Model for Predicting Beach Changes on Coast with Sand of Mixed Grain Size Based on Bagnold's Concept

Mechanism of Offshore Sand Discharge Into Submarine Canyon Triggered by Constructing Detached Breakwater Close to Shoreline

“…This installation of the oblique detached breakwater is considered to have caused the offshore discharge of sand through the submarine canyon because of the obstruction of southward longshore sand transport. This phenomenon was reproduced using the BG model proposed by Serizawa et al (2007). …”

“…(1) (Serizawa et al, 2007). Consider Cartesian coordinates (x, y) and that the elevation at a point Z (x, y, t) is a variable to be solved.…”

“…Calculation for four cases were carried out: the present bathymetry was reproduced in case 1, the detached breakwaters were installed in case 2,detached breakwaters with an increased wave transmission coefficient were installed in case 3 and detached breakwater No. 1 next to Calculation method BG model considering grain size change (Serizawa et al, 2007) Angular spreading method for irregular waves (Sakai et al, 2006) Initial …”

“…Uda et al (1989), Uda (1997) and Kanazawa et al (2006) studied the field conditions around these submarine canyons through field observations, but the exact cause of sand loss into the submarine canyons has not yet been clarified, and therefore it is difficult to take concrete measures against beach erosion. In this study, shoreline changes using past aerial photographs and measurement by a narrow multibeam survey were carried out, and the mechanism of sand loss into the submarine canyon was numerically investigated using the BG model (Serizawa et al, 2007). 1 National Institute for Land and Infrastructure Management, 1 Asahi, Tsukuba, Ibaraki 305-0804, Japan 2 Public Works Research Center, 1-6-4 Taito, Taito, Tokyo 110-0016, Japan 3 Coastal Engineering Laboratory Co., Ltd., 1-22-301 Wakaba, Shinjuku, Tokyo 160-0011, Japan Figure 2 shows the bathymetry between the Kurobe River mouth and the Aramata region measured in 2005 by a narrow multibeam survey and the alignment of transects.…”

“…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). …”