Excess sedimentation began affecting the wetland dynamics of Pine Gully in Seabrook, Texas during the first quarter of 2004. This sedimentation was sudden and became a serious problem for the dynamics of the Pine Gully wetland because the fine, well sorted, quartz rich sediments began plugging the main channel of the previously tidally dominated wetland. Progressive sedimentation has produced overbank deposits in the marine grasses, contributing to the death of wetland grasses by sediment chocking. The main purpose of this study is to determine the new source and mechanism of sedimentation in Pine Gully, document changes from sedimentation, and determine a solution to prevent future sedimentation. Sedimentation in Pine Gully and coastal areas adjacent to Pine Gully has occurred in a region that has experienced subsidence and sea level rise. The sedimentation in Pine Gully is a direct result of new and sustained sediment at the mouth of Pine Gully. These new sediments are transported into Pine Gully by displacement waves from ships moving through the Houston Ship Channel. Beach renourishment at Wright Beach, located a half mile north of Pine Gully, occurred as Pine Gully experienced sedimentation. Construction of a breakwater at the mouth of Pine Gully and subsequent removal of sediment in Pine Gully itself is ultimately the solution to revitalizing the wetland to its pre-sedimentation state. Replanting of native vegetation killed off by sedimentation is recommended and would hasten the recovery of the wetland. Documenting the effects of this unique sedimentation in Pine Gully has implications for the future. Beach renourishment or coastal projects that may contribute excess sediment to the coastline should be concerned with unintended effects they may cause. Although an historically eroding shoreline exists, the effects of excess sedimentation can be severe. A coastal study should be done before sediment is added to the shoreline to identify any areas within the sphere of influence of the project. Ecosystems determined to be within the sphere of influence by a coastal study should implement preventative measures at those locations to avoid an ecological disaster similar to that in Pine Gully.

Abstract This study belongs to one part of FATES research program, which studies the fate of terrestrial substances in Kaoping river-sea system. The task is to study the components and properties of sediments and spatial distribution of sedimentation rates off the southwest Taiwan by analyzing water content, TOC, CaCO3, grain size, P-wave velocity and radionuclides 210Pb and 137Cs in sediments. Thirty cores collected for this study were divided into three groups based on topography and they are Kaoping continental shelf, slope and canyon. The highest TOC content is 1.53 % in ORI732-ST31 and TOC content ranges from 0.20~0.93 % for the rest of sediments from other stations. The highest CaCO3 content is found in ORI732-ST18, 30, ORI779-ST1, and ST12. Most of the CaCO3 content is greater than 4% at these four stations. Probably because of the lower sedimentation rates that result in less terrestrial substances for diluting the CaCO3. In the shelf and slope regions, the distribution of grain size progressively decreases as the water depth increases. Grain size in the stations farther down the canyon, however, is coarser than those at upper canyon. It suggests that there is other sediment source for stations in the canyon in addition to the Kaoping river. The sedimentation rates derived from 210Pbex profiles range from 0.073~0.168 cm/yr in shelf, 0.033~0.670 and 0.094~0.411 cm/yr in continental slope and canyon, respectively. Sedimentation rates are all less than 0.2 cm/yr in the shelf area, but there are five stations with sedimentation rates higher than 0.2 cm/yr in the slope and canyon areas. Among the five stations, the sedimentation rate is up to 0.670 cm/yr (ORI779-ST9), suggesting that 302~822 m deep in the slope and 975~1156 m deep in the canyon are the deposition centers. In some stations, anomalously low 210Pbex activities exist in surface or sub-surface sediments, indicating that the low 210Pbex activity sediments may be typhoon-induced turbidite sediments. According to Central Weather Bureau¡¦s typhoon catalog, in the year of coring there were seven typhoons striking Taiwan. Among these typhoons, Hai-tang was the strongest one, suggesting that the turbidite sediments mentioned above were likely caused by typhoon Hai-tang. Besides, turbidite sediments appear at water depth of over 700 m, indicating episodic turbidite events are an important way to transport particles offshore.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Proefschrift--University of Utrecht. / Bibliography: p. 95-98.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisor: William E. Galloway. Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--University of Oregon, 2000. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 169-178). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (M.S.) in Geological Sciences--University of Maine, 2002. / Includes vita. Includes bibliographical references (leaves 114-119).

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