With the changing perceptions in coastal engineering in recent time, creation of bay beach for recreation by combining artificial headlands with nourishment has become one of the favorable options for mitigating erosion and shore protection in several foreign countries advanced in coastal engineering. To achieve this goal, hydraulic model tests and numerical simulations have been applied for the planning and design of stable bay beaches. While using the latter approach, numerical computation includes four major components, these being the waves, topography changes, flow field and sediment transport. This study utilizes the so-called Modified Hsu3D model developed by Serizawa et al. (1996) and Kumada et al. (2002) in Japan for the bathymetry within a static equilibrium bay beach defined by Hsu and Evans (1989). This model enables the direct calculation of bottom bathymetry within a static bay without using not only iterative numerical steps for wave transformation and current distribution, but also the continuity equation for total sediment transport. The results of this simplified approach can be used to estimate the distribution of erosion and accretion within a static bay, hence, suitable for pre-assessment of an artificial beach nourishment project.
Prior to applying the Modified Hsu3D model to a bay beach undertaken in this study, sensitivity tests are performed on the setting of several key parameters associated with this model, such as limiting slope on land , limiting slope in the water , height of the berm , alignment angle at downdrift of the bay beach, and wave incident angle . The verification results are then adopted to compare with that reported in Serizawa et al. (2000), as well as to investigate the effects of each parameters on the accuracy of the modeling, in order to enhance the reliability of this model and the setting of the parameters. Finally, the Modified Hsu3D model is applied to simulate the changes in the shoreline and bathymetry for the Sizihwan Bay in Kaohsiung, under the action of normal incident waves during summer monsoon.
This study also takes the advantage of the Modified Hsu3D model to explore the effect of oblique wave incidence on the deviation of downdrift control point of a static bay, in order to assist the prediction of downdrift control point for beach changes on an artificially nourished bay beach. The results reveal that the downdrift control point does not shift, under normal incident waves with different for the breaker. On the other hand, under oblique wave action within from the external boundary line of 20 m depth offshore of a bay beach comprising sediment 0.2~0.5 mm, the offset of point (i.e., and coordinates from the original origin) versus wave incident angle can be established. By establishing a regression equation between and versus , the result can be used to assist the determination, more precisely without guess work, on locating the downdrift control point of a bay beach, while working on the MEPBAY (Klein, et al., 2003) on computer screen to assess its stability.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0814112-200726 |
| Date | 14 August 2012 |
| Creators | Chen, Hsin-an |
| Contributors | Wen-Juinn Chen, Ching-Piao Tsai, Rong-Chung Hsu |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0814112-200726 |
| Rights | unrestricted, Copyright information available at source archive |
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