title: Backwash process of marine macroplastics from a beach by nearshore currents around a submerged breakwater.
abstract: A key factor for determining the residence time of macroplastics on a beach is the process by which the plastics are backwashed offshore (backwash process). Here, we deduced the backwash process of plastic fishing floats on Wadahama Beach based on the analysis of two-year mark-recapture experiments as well as nearshore current structures revealed by sequential images taken by za webcam installed at the edge of a cliff behind the beach. The analysis results revealed the occurrence of a combination of offshore currents and convergence of alongshore currents in the surf zone in storm events around a submerged breakwater off the northern part of the beach, where 48% of the backwashed floats were last found. We conclude that the majority of the floats on the beach were transported alongshore and tended to concentrate in the convergence zone, from where they were backwashed offshore by the nearshore currents generated in the events.
authors.affiliation: Coastal Zone Systems Division, Coastal, Marine and Disaster Prevention Department, National Institute for Land and Infrastructure Management, 3-1-1 Nagase, Yokosuka, Kanagawa 239-0826, Japan.
authors.forename: Tomoya
authors.initials: T
authors.lastname: Kataoka
authors.affiliation: Department of Civil and Environmental Engineering, Faculty of Engineering, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan. Electronic address: hinata@cee.ehime-u.ac.jp.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Hinata
authors.affiliation: Department of Architecture and Civil Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi, Aichi 441-8580, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Kato
mesh_terms: D004784:Environmental Monitoring / Q000379:methods; D007564:Japan; D010969:Plastics / Q000032:analysis*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D010969:Plastics; D014874:Water Pollutants, Chemical
keywords: Marine macroplastics; Mark-recapture experiment; Nearshore current; Residence time; Submerged breakwater