HYDRAULIC AND MORPHODYNAMIC BEHAVIOR OF TURBIDITY CURRENT CONFLUENCE

The hydraulic and morphodynamic behavior of turbidity currents traveling through submarine channels has received increased attention from the scientific community in the past several decades. Although much progress has been made in understanding turbidity current behavior, many properties of these currents remain a mystery. Submarine channel confluences are common features of continental margins; such joining channels are found in the Espirito Santo Basin of SE Brazil, the Cascadia Margin of NW United States, and in the South China Sea near Brunei Darussalam of NW Borneo, to name a few. The present work aims to study the hydraulic and morphodynamic consequences of two turbidity currents colliding. Along with a general study of turbidity current confluence by measuring current height, velocity, and density after the collision, hydraulic and morphodynamic interest in such confluences will focus on making comparisons to or contrasts with subareal rivers. Such comparisons include characterizing the flow separation zone downstream of the junction and measuring circulation patterns at the junction. The experiments are conducted by first releasing a dilute saline solution into each upstream reach of a fixed-bed T-shaped flume initially filled with fresh water. Several runs are made at various junction angles, and measurements of current height, velocity, and density are taken upstream and downstream of the junction, along with three dimensional velocity profiles measured in the mixing zone. The present study is also accompanied by an analytical solution predicting that when two equal density turbidity currents collide, the resulting current will have a higher velocity. Additional work is planned to incorporate the affects of circulation in the analytical solution and to expand the experimental investigation to include an erodible bed. This will be conducted in the same physical model with a sustained turbidity current in the primary channel and a pulse released in the side channel.