Simulating depth‐averaged, one‐dimensional turbidity current dynamics using natural topographies

Abstract

AbstractThis study simulates turbidity currents through natural submarine topographies using a steady, one‐dimensional, depth‐averaged model to determine if modeled flows might traverse the length of channel forms observed at the seafloor or in shallow seismic data sets. To accomplish this, we calculated flow dynamics based on 50,000 sets of initial conditions drawn randomly between prescribed bounds and identified those conditions that allowed flows to traverse the naturally observed systems. We also used flow height and velocity to rule out initial conditions that produced flows that would be broadly accepted as unrealistic. We found that a small percentage (2.3–9.7%) of flows traversed the measured portion of these natural systems and maintained plausible peak depth‐averaged velocities when laboratory‐derived clear‐water entrainment rules were used. However, even these flows reached peak heights that were many times (10–200) greater than that of the channel bottom to levee crest relief. When clear‐water entrainment was removed from the model, a larger percentage of flows (34.5–41.6%) traversed the measured channel geometries, maintained lower ranges of flow height, and typically had higher flow velocities. Alternate entrainment relationships allowed flows to maintain realistic flow heights and velocities. We speculate that the unrealistic flows produced using clear‐water entrainment rules arise because flow loss through stripping and/or overbank collapse is neglected in this one‐dimensional model, or extrapolating laboratory‐measured clear‐water entrainment rules to the field is problematic.