3D seismic data were used to infer how bottom currents control unidirectional channel migration. Bottom currents flowing towards the steep bank would deflect the upper part of sediment gravity flows at orientation of 1° to 11° to the steep bank, yielding a helical flow circulation consisting of a faster near-surface flow towards the steep bank and a slower basal return flow towards the gentle bank. This helical flow model is evidenced by occurrence of bigger, muddier (suggested by low-amplitude seismic reflections) lateral accretion deposits and gentle channel walls with downlap terminations on the gentle bank and by smaller, sandier (indicated by high-amplitude seismic reflectors) channel fills and steep channel walls with truncation terminations on the steep bank. This helical flow circulation promotes asymmetric depositional patterns with dipping accretion sets restricted to the gentle bank, which restricts the development of sinuosity and yields unidirectional channel migration. Our results aid in obtaining a complete picture of flow processes and sedimentation in submarine channels.