What would happen over time if harbours and rivers weren't dredged?

Question

Explain

Answer 1

Silt would build up over time and the depth of the area would be reduced, thus making it difficult if not impossible for large ships to safely travel in said area.

Answer 2

Well the harbors and rivers have to be dredged so the dept of the water will be deep enough for ships to moves

Answer 3

they would fill up with silt and ocean going ships would not be able to load and unload cargo and the center of commerce would move down stream.