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International Journal of Marine Science 2013, Vol.3, No.32, 253-257
http://ijms.sophiapublisher.com
254
Sefidrood River delta shows that rapid sea level
changing have direct influence on its evolution along
the Quaternary period (Alizadeh, 2007; Jedari, 2005).
It was determined that many rivers of study area were
connected to the Caspian Sea through marginal lagoon
and some of them enter to the sea directly (Alizadeh,
2007). So there are different conditions of estuaries
shapes, sedimentary depositions and morphodynamic
structures in the study area. So in this paper with
emphasis to geometry of beach structure, sediment
size distribution and morphodynamic formation we
want to compare main rivers of the study area together
and then their behavior would be controlled against
rapid sea level changing through satellite image
interpretation.
1 Material and Method
1.1 Study area
Caspian Sea as the largest surrounded basin in the
world is located between Eurasia Bridge and there are
five marginal countries along its coastal area. Its
watershed basin area is about 400.000 km square and
the maximum length of it is 1200 km and with
average wide approximately about 365 km. there are
many important rivers around the Caspian Sea, that
among them Volga is the vital river and it cover 75
percent of water entranced of the Caspian Sea
(Khoshravan, 2001). After that, Omba, Solak, Samour,
Atrak and Oral are important rivers in the Caspian
region. The southern coast of the Caspian Sea as study
area was elongated along the North-Alborz Mountain
and it has 865 km length. There are more than 100
rivers in this region that they discharge water and
sediment to the Caspian Sea (Figure 1).
Figure 1 Study area location map and main rivers of the
Caspian sea south coasts
1.2 Methodology
the main rivers of study area have been studied from
the amount of discharge of water and sediments to
Caspian Sea and then eight rivers were selected in the
southern coasts of the Caspian Sea: (Gorganrood,
Neka, Larim, Sorkhrood, Nashtarood, Sefidrood,
shafarood and Lisar) (Figure 1). They are covering all
part of study area from East to West ward. The
selection indexes of river depend on hydrological
condition of rivers and hydrodynamical and
morphological of the beach zones. In the second stage,
with field survey monitoring and sediments sampling,
all sedimentary–morphodynamic formation of beach
zone and estuary of rivers were measured. Samples
were collected from River mouth, around the beach
and at the back of rivers. Then after laboratory test
sediments grain size parameters were calculated with
analytical software. So the sedimentary characteristic
of rivers mouth were determined and classified by
obtained results. Subsequently the estuary shape of
main rivers of the Caspian Sea and river mouth
deformation have been comparing with use satellite
images associated to last Caspian sea level rise during
1983 till 2004. The images of 1983 year belong to the
aerial photos with scale 1:10000 and the satellite
images are from Landsat (TM), 2004 year were
georeferenced with topography map with 1:25000
scale and with use GIS software (Arc- GIS 9-2), all
vector data of rivers and estuary were prepared and
finally with comparison of them, the estuary deformation
along the above mentioned time was reconstructed.
2 Results
2.1 Sediments texture analysis
Comparing results of sediments grain size analysis
and sedimentary parameter evaluation (d50, Mean,
Skewness, Kurtosis, standard deviation) of all selected
river of coastal stations show that sediments textural
properties have varied between the mouth of rivers
and the adjacent coasts area (Table 1).
2.2 Estuary shape classification
it was known that selected river could be classified
from sedimentology index point of view. The kind of
sediments of study area change from very fine grain
sediments (clay to sandy clay) in the Gorganroud
River to very coarse gravel (pebble and cobble) in the
west of Gilan (Shafaroud and Lisar rivers). As
expected the transition modes have been observed