[1] Surface currents to the east of Okinawa Island were observed by using HF (highfrequency) ocean radars in August-September 1995. During that period, a typhoon passed near the observation area, and the horizontal variability of near-inertial oscillations associated with the typhoon passage was estimated. In addition, the near-inertial amplitudes and horizontal wave number vectors were estimated. These estimations showed that the near-inertial amplitude was large in the offshore area and small near the coast. The maximum near-inertial wavelength was estimated to be in the order of 1000 km, and the near-inertial wave direction was southward and changed to northwestward on 23 August in 1995. A slab model, incorporating low-frequency currents, was used to calculate near-inertial currents. It was found that the amplitude of calculated near-inertial oscillations was also large in the offshore area. Moreover, the phase-propagation direction of the near-inertial waves was southward and changed to northwestward or westward on 22 August. The growth rate obtained from the dispersion relation was large in the offshore area, where the near-inertial amplitude was large.

No abstract

CADMAS-SURF is one of the accurate numerical models that can apply to a performance-based design of maritime structure. However, there were a few application examples to irregular waves, because of the increase of computation time. Thus, a systematic study of irregular waves by CADMAS-SURF has been conducted with a cooperation of research group. The numerical simulations are conducted for transformation of irregular waves propagating a flat flume with a constant depth. The calculated spectra and representative waves are compared with those set as the target and the results of theoretical study. The characteristics of irregular waves generated by CADMAS-SURF are consistent with the existing knowledge. The modification of given spectra to make irregular waves is recommended to agree the spectra, significant wave height or significant wave period with the target at some point. The adequate selection of option parameter is required to avoid the numerical damping.

At a port located at the estuary in Japan, 800,000 m3/year of sediment is accumulated annually in navigation channel and basin. In order to consider effective countermeasures, it is necessary to elucidate sediment dynamics due to waves and tidal currents of the target port. Therefore, we are conducting a field observation of sediment transport and deposition. In addition, we have developed a numerical simulation model based on the results of the field survey for evaluated the countermeasure against the port sedimentation. We introduce the knowledge about sediment transport obtained through multiple operations.

3 正会員 いであ株式会社 沿岸・港湾事業部 沿岸解析部(〒224-0025 神奈川県横浜市都筑区早渕2-2-2) 4 フェロー会員 京都大学名誉教授(〒236-0046 横浜市金沢区釜利谷西2-33-11) 5 正会員 一般財団法人沿岸技術研究センター(〒105-0003 東京都港区西新橋1-14-2)