Peakall, Jeffrey¹, William D. McCaffrey¹ 
(1) University of Leeds, Leeds, United Kingdom

ABSTRACT: Experimental Insights into Overbank Processes in Submarine Channels

Key differences between flow in subaerial and submarine channels are 1) the absence of a free upper surface 2) a reduced density difference between flow and ambient fluid and 3) the common occurrence of overbank flow in the submarine case. Here, we focus on the effects of the in-channel flow upon the component of flow that is super-elevated above the level of the levee crests and vice versa. The loss of a component of the super-elevated flow overbank impacts flow behavior and sedimentation both within and external to the channel. Here we report the first detailed experiments on this critical process. 
A series of experiments were run in a 1 m² tank with an inlet channel centered on one face. Small "levees" (inner and outer radii, 0.98 m and 1.17 m, respectively), of variable height were fixed to the tank floor abutting the inlet channel. Suspensions of mixed grain-size sediment (glass ballotini and silica flour) were mixed in a 4.5 liter lock box and rapidly released. Ultrasonic velocity profiling and siphon sampling were used to measure flow velocities and sediment concentrations respectively. Post-flow sediment distributions were accurately mapped. Flows were observed to follow the curved channel with very little overspill, even in cases where the mean flow height was more than twice that of the levees. The degree of overspill is quantified as a function of sediment stratification. Comparison is made between these submarine channel deposit geometries and those from fluvial systems.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.