Takashi Sakamaki, Tohoku University, Department of Civil & Environmental Engineering, and Advanced Institute for Marine Ecosystem Change (WPI-AIMEC), Sendai, Japan, Yuji Hatakeyama, Port and Airport Research Institute, Yokosuka, Japan, Hikaru Saito, Tohoku University, Department of Civil & Environmental Engineering, Sendai, Japan and Megumu Fujibayashi, Kyushu University, Faculty of Engineering, Fukuoka, Japan