The Effects of Offshore Wave Energy Flux and Longshore Current Velocity on Medium-Term Shoreline Change at Hasaki, Japan

Abstract

The relationships between medium-term shoreline fluctuations, offshore wave energy flux and longshore current velocity were investigated on the basis of data sets from 1987 to 2001 (15 years). In this analysis, the spectral density of the data was calculated, and the frequency components from the investigated period (15 years) to 1000 days were recomposed and defined as the medium-term fluctuation. A multiple linear regression analysis was performed to evaluate the associations between the medium-term fluctuations of shoreline change rate and that of the major dependent variables, which are the offshore wave energy flux and the longshore current velocity. The results suggested that a medium-term fluctuation of the shoreline change rate at the field was affected by both the medium-term fluctuations of the offshore wave energy flux and the longshore current velocity at approximately the same rate. The fluctuation range of the medium-term shoreline fluctuation was nearly the same range of the seasonal shoreline fluctuation, i.e. approximately 20 m. This indicates that for beach management, not only seasonal shoreline fluctuation but also medium-term shoreline fluctuation is needed to be considered.

Forecasts of seasonal to inter-annual beach change using a reduced physics beach profile model

“…Spectral densities at higher frequencies may correspond to complex cyclonic wave climate and individual cyclonic events. Annual cycles agree well with the annual cyclic beach change recognised by Suzuki and Kuriyama (2014). It should be noted that the 4.9 cycle corresponds to the cyclic signal visible in both 4-monthly and 12-monthly moving averaged and space integrated source function (red line in Figure 6).…”

Analyze the Coastal Storm Impulse (Cosi) Parameter and Beach Erosion at Hasaki Coast, Japan

“…As reported by Suzuki and Kuriyama 9) , the crossshore beach profile at HORS has a seasonal variation owing to the typhoons and low pressures in the fallwinter months (September to March : shoreline moves seaward) followed by relatively calmer conditions in the spring to summer (April to August : shoreline moves landward). Despite these morphological changes along the cross-shore, the alongshore profiles are nearly uniform 10) .…”

Dynamical Downscaling of Coastal Dynamics for Two Extreme Storm Surge Events in Japan

“…More recently, Troselj et al (2018) and Troselj et al (2019) conducted dynamical downscaling of coastal dynamics emphasizing freshwater impact from three major rivers and seasonal variabilities of SST and SSS, respectively. Furthermore, several past studies focused on shoreline variabilities along the Ibaraki Coast Galal, 2007, 2015;Suzuki and Kuriyama, 2014;An, 2016;Banno et al, 2016;Takewaka and Wen, 2017), with some of them dealing with impacts due to the October 2006 storms. Galal and Takewaka (2011) conducted erosion analyzes along the Kashima Coast in Ibaraki for the extreme October 2006 storm from the viewpoint of wave energy flux distribution.…”