CAA01/S484 (3) - (4)
Dredging is the deepening or widening of a channel for the passage of ships, whether in tidal waters or in an inland waterway. Dredging does not include normal maintenance work on an existing channel.
In more detail dredging is the removal of anything forming part of or projecting from the bed of the sea or of any inland water. It does not matter how the removal is done or whether at the time what is removed is wholly or partly above water. It also includes the widening of an inland waterway.
Dredging must be done in the interests of navigation.