Slope Control on Submarine Channel Widths

Abstract

Abstract Submarine channel systems associated with turbidity currents show characteristic variations in channel width and channel slope with distance from source. The most proximal parts are generally formed from pre-existing canyons but these are followed by channels which show segments with two distinct behaviors: (1) sections where channel width is approximately constant (70% of total length) despite significant changes in slope; (2) sections where rapid changes in channel width are associated with relatively small changes in channel slope (30% of total length). Here, I show that width versus slope relationships are controlled by the Froude number of flows along a channel. For low Froude numbers, channel widths should be approximately constant whilst rapid-width-change segments of submarine channels are accurately reproduced if it is assumed that these segments support near-critical flows. Theoretical analysis of momentum conservation in one-dimensional (i.e., channelized) flows supports this concept of two distinct flow regimes: one in which Froude numbers are low and channel widths are constant and one in which Froude numbers oscillate around unity and channel widths fall rapidly with channel-floor slope.