spawning an interest in developing complex beach management programs. However, before any effective management project can be implemented we must understand all of the processes that control the shoreface. It is only recently that scientists have begun to recognize the importance of the role that the geologic framework plays on the coastal evolution of the shoreline. In this region, it is the antecedent geology as well as the anthropogenic obstructions which are the key factors controlling the formation of the modern shoreface. This study defines the extents to which these antecedent and anthropogenic factors influence the shoreface as well as refines the geologic interpretations offshore of Galveston Island. Using sidescan sonar, CHIRP seismic sonar, multibeam bathymetry data and sediment cores, the shoreface and subsurface geology were modeled. It was determined that the thickness, extent and slope of the modern sediment in the nearshore environment is controlled by the topography of the Beaumont Clay, a consolidated clay deposited during the Pleistocene. Anthropogenic obstructions, including the Galveston Seawall, groin and jetty system, have changed the sediment transport patterns in the region and have created a system of erosion and accretion not only along the shoreline, but for the entire length of the shoreface.Item Modification and recovery of the shoreface of Matagorda Peninsula, Texas, following the landfall of Hurricane Claudette: the role of antecedent geology on short-term shoreface morphodynamics(Texas A&M University, 2006-08-16) Majzlik, Edward JamesMatagorda Peninsula is located along an interfluvial region of the central Texas coast in the northwestern Gulf of Mexico. The Pleistocene Beaumont Clay underlies the coastal plain and inner continental shelf and controls the general slope of the coast in this region. This clay surface also creates low accommodation space for the preservation of modern sediments. As a result, only a thin (1 m) layer of transgressive Holocene muddy sand extends throughout the lower shoreface. On 15 July, 2003, Hurricane Claudette (Category 1) made landfall on the peninsula. Following the storm, the shoreface was found to be an extensively eroded surface. Most obvious on this surface was an area containing numerous scour pits on the lower shoreface. These pits extended through the Holocene sediment and into the underlying Beaumont Clay. By the following July, the shoreface exhibited a relatively flat and featureless appearance. Rapid infilling of the pits was attributed to the high sediment supply to the area from converging longshore currents and by the relatively high accommodation space offered by the scoured areas. A large amount of sediment was removed from the lower shoreface where the formation of scour pits occurred. This sediment would have been available for depositionin storm layers both inshore and offshore of the scoured area. Within scour pits, accommodation space was high, resulting in sediment deposition and rapid infilling of the pits. Outside of the scour pits, accommodation space remained low and sediment deposition did not occur. Preservation potential of the sediment record on the shoreface was low and was controlled by cycles of erosion and deposition during storm events. Antecedent geology of the shoreface and the sedimentary processes occurring during and after the storm supported arguments against the assumptions used by the classic "profile of equilibrium" model. Finally, the heavily scoured surface represents a geohazard to development of nearshore regions.