The stable channel geometry has attracted the attention of hydraulic engineers for quite a long time. Various criteria have been proposed to explain the self-formed geometry of a channel. Based on the optimal cost-structure of flow systems, and using geometric programming, the present investigation formulates an objective function to yield Lacey’s stable channel dimensions. The function may be useful to reveal many details of the stable channel geometry. The stable channel geometry has attracted the attention of hydraulic engineers for quite a long time. Various criteria have been proposed to explain the self-formed geometry of a channel. Based on the optimal cost-structure of flow systems, and using geometric programming, the present investigation formulates an objective function to yield Lacey’s stable channel dimensions. The function may be useful to reveal many details of the stable channel geometry.