MORPHOLOGICAL CHANGES OF BARRIER-LAGOON COMPLEXES ASSOCIATED WITH SEA LEVEL FLUCTUATIONS IN NORTHEAST OF CASPIAN SEA

The Caspian Sea (CS), whose main characteristic is isolation from open oceans, as the world’s greatest enclosed water basin revealed a complete sea-level cyclewith an amplitude of around three meters over the last century, which included stages of regression (1929-1977) and transgression (1978-1995) [1,2]. Based on satellitealtimetry data, the CS basin is experiencing a decreasing trend in water level during the recent years (Fig. 1). Shoreline evolution patterns, morphological changes ofbarrier-lagoon systems and beach-ridge emergence/submergence are the most common coastal responses to water level fluctuations at low-lying coastal segments [3]. The Gorgan bay and Gomishan lagoon, the major geomorphologic features in the southeastern of the CS, are formed behind the barrier-spit and recognized asareas of high terrestrial biodiversity, rich marine, natural habitat for migratory shorebirds, and social tourist value. The southeastern Caspian coast is characterized by beachwith very mild slope both offshore and onshore that prevents high waves from approaching the shore and hence fine-grained sediments mainly consist the composition ofbed material of the beach.