The characteristic of shoreline response to cyclic tidal change

Abstract

The responses of the shoreline change to cyclic tidal changes were investigated by the spectral analysis using FFT method and a multivariate autoregressive model. The shoreline data set were obtained for 25 years at Hazaki Oceanographical Research Station (HORS) facing the Pacific Ocean. The power spectrum densities showed shoreline changes with a period of 14.76 days, which is the spring-neap cycle of the tide. The relative power contribution analysis showed the tidal range affects the shoreline change rate as the main factor of 14.76 days cyclic variability, and it was indicated the mechanisms are due to the effects of the seawater percolation and the groundwater effluent by the difference between the water table and the tidal level. I̲580土木学会論文集B2(海岸工学) ，Vol. 68，No. 2，2012

Tide level in time and frequency domains at Dili port: Characteristic feature of a Lorentz oscillator

“…For simplicity, we took one (average) frequency for the semidiurnal and dirnurnal peaks. At lower frequencies, in addition to these two peaks, we need another 3rd component (one-year periodicity) (Banno, Kuriyama 2012), since the |H(f)| 2 takes a constant value, without the 3rd component. Overall fitting of the Lorentz oscillator, including the 3rd constituent, to the practical data is reasonably good.…”

“…It is shown that the tide levels are dominated Tide level in time and frequency domains... by four major gravitational constituents from the sun and the moon (M2, S2, K1, O1) and tide level dynamics is replicated well by the Lorentz-type resonance (Wooten 1972). The FS shows two principal peaks (diurnal and semidiurnal) (Ro 2007;Stewart 2008) and another constituent (one year), together with a 1/f-like characteristics at higher frequencies (Banno, Kuriyama 2012;Kogan 2008). It is also shown that the histogram of the tide level observed in time domain is approximated to be a Gaussian distribution function.…”

“…The tide level should have time-to-time variations (time domain), involving periodic cycles (Banno, Kuriyama 2012;Kleinhans et al 2017;Pugh 1996) due to gravitational actions. Meteorological effects such as atmospheric pressure may induce a complexity in the tide level.…”

“…Another approach is to obtain a frequency spectrum (FS) in frequency domain (FD) (Franco 1997;Marone et al 2013). The Fourier Transform (FT) is also a popular technique to obtain an FS (Banno, Kuriyama 2012).…”