Abstract

When a turbidity current flow decreases in velocity due to a decrease in bottom slope, the thickness of the flow must correspondingly increase to maintain continuity of discharge. This increase has been offered as a possible explanation for observed systematic increases in the relief of submarine channels along their lengths.

A simplified computer model of turbidity current flow along a channel is developed which indicates that without any dilution of the flow by water entrainment, a reasonable decrease in channel-axis slope could more than double the thickness of the flow. With dilution, the thickness could easily increase by a factor four or more. The systematic increases in channel relief might therefore be explained.

The approach is applied to Cascadia Channel, located off the coast of the northwest United States, to test whether reasonable amounts of flow dilution could account for the observed increase in channel relief. It is found that continuity of flow could explain much of the increase, but subsequent channel erosion (deepening and widening) has to be called upon to account for the entire increase in channel cross-sectional area.

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