Environmental consequence of Caspian rapid sea level changing in Gorgan Bay
Homayoun Khoshravan
1
, Alireza Naghinejad
2
1
Head of environment research management institute, science research and technology ministry
of Iran
H_khshravan@yahoo.com
2
Associated professor of faculty of science of Mazandaran University, Iran
anaqinezhad@gmail.com
Keywords: Gorgan Bay, Caspian Sea, environment, fluctuation, morphlogy
Introduction:
The global warming issue is an absolutely accepted concept of the Antropocene stage. Moreover it
has been predicted that due to 3 degrees increment of globe temperature by 2100, the
vast parts
of crowded coastal cities with their all social and economic infrastructures will be disappeared and
inundated (Feng, 2014). This is despite the overall hydrologic response of inland seas, lakes, ponds,
side bays in northern parts of Africa, Middle East and some other parts of the globe, which act
differently from free ocean water bodies (Khoshravan & Vafaie, 2016). As global temperature
increment leads to the growth of evaporation rate and precipitation reduction and finally causes
the drought trend development, through mentioned regions. Namely, it can be
pointed to the
drought of vast parts of the inner lakes of Iran plateau as Urmia Lake, Parishan, Maharloo and
Hamoon. The Caspian Sea basin as the biggest closed watershed in the world also has followed the
similar destiny and illustrates the impacts of global warming with various ranges during the 20
th
century Kroonenberg & et al (2000). Nowadays the Gorgan bay as one of the Caspian Sea
dependent water resources has lost vast parts of its water supplies due to drought procedure.
Therefore the main objective of the current study is the evaluation of morphological of Gorgan bay
due to water level
fluctuations Caspian Sea, because of global warming, and illustration of
effective and practical solutions in order to get rid of current situation of the bay. The Gorgan bay
watershed is one of the most important southern catchments of Caspian Sea basin with an area
about 15000 Km
2
which consists of mountainous, sub mountain regions, and coastal plains
(Alizadeh, 2010). According to the wetlands classification conducted in Ramsar convention (1975),
the Miankaleh wetland and Gorgan bay were
classified as type A, the permanent shallow sea
water bodies. The precipitation range is decreasing along west-east direction (from 800 mm up to
450 mm). The Gorgan bay is located at the southeastern part of Caspian Sea and lies in west-east
direction parallel with shoreline (fig1). At the moment, the length of the bay is 44 Km and it’s
width at the widest section is about 12 Km. the area of Gorgan bay is 360 Km
2
and its maximum
water depth is evaluated about 4 m.
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Fig 1- Gorgan Bay and Miankaleh Lagoon location map
Materials and methods:
The current study has been conducted on the base of scientific documentations, field studies,
evaluation of coastal sediments and satellite images interpretation. At the first step, the creation
of the bay and the most important factors of its morphological evolution have been rebuilt due to
geological evidences. The deformation rate of Gorgan bay coastal line
during various fluctuations
of Caspian Sea has been evaluated by comparing the satellite pictures of 1966, 2004, and 2016
years. The energy level and important flows in sedimentation process in main inlets, as important
factors of depository environment evaluation, have been evaluated by the help of sedimentology
studies. The adaption ways with natural circumstances and global warming phenomenon have
been finally presented.
Results:
The classification of sedimentary environments of Gorgan bay
The field studies have shown the various sedimentary environments in Gorgan bay and Miankaleh
peninsula. The most important regions are as follows: wetlands, muddy zones, salty marshes,
deltas, communication channels, and the sandy coast of sea, the intermediate zones between sea
and wetlands, and sand dunes. As a general point of view, the Gorgan bay sedimentary
environments are classified as follows:
-
Paludal
sediments, including dark clays with high organic materials, full of Mollusks lime
shells ( gastropods and bivalves)
-
Sandy spit sediments, including well sorted brown reddish sands, with bivalve shells)
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