All the factors mentioned here i.e the volume of water, the speed and shape of the stream do effect the eroding capability of a stream. It also determines the path of the rest of the river.
Explanation:
In the mountainous region, where the river originates, the landforms are very steep. This results in more gravity force which leads to the high speed of the stream. This makes more vertical erosion than horizontal erosion. This also leads to less meandering of the river path. The river is very deep and straight in this phase.
As the river comes down to plains and estuaries, the landforms are less steep or more or less flat. So the speed of the flow of river gets greatly reduced and this leads to horizontal erosion than vertical erosion. Various landforms like meandering river, ox bow lakes are seen there. The river is slow and not very deep.
Again, bigger streams with more water erode more than smaller streams because of the weight of water falling on the soil.
