Investigation on the wave conditions and hazardous sites at the Longdong Fishing Cliffs using MIKE21-BW wave model

• Main Authors: Lan-Yu Yu, 余蘭玉
• Other Authors: Cheng-Han Tsai
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/64931982375343490033

碩士 === 國立臺灣海洋大學 === 海洋環境資訊學系 === 99 === Longdong wave cut terrace with protruding cliffs toward the ocean is located on the north eastern coast. This terrace is famous for cliff line-fishing, and numerous drowning incidents due to dangerous coastal waves have occurred here. This article used MIKE21 Boussinesq wave model (BW) to investigate coastal waves at this site. The present study first did field observations of the wave conditions on the cliff and found some spots with high waves and large run-up. BW simulations, using the wave recorded at the Longdong wave buoy, just offshore of the cliff, at the same instance as the field observations were carried out. The simulations showed that the locations with observed high waves did have large wave heights. Wave simulations using various wave conditions also showed that the outer edges and the left side (facing the ocean) of protruding cliffs have large significant wave height, resulting from wave energy concentration. Some spots are more dangerous than others, depending on the wave directions. Wave simulations also suggested that when the incident wave with significant wave height larger than 1.5 m, peak period longer than 10s, and the wave angle is normal towards the cliff, most of the cliffs are in danger of being overwhelmed by the high waves, and one should refrain from fishing on this cliff. It should also be noted that the offshore wave height and wave period can suddenly increase with wave direction also changing to normal direction towards the cliff. This situation can lead to the occurrence of drowning incidents, if the fishermen kept staying on the cliff. The sudden change of wave conditions can be the most important cause for the drowning incidents.