The evolution of a turbidite- channel and levees related to the flow dynamics of high-density turbidity currents; Results from flume experiments.
Braack, M.C. ter
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The flow dynamics of turbidity currents in relation to the resulting channel/levee morphology is still poorly understood. In a series of 3D flume experiments the evolution of a turbidite system will be studied in relation with the flow dynamics of high-density turbidity currents. These experiments were carried out in the Eurotank laboratory at the Utrecht University. During the execution of the flume experiments the boundary parameters (concentration, sediment composition, discharge and slope gradient) were varied to explore which boundary settings are necessary to successfully simulate a turbidity system in the laboratory. Velocity profiles were obtained from the turbidity current during the experiment. Deposits were measured with a laser in order to study the morphology of channel and levees and to create digital elevation models of the deposits. The results of the flume experiments show some similarities with natural turbidite systems but also some fundamental differences are present between overall sediment composition, sediment input orientation and lobe deposits. In future experiments these should be incorporated in order to achieve more realistic results. The results of the velocity profiles and laser scans conclude that confinement of the current is the main factor causing decreasing velocities outside the channel. An increasing channel gradient is the main factor causing increasing velocities inside the channel. Channel formation was initiated by deposition which lead to channelization of the turbidity current and formation of a channel with accompanying levees. After channelization of the flow, velocities in the channel increase and incision in the channel increases. This leads to the transition from an depositional system towards an erosional/depositional system. The turbidite system created in this study started as a depositional system. This is in contradiction with suggestions of Maier et al. (2013) and others (e.g. Campion et al., 2000; Gardner & Borer, 2000; Schwarz & Arnott, 2007; McHarue et al., 2011) which state that such systems do not exist. Results of the backslope of one of the levees are in good agreement with previous flume experiments and natural turbidite systems.