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International Journal of Marine Science 2014, Vol.4, No.43, 1-9
http://ijms.biopublisher.ca
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have been widely discussed in previous studies
(Firoozfar et al., 2011). Also, due to increasing
human activity and its impacts, the annual amount of
riverine sediment has risen from 10 to 40 tonnes
during the past decades. Rivers flowing from the
south into this sea are categorized into three groups
based on the morphology of their mouths and the
nature of river/sea dynamics (Lahijani et al., 2008):
(i) Flowing through lagoons and lowlands, now
ephemeral in nature due to increasing water
consumption recently.
(ii) Have a normal flow and mostly seen in steep
slope coasts; on moderately sloping coasts they are
slightly affected by long-shore currents of the sea
and some bars and lagoons are seen.
(iii) Great rivers with considerable sediment supplies
(Sefid-Rud River in the West and Gorgan-Rud River
in the East) producing deltas and mouth bars and
having high sediment discharges.
While great rivers expand their deltas, in some cases
small rivers locally impact coastal sediments and
pose problems for the locals. For example, during
the first survey, at a certain point in Kelachay, the
local fishermen talked about an obstacle at a depth
of around 2.5 m that would tear their fishing nets.
Later, in the third field survey, this problem was
investigated by divers. On this shore, fishermen
would cast their fishing nets in 3~5 m depths of
water and after a specified time would drag them out
with tractors to gather in the fish. By diving, it was
proved that this was a very thin, locally created layer
of cohesive clay probably formed by sediments
transported by several small rivers running close to
each other. While being dragged along the seabed,
the fishing nets must have been torn by this layer.
On-shore bars can show the dominant direction of
the sediment transport in some regions. They are not
seen in every region. They are mostly seen at the
coast at Guilan and eastern Mazandaran, while
nearshore sandy bars are formed in most regions,
except Golestan (Pers. Comm. with local people,
2009). Small and relatively large lagoons can be
seen in eastern Mazandaran and central Guilan.
Coastal sediments are mainly sand, except for at the
western Mazandaran coast in some segments of
which gravelly beaches can be seen, and on the
Golestan coast where coastal sediments are mostly
clay.
Considering shore sediments, southern Caspian Sea
coasts can be categorized into three groups: sandy
beaches, gravelly beaches and muddy beaches. In
Guilan and eastern Mazandaran, coasts are covered
with sand. In the western Mazandaran however, in
some segments – not the whole coastline – gravelly
beaches can be seen. The Golestan coast is
dominated by silt and clay.
For the whole Caspian Sea coast of Iran, nearshore
sediment is mostly sand except that of Golestan
where clay and silt dominates. One of the main
reasons behind this is the direction of long shore
currents. Generally, the southern Caspian Sea coasts
are exposed to waves which come from the north,
northeast and the northwest. The waves coming
from the north and northeast reach the western part
of the coastline, namely West Guilan, Central Guilan
and West Mazandaran, while the waves reaching the
eastern part including East Mazandaran and
Golestan come from the North and Northwest
(Lahijani et al., 2007). As a result of these waves,
longshore currents can be observed in a North-South
direction along the western and eastern coasts.
Along Iran's Caspian Sea coast a prevailing eastward
longshore current flows, which enhances the
eastward descending trend in the size of the
sediment. In some segments of West Mazandaran,
gravelly particles are seen even at depths of up to 4
m. Moreover, clay and silt particles can be observed
at different depths along the profiles.
Table 1 shows an increasing trend in the sediment
size from both sides towards the centre. Generally,
travelling from west and east towards the centre
sediments are increasing in size. Also, a decreasing
trend can be seen in the size of the sediments along
the beach profiles at all stations (Figure 5).
Furthermore, an interesting result emerges from
analysis of the deep sediment samples collected