Coastal Sediment Transport Patterns off Southern Taiwan

• Main Authors: Yu-chiao Yang, 楊玉皎
• Other Authors: James T. Liu
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/bj6uf4

碩士 === 國立中山大學 === 海洋地質及化學研究所 === 95 === Abstract Water-born sediments can be transported from land to the ocean. Subsequently, waves and currents influence the sediments in their transport processes and distribution, leading to the change of the nearshore morphology and bedforms. The purpose of this study is to analyze the coastal sediments transport patterns in southern Taiwan. Two major approaches are used in this study. One is a statistical method called McLaren Model and it’s derivative Transport Vector, and another is in situ process-response observation. McLaren Model uses three granulo-metric parameters to analyze net sediment transport vectors in coastal area near the Tsengwen River mouth and Kaohsiung Harbor. Transport Vectors represent the time-averaged trends. The another method is to make in situ observation on the Kaoping continental shelf. Between December 12 and December 28, 2004, an instrumented tetrapod was deployed with an upward-looking ADCP and two LISST-100s. Another downward-looking ADCP was mounted at 2 m above bed (mab). Water samples were pumped at 1 and 0.5 mab hourly on December 13, December 20 and December 27 for suspended sediment concentration (SSC) analysis. The echo intensity (EI) can reflect the SSC. The volume concentration of thirty-two grain sizes were observed by LISST-100, so we can transform the volume concentration to suspended sediment concentration by linear correlation equation. The residual sediment transport patterns for the north of Tsengwen River are directed towards the north-west along the coastline, and the sediments around the Tsengwen River mouth are transported offshore in a radial pattern. The transport directions of sediments north of Kaohsiung Harbor are also directed towards the northwest along the coastline and southeastwards south of the harbor. The observed SSC fluctuations on Kaoping continental shelf are dominated by waves and currents. The cross-correlation of EI with current shear velocity is better than with other shear velocities. The results indicate that the SSC fluctuations are dominated by currents. In this area, the net sediment transport is northwestward, in which the amount of grain-size of 63-250μm (very fine sand and fine sand) is the greatest. This indicates that very fine-grained and fine-grained sediments are more easily transported by currents.