Question

How does deepening of river bed help in preventing erosion of soil?

Answer 1

Probably because the deepening of the water bed results in the slowing down of water flow as as water gets more area to flow, thus the water moving with slow speed is not able to cause much soil erosion or prevents it .

Answer 2

Plants break the effect of a raindrop before it hits the dirt, lessening the dirt's capacity to disintegrate.

Plants in wetlands and on the banks of streams are vital as they moderate down the stream of the water and their underlying foundations tie the dirt, anticipating erosion.

Probably in light of the fact that the extending of the water bed results in the backing off of water stream as water gets more region to stream, in this way the water moving with moderate speed can't cause much soil disintegration or counteracts it