Bankfull hydraulic geometry of submarine channels created by turbidity currents: Relations between bankfull channel characteristics and formative flow discharge

Detailed bathymetric surveys of the seafloor have enabled the identification and analysis of submarine channels worldwide. Previous authors have remarked on the morphologic similarity of submarine channels and rivers, and have identified a number of similarities and differences in processes of flow and sedimentation. In this study, we compare the width, depth, and slope of 177 submarine channel cross‐sections to that of 231 river cross‐sections. The results indicate that submarine channels have cross‐sectional dimensions that can exceed the dimensions of the largest rivers on earth by an order of magnitude. For rivers and submarine channels with similar width or depth, the slope of submarine channels can be up to two orders of magnitude greater than the slope of rivers. An analysis of trends in driving force vs. channel size suggests that a reasonable estimate of the volumetric sediment concentration of channelized turbidity currents lies in the range C = 0.2% to 0.6%. Bankfull turbidity current velocities are estimated using this range in concentration. Friction coefficients are based on values identified for large rivers and a modified Chezy equation. These velocities are then used in a classic hydraulic geometry analysis of the submarine channels, which shows that submarine channels and rivers follow similar power law trends in width, depth, and velocity as functions of bankfull discharge.