Answer:
Streams need vitality to move material, and levels of vitality change as the waterway moves from source to mouth.
At the point when vitality levels are high, huge rocks and stones can be moved. Vitality levels are generally higher close to a waterway's source, when its course is steep and its valley slender. Vitality levels rise considerably higher in the midst of flood.
At the point when vitality levels are low, just little particles can be moved (assuming any). Vitality levels are most reduced when speed drops as a waterway enters a lake or ocean (at the mouth).