MECHANISM OF OFFSHORE SAND DISCHARGE INTO SUBMARINE CANYON TRIGGERED BY CONSTRUCTING DETACHED BREAKWATER CLOSE TO SHORELINE

Koji Yamada, Takaaki Uda, Yoshio Suwa, Toshiro San-nami, Kou Furuike, Toshinori Ishikawa

Abstract


Several submarine canyons have developed offshore of the Aramata region of the Shimoni-ikawa coast in Toyama
Bay, which is one of the three deep bays in Japan. The Kurobe River with a steep bed slope flows into the sea
immediately north of this region, and a large amount of sediment has been supplied to this area, which has been
transported by southward longshore sand transport. However, beach erosion has occurred owing to the decrease in sediment supply from the Kurobe River. Furthermore, since the construction of detached breakwaters as a measure
against beach erosion, offshore sand transport has accelerated and beach erosion has become more severe. In this
study, aerial photographs and bathymetric survey data were analyzed, then the mechanism of offshore sand transport
was investigated using the BG model proposed by Serizawa et al. (2007).

Keywords


submarine canyon; offshore sand transport; detached breakwater; Shimoni-ikawa coast

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