| Three main topics constitute this thesis: (a) debris flows, (b) depositional turbidity currents in intraslope minibasins, and (c) ponded turbidity currents in reservoirs.; Debris flows. Experiments in subaqueous and subaerial laboratory settings were performed to evaluate the ability of an unconfined debris flow to remobilize or rework an antecedent deposit. In the subaerial case reworking was immediate and extensive. By the contrast, in the subaqueous case reworking of the deposit of the first run by the second run was suppressed. Part of the reason for this appears to be hydroplaning of the debris flow heads. As the deposit built up, however, considerable reworking was eventually observed in the subaqueous case as well.; Depositional turbidity currents in intraslope minibasins. A theory is developed to describe sediment deposition in minibasins. Two key aspects of the “fill and spill” process are revealed: (a) the formation of an internal hydraulic jump as a turbidity current flows into a confined basin, and (b) the detrainment of water across a settling interface at the top of the ponded turbidity current downstream of the hydraulic jump. It is shown that sufficiently strong detrainment can consume the flow, so that there is no outflow of either water or sediment even with continuous inflow. As the basin fills with sediment, however, overspill is eventually realized. Upon this theory a numerical model is tested and verified against two experiments. A sample calculation provides an example of applying the model at field scale.; Ponded turbidity currents in reservoirs. A moving-boundary formulation of reservoir sedimentation is presented, also capturing the dynamics of turbidity currents. The formulation considers sediment of two sizes, sand and mud, each characterized in terms of a single grain size. The sand deposits fluvially to form a delta topset, and by avalanching form a delta foreset. The remaining muddy water plunges at a point above the foreset forming a bottomset deposit. This formulation is applied at experimental and field scale, and compared against the results of an experiment. The results represent a mechanistic quantification of the sediment trap efficiency of reservoirs. |
