Digitizing a river

[azuikechukwuma]

At what scale will it be appropriate to show a river as a polygon.

[MarkEllis]

It depends on how wide the river is and the purpose of showing it as a polygon.  Some maps might be well served with generalized lines, others need the detail of a polygon.

[RyanFanani]

At what scale will it be appropriate to show a river as a polygon.

Depending on output scaling what you want.

Beside that, thats depend on what scale of your data input  🙂