The aim of this study is to investigate the characteristics of the directional spreading when waves propagate into the shallow water zone, North-West in Taiwan. Water elevation data from 3 ADCPs (Acoustic Doppler Current Profiler) deployments during 15 Jan – 1 Feb (2011); 26 May – 22 Jun (2011) and 21 Feb – 16 Mar (2012) were recorded and used to calculate the directional spreading. The three experiments were in Yongan observation field (the 1st at 2 stations; the 2nd at 3 stations; and the 3rd at 2 stations). The Extended Maximum Likelihood Method (EMLM) was applied in this study by DIWASP toolbox to estimate the spreading parameters smax and σmin. The variation of smax and σmin will describe the variation of directional spreading. In frequency domain, the directional spreading parameters show opposite results in different deployments. The directional spreading in the 1st and 2nd deployments do not follow the refraction law while the 3rd one does. In the time domain, the variation of spreading parameters reveals the semi – diurnal oscillations. The comparison between directional spreading and other factors (significant wave height, tidal elevation and current speed) show the dependency of directional spreading on the variation of tidal current in the wave-current interaction.The aim of this study is to investigate the characteristics of the directional spreading when waves propagate into the shallow water zone, North-West in Taiwan. Water elevation data from 3 ADCPs (Acoustic Doppler Current Profiler) deployments during 15 Jan – 1 Feb (2011); 26 May – 22 Jun (2011) and 21 Feb – 16 Mar (2012) were recorded and used to calculate the directional spreading. The three experiments were in Yongan observation field (the 1st at 2 stations; the 2nd at 3 stations; and the 3rd at 2 stations). The Extended Maximum Likelihood Method (EMLM) was applied in this study by DIWASP toolbox to estimate the spreading parameters smax and σmin. The variation of smax and σmin will describe the variation of directional spreading. In frequency domain, the directional spreading parameters show opposite results in different deployments. The directional spreading in the 1st and 2nd deployments do not follow the refraction law while the 3rd one does. In the time domain, the variation of spreading parameters reveals the semi – diurnal oscillations. The comparison between directional spreading and other factors (significant wave height, tidal elevation and current speed) show the dependency of directional spreading on the variation of tidal current in the wave-current interaction.
