THE ROLE OF ERRATIC SEA-LEVEL CHANGES ON THE EVOLUTION OF A COASTAL WETLAND WITH THE EXAMPLE OF LAKE ANZALI, NORTHERN IRAN

The modern Lake Anzali with a maximum surface of 160 km2 and maximum depth of 5.5 m is the largest freshwater coastal wetland of northwestern Iran. It is connected and/or discharges to the Caspian Sea with a partly regulated 3.5 km long channel. A Late Holocene prograding beach-ridge complex and recent beach sediments separate the lake from the sea. The surface of Lake Anzali, which receives water and sediments from fifteen rivers originating from the Alborz Mountains, is only 2 m above the mean level of the Caspian Sea (presently it is at 26 m below oceanic level), consequently sea water can temporarily enter into the lake during high storms or when the Caspian level permanently increases. This recently took place in 1991-1996 with a doubling of the lake area. In spite of apparent sedimentation in the lake, the coastal zone was eroded on c. 30-100 m. The records show that the highest sea level was in 1930 at –25.25 m and then dropped to –27.00 m in 1945. The decrease gradually continued to –28.20 m in the following 30 years. Later it increased erratically up to 2.5 m from –28.44 m of 1977 to –26.29 m of 1996. In 2000, it was at –26.36 m. The recent development shows that Late Holocene evolution of Lake Anzali and its surrounding has been closely linked to Caspian Sea level fluctuations. The beach ridge prograded most probably during a sea level decreased.