2024 Volume 80 Issue 17 Article ID: 24-17145
The porosity in the surf zone’s sand layer is known to exhibit variations. However, there are few studies on this, and existing models of sediment transport and topography change do not take into account the spatio-temporal variation of porosity in the sand layer. In this study, experiments were conducted using a tabletop wave generator. Regular waves were generated on the constructed sand slope, and images of the sand layer were taken by an X-ray CT system to measure the spatio-temporal variation of porosity under conditions where the topography was going through constant changes. The recorded images were analyzed to investigate the relationship between the topographic change and the porosity change in the sand layer. As a result, it was confirmed that there were layers with large porosity at the surface during topographic change in both accretion and erosion areas. The thickness of the layers (i.e. with large porosity) were about 4 mm in the accretion area and about 2 mm in the erosion area. The differences in thickness were due to loose sediment deposition and surface scraping in the accretion area and erosion area, respectively, leading to a twofold increase in the former.
