A nonlinear model of flow in meandering submarine and subaerial channels

A generalized model of flow in meandering subaqueous and subaerial channels is developed. The conservation equations of mass and momentum are depth/la yer integrated, normalized, and represented as deviations from a straight b ase state. This allows the determination of integrable forms which can be s olved at both linear and nonlinear levels. The effects of various flow and geometric parameters on the flow dynamics are studied. Although the model i s not limited to any specific planform, this study focuses on sine-generate d curves. In analysing the flow patterns, the turbidity current of the suba queous case is simplified to a conservative density flow with water entrain ment from above neglected. The subaqueous model thus formally corresponds t o a subcritical or only mildly supercritical mud-rich turbidity current. By extension, however the analysis can be applied to a depositional or erosio nal current carrying sand that is changing only slowly in the streamwise di rection. By bringing the subaqueous and subaerial cases into a common form, flow behaviour in the two environments can be compared under similar geome tric and boundary conditions. A major difference between the two cases is t he degree of superelevation of channel flow around bends, which is modest i n the subaerial case but substantial in the subaqueous case. Another differ ence concerns Coriolis effects: some of the largest subaqueous meandering s ystems are so large that Coriolis effects can become important. The model i s applied to meander bends on the youngest channel in the mid-fan region of the Amazon Fan and a mildly sinuous bend of the North-West Atlantic Mid-Oc ean Channel. In the absence of specific data on the turbid flows that creat ed the channel, the model can be used to make inferences about the flow, an d in particular the range of values of flow velocity and sediment concentra tion that would allow the growth and downfan migration of meander bends.