Parameters - critical Shields parameter

The critical value of the Shields parameter, q_c, is used to indicate the thresh­old value of the dimensionless bed shear stress for initiation of motion. No transport will take place for values of the dimensionless bed shear stress q less than or equal to q_c.

Values of q_c between 0.040 and 0.060 may be specified.

Note that the user-specified value is not used in the Engelund & Hansen, the Ackers & White and the Zyserman & Fredsøe transport theories. The first two methods do not include a threshold value for the initiation of motion, and in the third method q_c is internally set to 0.045.