NEW INSIGHTS FROM EXPERIMENTAL DATA INTO THE CONCEPT OF EQUILIBRIUM IN COMPOSITE SUBMARINE CHANNEL-LEVEE SYSTEMS AND CHANNEL DEPOSIT CHARACTER
The relationship between the evolution of turbidity currents and sinuous channels is investigated through scaled experiments using a channel model with 15 bends. Physical modelling allows examination of velocity distribution, inner channel and overspill flow properties, alongside their associated deposits. Nominally identical particulate turbidity currents were created using a known initial mass concentration of silica flour. Current understanding of flow development predicts that the turbulence of the flow would decrease as the axial slope decreases. Preliminary data show an unexpected trend in the results: turbidity current turbulence decreases between 3 degree and 2 degree slope and increases between 2 degree and 1 degree slope, indicating a low at the mid slope angle. The initial findings question the present understanding of the development of an equilibrium flow state and turbulence propagation through a sinuous channel system.
Flow morphology evolves and adjusts to the channel form throughout the system. Velocity and overspill is greatest in the proximal bends forming coarse grained levee deposits. In the distal bends the deposit becomes progressively finer, until the final five bends, as flow velocity decreases and overspill is predominantly confined to the outer edge of the bend apex stripping the flow of the coarse grains. The intra-channel deposit grain size decreases down channel and remains finer grained than the levee deposits.
The flux in overspill seen along the model channel indicates that the rate at which the channel levees are built alters throughout the system. The overspill continues to occur through the system but decreases distally. This matches the observed decrease in channel width and height in natural channel systems.