The passages are stopped - The ferries are seized, occupied. The historians state that when Cyrus captured the city his troops moved down the bed of the river and occupied all these ferries, finding at each of them the gates negligently left open. See the Daniel 5:1 note.
The reeds - literally, the marshes or pools, which formed an important part of the defenses of Babylon, were dried up as completely as a piece of wood would be consumed by fire.