The present paper concerns the computation of regime channel characteristics in cohesionless alluvium. The computational method proposed rests on the channel formation criterion derived from the thermodynamic principles, and on the expression of the aspect ratio determined in the earlier works of the authors on the basis of zero cross-transport rate at the regime stage. The thermodynamic considerations are based on the first and second laws, and the Gibbs' TdS equation: the alluvial stream is treated as an isolated, uniform system. The regime channel formation process is determined by the flow rate and the physical nature of the materials involved (alluvium and water): the sediment transport rate is viewed as an outcome of the phenomenon rather than as one of its characteristic parameters. The regime channel characteristics computed from the suggested method are compared with field and laboratory data of various sources.