Browsing by Subject "Coastal Erosion"
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Item Conceptual Design and Physical Model Tests of a Levee-in-Dune Hurricane Barrier(2014-12-04) West, Nicholas AllanIn an effort to protect the Greater Houston Metropolitan Area from hurricane storm surge damage, four Levee-in-Dune concepts are studied as part of the Ike Dike project. The Ike Dike is a proposed hurricane surge barrier developed by Dr. William Merrell at Texas A&M University at Galveston and is based on best practices developed by the Dutch. The project would span 62 mi including a levee system along the Galveston and Bolivar coasts, and a channel barrier across Bolivar Roads. This design study includes a homogeneous sand dune, and three dunes that each incorporate different protective cores: an armorstone revetment core, a clay levee core, and a concrete T-Wall core. The concepts undergo physical model tests that subject them to conditions that simulate 100-year storm damage caused by both surge and waves. Dune and beach morphology for each concept is measured through laser profiling techniques, and each concept is evaluated based on calculated erosion and accretion, as well as design considerations including cost. Wave conditions are measured by capacitance gauges at several locations. The Clay-Core and T-Wall concepts proved to be the most effective barriers against hurricane storm surge and wave protection based on their endurance during testing.Item Radar interferometry for monitoring land subsidence and coastal change in the Nile Delta, Egypt(2009-05-15) Aly, Mohamed HassanLand subsidence and coastal erosion are worldwide problems, particularly in densely populated deltas. The Nile Delta is no exception. Currently, it is undergoing land subsidence and is simultaneously experiencing retreat of its coastline. The impacts of these long-term interrelated geomorphic problems are heightened by the economic, social and historical importance of the delta to Egypt. Unfortunately, the current measures of the rates of subsidence and coastal erosion in the delta are rough estimates at best. Sustainable development of the delta requires accurate and detailed spatial and temporal measures of subsidence and coastal retreat rates. Radar interferometry is a unique remote sensing approach that can be used to map topography with 1 m vertical accuracy and measure surface deformation with 1 mm level accuracy. Radar interferometry has been employed in this dissertation to measure urban subsidence and coastal change in the Nile Delta. Synthetic Aperture Radar (SAR) data of 5.66 cm wavelength acquired by the European Radar Satellites (ERS-1 and ERS- 2) spanning eight years (1993-2000) have been used in this investigation. The ERS data have been selected because the spatial and temporal coverage, as well as the short wavelength, are appropriate to measure the slow rate of subsidence in the delta. The ERS tandem coherence images are also appropriate for coastal change detection. The magnitude and pattern of subsidence are detected and measured using Permanent Scatterer interferometry. The measured rates of subsidence in greater Cairo, Mansura, and Mahala are 7, 9, and 5 mm yr-1, respectively. Areas of erosion and accretion in the eastern side of the delta are detected using the ERS tandem coherence and the ERS amplitude images. The average measured rates of erosion and accretion are -9.57 and +5.44 m yr-1, respectively. These measured rates pose an urgent need of regular monitoring of subsidence and coastline retreat in the delta. This study highlighted the feasibility of applying Permanent Scatterer interferometry in inappropriate environment for conventional SAR interferometry. The study addressed possibilities and limitations for successful use of SAR interferometry within the densely vegetated delta and introduced alternative strategies for further improvement of SAR interferometric measurements in the delta.