Formative conditions and sedimentary structures of sandy 3D antidunes : an application of the gravel step-pool model to fine-grained sand in an experimental flume
Antidune ; Experimentation ; Fluvial processes ; Hokkaido ; Japan ; Model ; Palaeohydrology ; Sedimentary structure
The AA. estimated formative conditions of gravel step-pool morphologies and applied them to the formation of 3D antidunes over a sand bed. Formative conditions are expressed in terms of a relationship between the water discharge per unit width
and the bed slope. Flume experiments demonstrated that 3D mound-like antidune configurations and their associated internal sedimentary structures could be preserved. Internal sedimentary structures were characterized by shallow lens-like structures whose bases
were erosional. Although gently-dipping concave-upward lamination was dominant, convex-upward lamination was occasionally observed. The dimensions of lenticular lamina-sets can be used to estimate antidune geometry. Thus if 3D antidunes can
with regard to its dependence on flume width. These results suggest that the bed roughness geometry develops towards a condition that provides the maximum bed stability for a given grain size distribution. In contrast to a variety of other studies, antidunes
did not contribute to the generation of the step structures. However, the data of the presented study fits well into the region of antidune formation proposed by Kennedy for sand-bed rivers. The considerations of the Kennedy region of antidune
Antidune ; Colorado ; Cours d'eau ; Dynamique fluviale ; Ecoulement ; Etats-Unis ; Géographie physique ; Hydrodynamique ; Lit fluvial ; Medano Creek ; Mécanique des fluides ; Rugosité
Les courants de fonds sableux sont à l'origine d'un écoulement non permanent particulièrement instable. Les coupures qui se propagent vers l'aval sont formées par des antidunes instables qui retiennent l'eau en gagnant en amplitude puis la relâchent
The main aim of this study was to monitor the temporal evolution of step-pool morphology and, at the same time, the influence of steepness on the total bedload volume yielded by comparable flood hydrographs. The analogy of step spacing with antidune