Geomorphic variability of submarine channelized systems along continental margins: Comparison with fluvial meandering channels

Abstract

Understanding submarine sediment conduits is a challenging yet rewarding task given its applications in offshore industries and source-to-sink studies. Despite flow structure dissimilarities, sinuous submarine sediment conduits display morphologies similar to alluvial meandering rivers. An extensive quantification of degrees of (dis)similarity is however lacking. This study combines (i) a new geomorphic classification of submarine sediment conduits relying on cross-sectional data only, complemented by (ii) measurements of planform (sinuosity, wavelength, amplitude) and cross-sectional (bankfull width, depth, section area) parameters to compare alluvial meandering and submarine systems. We apply the methods to a worldwide dataset including 254 measurements from 35 modern systems. We identify four types of submarine sediment conduits including composite (i.e., canyon and valley) and unit (i.e., incised or leveed channel) types. The following findings arise. (i) Submarine sediment conduit geomorphology is strongly controlled by slope, mostly depending on location along the continental margin. Composite and erosive submarine sediment conduits are located on the continental slope and unit and constructive channels extend down to the basin floor. (ii) Submarine unit leveed channels form a consistent group of constructive, higher-order, smaller-size and more laterally mobile submarine sediment conduits. (iii) Submarine unit leveed channels are the most analogous to alluvial meandering rivers. (iv) Without discharge contribution from tributaries, the width and the area of long-running submarine sediment conduits increase as they migrate towards the abyssal plains. Such behavior is similar to rivers, although it is better explained for submarine sediment conduits by progressive flow deconfinement, and decreasing bank cohesion and friction angle.