Siletz Bay is a drowned river valley filled with Holocene alluvial and estuarine sediments and is separated from the ocean by a sand spit 3.8 km in length. Since the area was settled by white man in the 1890's, the bay has apparently experienced rapid siltation, due to increased farming and logging. This along with the damming of the Siletz River sloughs has altered circulation patterns in the bay. Deflection of the Siletz River flow by the prograding Drift Creek delta has caused 105 m of erosion since 1912 on the east side of Siletz Spit. The ocean side of the spit suffers periodic erosional episodes separated by periods of accretion and dune building. The most recent and publicized erosion occurred during the winter of 1972-73 when it was feared that the spit might be breached; one partially constructed house was lost and three others were saved only by timely riprapping. A sand mining operation may have aggravated the recent erosion by disrupting the sand budget, the balance of sand additions and losses from the beach. All of the foredune on the spit has been stabilized by dune grass and much of it has been riprapped. The long term effects of stabilization and riprapping are uncertain. / Graduation date: 1975

Graduation date: 1997

Thesis (M.C.E.)--University of Delaware, 2006. / Principal faculty advisors: Nobuhisa Kobayashi and Jack Puleo, Dept. of Civil & Environmental Engineer. Includes bibliographical references.

The coastal planning has been developed in purpose of the ¡§safely¡¨, ¡§landscaping¡¨, ¡§ecology¡¨ and ¡§water affinity¡¨ in Taiwan nowadays. Moreover, the hendland bay beachs and beach nourishment have been hailed for the protection of shoreline. One of the main affection of erosion is a storm, which retreads shoreline and reduces nearshore by storm surge. This essay reports an application of 2-D SBEACH software to simulate the beach profile changes. The data of large wave tank (LWT), which tests by the Coastal Engineering Research Center (CERC), US Army Corps of Engineers, is used to calibrate the parameters by SBEACH. Then, using the results of experimentation to indicate the accuracy of model from Grosser Wellen Kanal (GWK), which tests by the University of Hannor. Finally, simulating beach profile, with a berm (height of 2.5m and width of 100m) and a slope of 1:25, is used to simulate the profile changes and analyze the results by different storm conditions from CECI. The purpose of this paper is to estimate the suitable distance of shoreline and location of bar for a beach buffer zone by SBEACH during different storm conditions. The present study confirms that the simulated results of shoreline erosion rate and the position of bar crest by SBEACH comform to the LWT and GWK experiments. The major parameters of SBEACH, the transport rate coefficient, K influences the sediment transport, coefficient for slope-dependent term, £` controls the slope of beach profile and shape of bar, the transport rate decay coefficient multiplier, Kb affects the shoreline erosion, and the landward surf zone depth, db influences the shape of berm. The result of analysis by SBEACH indicates that a constant slope beach profile changes by different storm conditions and the extent of non-dimensional shoreline retreat Xt/Lo is found in good linear relationship with deepwater wave steepness Ho/Lo. Therefore, the linear regress function is used to compute the less beach buffer zone in different storm conditions.

No description available.

A field experiment designed to test the hypothesis that infragravity and lower frequency waves influence the patterns of erosion and deposition on the beach foreshore has been carried out. The data show coherent fluctuations in the foreshore sediment level which can be related to low frequency wave motions. The fluctuations have heights of up to 6 cm with typical time scales of 8 to 10 minutes. They can be characterized in two ways: by the progression of the fluctuations up the foreshore slope (landward), and by the decrease in the RNS height of the fluctuations as they progress landward. The velocity of migration also changes as the fluctuations progress landward. Analysis of runup time series obtained by time-lapse photography concurrent with the sediment level measurements reveals long-period waves of undetermined origin at frequencies and phases which strongly suggest that the waves force the original perturbation in sediment level. In order to better understand the characteristics of these sediment level fluctuations, a numerical model of sediment transport on the foreshore has been developed. Gradients in sediment transport define erosional and depositional areas on the foreshore. Runup velocities were modeled and the results were used in the sediment transport model. The model predicts that any perturbation in foreshore elevation will progress landward while decreasing in amplitude and in velocity, thereby matching the field observations. Relationships between beach slope and the profile response clarified by this model are used to explain the initial formation of the perturbations of sediment level. / Graduation date: 1984

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Jack A. Puleo, Dept. of Civil & Environmental Engineer. Includes bibliographical references.

Thesis (Honors)--College of William and Mary, 2009. / Includes bibliographical references (leaves 45-47). Also available via the World Wide Web.

Thesis (M. LA)--Unitec New Zealand, 2009. / Subtitle partially created by cataloguer. Text in landscape format. Includes bibliographical references (leaves 88-93).

Thesis (M.S.)--Naval Postgraduate School. / Bibliography: p. 85-86.