River Gradient | Channel Roughness | Channel Shape |

The shape of the channel or its cross section affects the wetted perimeter. The wetted perimeter refers to the extent to which water is in contact with its channel. The greaterthe wetted perimeter, the greater the friction between the water and the banks and the bed of the channel, and the slower the flow of river.

Wetted perimeter is calculating by adding the length and the breadth of the channel in
contact with water.