This paper describes a semi-analytical model of spatially-developing turbidity flows, and concentrates on two particular aspects: (i) the possible conditions for ignitive autosuspension in a particular submarine channel (the Kaikoura Canyon–Hikurangi Channel System, east of New Zealand); and (ii) the relationship between the internal Richardson number of the flow, and the possibility of ignitive autosuspension.

The results confirm that autosuspension is promoted by a steep channel gradient, a large flow thickness, and fine grain size. The model, as applied to the Kaikoura Canyon–Hikurangi Channel system in New Zealand, indicates that ignition is possible in the Kaikoura Canyon and the proximal reaches of the Hikurangi Channel.

From analysis of the turbulent-energy balance within the flow, it emerges that ignition is impossible in subcritical flows (Ri > 1). Our work implies that turbidity currents that are depositing significant volumes of sediment are subcritical rather than supercritical. This may have significant implications for architectural development in natural systems.

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