text: the faster the streams velocity is, the quicker the erosion takes place.  this is caused by increased friction as velocity increases.\n\nit's sort of like falling from a plane.  you go faster and faster, and as your velocity increases, so does the friction.  soon, you'll hit terminal velocity, or the point where you are no longer accelerating.  the force of friction with the air eventually will equal out with the force of you falling, but still, as you get going faster there is more friction.\n\nthis friction causes the erosion and so the faster the velocity the more the rocks, soil, etc. erodes.