River sources tend to be at the top of mountains or areas of high elevation. This means that rivers impact the entire terrain from mountains to seas and oceans.
I hope this Helps!
Becky's speed is her distance travelled which is 30 km divided by her time travelled of 2.5 hours which gives her average speed of 12 km/hour which is a quite good speed if she was say riding a bicycle and which would give her a good aerobic workout.
