Its mouth is divided by sandbanks into many channels.
Above Agram the Save is used chiefly for floating rafts of timber; east of Sissek it is navigable by small steamboats, but, despite its great volume, the multitude of its perpetually shifting sandbanks interferes greatly with traffic. Steamers also ply on the Una, the Drave below Barcs, and the Danube.
As the mouth is choked with sandbanks, goods are disembarked at Mariinsk and carried by train (9 m.) to Alexandrovsk at the head of the Gulf of Tartary.
In front of the delta are sandbanks and rocks which prevent the passage of vessels except by a canal, 18 m.
One consequence of this is that the bed of the river just below Hamburg is obstructed by a bar, and still lower down is choked with sandbanks, so that navigation is confined to a relatively narrow channel down the middle of the stream.