The critical value of the dimensionless bed shear stress (the Shields parameter), qc, is used to indicate the threshold value for initiation of sediment motion. MIKE 21 ST expects and will accept values of qc between 0.040 and 0.060.
The user-selected value for qc will not be used if you select either the Engelund & Hansen Transport Theory or the Zyserman & Fredsøe Transport Formulation. No threshold for initiation of motion is used in the first case, while qc is assigned a value = 0.045 in the second.