Antidune

Antidunes are typically found in fluvial environments in shallow areas with a high flow rate.

Flume studies have shown that they can also occur in submarine environments beneath density flows like turbidity currents.

[1] Antidunes migrate upstream because the stream flow is shallow and fast in the trough and slows and deepens over the crest.

The inertia of the flow moves the shear stress maximum and minimum slightly downstream of the trough and crest.

The term antidune was coined by G.K. Gilbert in a 1914 US Geological Survey Professional Paper entitled “Transportation of debris by running water”.

He applied dimensional analysis to Gilberts' results and came up with transition points using Froude numbers versus velocity and hydraulic radius.

Surface waves forming in phase above antidunes in a small stream. Water flow is away from the camera.
Water flowing over bedforms in sand under unidirectional flow to the right. Numbers correspond broadly to increasing flow regime, i.e., increasing water flow velocity. For dunes, the water surface is low over the dune and high over the interdune. For antidunes, flow depth is roughly the same everywhere, which means the water surface is high over the antidune and low over the interdune.