Within the receiving basin, wave and current energy is extremely low. This water-level fluctuation has led to three zones in the delta proper. It is believed that these ridges and swales represent coastal banks now stranded by the falling level of Caspian Sea. The third zone is the submarine part of the delta, which forms a broad platform extending 30 to 60 km offshore. Flow in the channels is so erratic that, for much of the year, little or no water flows in the channels.
Strong winds erode the channel floors and form linear dunes on the overbank areas.
The active channels that contain river flow are ice bound during the period December through March. Before the construction of dams, these complex channels constantly shifted their position with each flood. Many of these show little or no orientation and are generally devoid of substantial vegetative cover. A similar extensive system bounds the western flank of the delta, in which interdune areas enclose elongate lakes. This figure shows the complex distributary channel patterns of the river mouth and the adjacent mudflats.