Abstract
　This paper proposes a numerical model for the refraction computation of directional spectra due to time-varying currents, water depth and incident waves. It is a generalization of the previous models using a backward wave ray tracing technique as the computational scheme in case of steady input conditions. The model is applied to the computation of wave refraction caused by steady one-dimensional currents on a uniformly sloping beach and the validity is confirmed in comparison with the theoretical result. Then a similar computation is carried out in the case of time-varying currents to investigate the effect of time-dependency on wave transformation. Moraover, a pseudo-periodic variation of wave heights observed at the Naruto Strait with strong tidal currents is shown to be explainable qualitatively by the present model.

【キーワード】：海岸災害, 不規則波, 波浪変形計算モデル, 非定常流れ

*愛媛大学工学部海洋工学科
Department of Ocean Engineering, Faculty of Engineering, Ehime Univ.
**愛媛大学大学院工学研究科
Graduate Course of Ocean Engineering, Ehime Univ.