Applications of 3D Laser and X-ray CT Scanners to Geo-Environmental Properties on Intertidal Mudflat

Abstract

Three-dimentionalLaser and X-ray Computed Tomography (CT) Scanners have been applied to investigate a time-space evolutions of wave-generated ripple geometry and vertical sediment structures of intertidal mudflat with non-destructive conditions at Shirakawa River mouth. Field observations were conducted in two places where there are many Ruditapes philippinarums (clam-dominant area) or not (calm non-dominant area). Time-space evolutions of wave-generated ripple geometry at non-dominant area were found to be larger than those of calm-dominant area. Reconstructing three-dimensional images using CT value, retention water in the intertidal sediment at calm-dominant area existed up to 6cm below the sediment surface during dry cycle of tide motions.

Burrowing ability as a key trait in the establishment of infaunal bivalve populations following competitive release on an extensive intertidal sandflat

“…Of these, the present study was conducted on the latter part (=3.39 km 2 ; hereafter, Shirakawa sandflat). During late autumn to early spring, the Shirakawa sandflat is subject to northwesterly wind-driven wave action and the resultant intense sediment erosion (Yamada and Kobayashi, 2004;Yamada et al, 2007). In the other seasons, the sandflat receives minimal waves due to the predominant southwesterly winds.…”

“…On the Shirakawa sandflat, the sediments of the high to mid-tide zone are unstable (Yamada et al, 2007), which would be unsuitable for juveniles of R. philippinarum to survive in (Breber, 2002;Ponurovskii, 2000Ponurovskii, , 2008Yamada et al, 2007). By contrast, the sediment of the low-tide zone is stable and contains more shell fragments (Yamada et al, 2010), which can be used by R. philippinarum juveniles as a base for their byssus thread attachment to prevent dispersal (de Montaudouin, 1997).…”

“…By contrast, the sediment of the low-tide zone is stable and contains more shell fragments (Yamada et al, 2010), which can be used by R. philippinarum juveniles as a base for their byssus thread attachment to prevent dispersal (de Montaudouin, 1997). Yamada et al (2007) used a three-dimensional laser scanner technique to detect a change between two consecutive dates in winter for wave-generated sediment ripples in the low-tide zone (R. philippinarum-dominant area) and the mid-tide zone (nondominant area) on the Shirakawa sandflat. They found that the former surface exhibited a flatter and lower relief and a smaller daily change.…”