[H-CG28] Earth surface processes related to deposition, erosion and sediment transport

[HCG28-P08] Linear stability analysis of plane beds with active suspended load

Koji Ohata¹, *Hajime Naruse¹, Norihiro Izumi² (1.Department of Geology and Mineralogy, Graduate School of Science, Kyoto University, 2.Graduate School of Engineering)

Keywords:bedform, turbidite, plane bed, dune, stability analysis

Plane beds develop under riverine and marine environments and can be recorded as
parallel lamination in sandstone beds, such as those found in turbidites. However,
whereas turbidites typically exhibit parallel lamination, they rarely feature dunescale
cross lamination. Although the reason for the scarcity of dune-scale crosslamination
in turbidites is still debated, the formation of dunes may be dampened
by suspended load. Here, I perform linear stability analysis to show that flows
with suspended load facilitate the formation of plane beds. For a fine-grained bed,
suspended load can promote the formation of plane beds anddampen the formation
of dunes. These results of theoretical analysiswere verified with observational data
of plane beds under open-channel flows. In the case of coarse-grained beds, the
stability diagrams do not coincide with the experimental data of plane beds under
sheet flows. Further analytical studies of bedforms should consider sheet flows,
one of the transport modes associated with open-channel flows and sediment-laden
gravity currents.