It is the process by which large rocks are removed from a waterway. This process changes a waterway's substrate composition as well as its shape. Dredging can turn a shallow, winding stream with many sizes of rocks on its bottom into a deep, straight stream with only small rocks on its bottom. More recently, streams have been dredged as a means of flood protection.
Some landowners even dredge streams to create more convenient or prettier channels.
Removal of large rocks from a stream can decreases the stream's resistance to flow. This results in an increase in the stream's velocity . Increased velocity can cause downstream flooding. In addition, the removal of large rocks often leaves a stream bed with small, uniform-size rocks. This destroys important habitats of aquatic plants, fish, amphibians, and aquatic insects .