Abstract

Changes in the Caspian rivers sediment yield and the Caspian Sea level fluctuations strongly influence on the river mouth processes, especially in large protruding deltas. Monitoring of the Caspian deltas was provided by space surveys for the Sulak, Kura, Terek, Ural river deltas. The analysis of created maps shows that the following changes during the period of the sea level rise are typical of protruding deltas of the Caspian Sea: flooding of low laying periphery parts; wave abrasion of deeper parts of the nearshore slope and formation of spits from material of abrasion; formation of bar-lagoon complex; hydrographic network reconstruction. Such changes are typical of the river mouths where the sediment discharges over the last period decreased due to reservoirs construction in the river basins. The changes of this type are especially well marked in the Sulak River and the Kura River deltas. Another tendency was observed in the “new” Terek River delta, which formation began in 1970-s, when an artificial channel through the Agrakhan Peninsula led out the river to the open sea. A gradual growth of a new delta took place during the whole period from 1970-s in spite of the sea level rise. Sediment discharges were so large that processes of sedimentation overpowered the effect of the sea level rise. A specific reaction to the sea level rise was found in the Ural River delta – formation of a wide reed belt in flooded part of the delta and, after the sea level rise exceeded 1.7 m – destruction of this reed belt. Even moderate fall of the sea level after 1995 (by 0.54 m to 2001) led to the growth of reed strips along the borders of the river channel at the mouth that shows the increase of the accumulative processes.

Investigated features of the Caspian river deltas dynamics can be used as an analogue phenomenon for prediction of processes, which can take place in the coastal zones and river deltas of the world in the case of proposed global significant rise of the sea level.

Keywords: delta change, sea level, river sediment yield, monitoring, space images, mapping