The character of a gradually varied flow is classified in terms of actual channel slope compared to that of slope required for producing uniform flow . They may be,

• Mild slope with (i.e. the flow would be sub-critical , if it were of uniform depth)
• Steep slope with (the flow would be super-critical , if it were of uniform depth)
• Horizontal slope with
• Adverse slope, (i.e. flow uphill)

Thus, it may be inferred from the above that the determination of whether the flow is sub-critical or super-critical depends solely on whether or respectively. For gradually varying flows, the conditions for sub-critical and super-critical flows are met by and depth of flow. For example, with , it is possible to have either or depending upon the depth of flow i.e. or respectively.