Answer:
The flow
Step-by-step explanation:
If you want to determine whether the direction of the river you need to figure out where the river is going how do you do that?
You can figure out the flow of the river by looking at it at seeing how it flows. To make it even more easier is by looking at a waterfall ( I think you would know the direction. ) It is much easier to look at the flow on how it is going it is very easy to do..