Braiding of submarine channels controlled by aspect ratio similar to rivers

• Published in: Nature geoscience Vol. 8; no. 9; pp. 700 - 703
• Main Authors: Foreman, Brady Z., Lai, Steven Y. J., Komatsu, Yuhei, Paola, Chris
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.09.2015; Nature Publishing Group
• Subjects: 704/2151/215; 704/2151/3930; Density currents; Earth Sciences; Earth System Sciences; Geochemistry; Geology; Geophysics/Geodesy; letter; Ocean floor; Rivers; Sediment concentration; Submarine canyons; Suspended sediments; Turbidity; Water depth
• ISSN: 1752-0894; 1752-0908
• DOI: 10.1038/ngeo2505

Braided channels are rare in submarine environments, yet common in fluvial systems. Laboratory experiments suggest that the formation mechanisms are the same, but submarine channels are typically not wide enough to promote braiding. The great majority of submarine channels formed by turbidity and density currents are meandering in planform; they consist of a single, sinuous channel that transports a turbid, dense flow of sediment from submarine canyons to ocean floor environments 1 , 2 . Braided turbidite systems consisting of multiple, interconnected channel threads are conspicuously rare 1 . Furthermore, such systems may not represent the spontaneous planform instability of true braiding, but instead result from erosive processes or bathymetric variability 3 , 4 , 5 . In marked contrast to submarine environments, both meandering and braided planforms are common in fluvial systems 6 , 7 . Here we present experiments of subaqueous channel formation conducted at two laboratory facilities. We find that density currents readily produce a braided planform for flow aspect ratios of depth to width that are similar to those that produce river braiding. Moreover, we find that stability model theory for river planform morphology 8 successfully describes submarine channels in both experiments and the field. On the basis of these observations, we propose that the rarity of braided submarine channels is explained by the generally greater flow depths in submarine systems, which necessitate commensurately greater widths to achieve the required aspect ratio, along with feedbacks 9 , 10 among flow thickness, suspended sediment concentration and channel relief that induce greater levee deposition rates and limit channel widening.