Measurement and Prediction of Deformation of Conveyer Belts Carrying Gravel and Fine Sand Off Shimizu Coast

Sorting and Selective Movement of Sediment on Coast With Steep Slope- Masurements and Prediction

“…In the calculation, the applicability of the model is confirmed by the calculation to reproduce the measured bathymetric changes between 1998 and 2006, and the effect of elongating the existing breakwaters during the 10 years after their construction was compared. In the reproduction, the bathymetry in 1998 before the erosion was transformed into a model coast with straight parallel contours and a slope of 1/8 by expanding the coordinate system (Nishitani et al, 2008). From the assumption that this initial topography was in a dynamic equilibrium under the condition of a supply of 7.5×10 4 m 3 /yr of sand supply from the upcoast boundary (Nishitani et al, 2008), we assumed that this longshore sand supply in 1998 is reduced to 0.7×10 4 m 3 /yr after 1998 owing to the extension of the Lgroin, as shown in Fig.…”

“…Beach erosion has been severe on the Shimizu coast, which extends along the outer marginal coastline of the Mihono-Matsubara sand spit in Suruga Bay, as shown in Fig. 1, because of the decrease in longshore sand supply from the Abe River (Nishitani et al, 2008). As a measure against beach erosion, five sets of artificial headlands and an L-shaped groin (L-groin) were constructed between 1989 and 1999.…”

“…Analysis based on bathymetric surveys of this coast and bottom-sampling data suggests that there are two "conveyer belts" carrying gravel and fine sand along the coastline and that these conveyer belts have been disrupted by the construction of the coastal structures. Nishitani et al (2008) analyzed the mechanism of the development and deformation of these conveyer belts through a field investigation and a numerical simulation using the contour-line-change model (Serizawa et al, 2003). Although these conveyer belts continue to develop downcoast of the L-groin, they split into two, inducing longshore and offshore transport, because the seabed topography markedly changes and submarine canyons with a steep offshore slope have developed immediately north of the L-groin.…”

Model for Predicting Topographic Changes on Coast Composed of Sand of Mixed Grain Size and Its Applications

“…The analysis of the data sets suggests that there are two "conveyer belts" carrying gravel and fine sand along the coastline, and that these conveyer belts have been deformed as a result of the construction of the coastal structures. Here, the mechanism of the development and deformation of these conveyer belts is investigated using the present model (Nishitani et al, 2008). Figure Figure 21 shows the shoreline changes relative to the shoreline position in 1989 immediately before the construction of the artificial headlands.…”

“…Although the experimental and predicted results were in good agreement in this application, the applicability of the model to the coasts was still inadequate. Therefore, the model was applied to the following two model cases: beach changes associated with the beach nourishment using fine and coarse materials on the Chigasaki coast in Kanagawa Prefecture, Japan (Yoshioka et al, 2008), and the formation of a 'conveyer belt' composed of gravel and fine sand observed on the Shimizu coast (Nishitani et al, 2008). In this paper, these applications of the model are summarized and the effectiveness of the model is shown.…”