caspian sea river mouth evolution

1. International Journal of Marine Science 2013, Vol.3, No.32, 253-257
http://ijms.sophiapublisher.com
Research Article
Open Access
Caspian Rapid Sea Level Changing Impact on Estuaries Morphodynamic
Deformation
Homayoun Khoshravan , Masoumeh Banihashemi
Caspian Sea Research Center, Water Research Institute, Km 8 Khezerabad, Sari, Mazandaran, Iran
Corresponding author email: h_khoshravan@yahoo.com
International Journal of Marine Science, 2013, Vol.3, No.32 doi: 10.5376/ijms.2013.03.0032
Received: 05 May, 2013
Accepted: 03 Jun., 2013
Published: 12 Jun., 2013
Copyright © 2013 Khoshravan and Banihashemi, This is an open access article published under the terms of the Creative Commons Attribution License, which
permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:
Khoshravan and Banihashemi, 2013, Caspian Rapid Sea Level Changing Impact on Estuaries Morphodynamic Deformation, International Journal of Marine
Science, Vol.3, No.32 253-257 (doi: 10.5376/ijms.2013.03.0032)
Abstract In this paper, the evaluation of sedimentary-morphodynamic deformation of main estuaries of rivers in the southern
coasts of the Caspian Sea is main target. With selecting, eight main rivers and by sampling of sediments on them in the beach zones,
geometry of surrounded beach structure, morphodynamic condition and sedimentary deposition processes were analyzed. with
interpretation satellite and aerial images of study area along the period between 1983 till 2004 that correspond to last progression
phase of Caspian sea level arise (+ 2.5m), the effect of rapid sea level changing of the Caspian Sea on beach and mouth of rivers have
been measured. The results show that there are different type of the estuaries in the study area and the last sea level arise has caused
morphdynamic deformation (trait inclination of rivers, inflation of mouth and it’s widen) on the beach zone and the rivers mouth
condition. Therefore as conclusion, the rivers of the Caspian Sea southern coasts have different behavior against rapid sea level
changing in the coastal zones and they are classified to three statements: erosion, accretion and transition.
Keywords Caspian; River; Sediment; Morphodynamic; Fluctuation; Estuary
Introduction
the West part of Mazandaran province beach and East
of Gilan province shore. At the other hand the
South-Eastern coasts of the Caspian Sea (Bandar e
Torkaman) and the coasts in the West part of Gilan
have low energy statements (Alahmad, 1996). Other
coasts along the West part of Mazandaran central zone
have transition condition of energy level (Alahmad,
1996). Also the statement of hydraulic forces of rivers
is similar to hydrodynamic of sea. The rivers of study
area were classified to permanent and temporary
conditions considering the amount of water and
sediment discharge to the Caspian Sea (Khoshravan,
2001). From morphological point of view the southern
coasts of the Caspian Sea has been classified to five
zones (Khoshravan, 2000). Each of them has special
condition related to beach structure geometry and
morphodynamic and sedimentary condition (Khoshravan,
2000). as result of the beach response to environmental
forces. Therefore the shape of estuary and river mouth
completely was associated to surrounded morphological
zone. As previous research showed that the Southern
coasts of the Caspian Sea has been classified to three
hydrodynamic condition (dissipative, reflective and
transition) (Khoshravan, 2007). Also past study on
Morphodynamic structures figures in the estuary area
were associated to sedimentary depositional processes
and hydrodynamic of sea and hydraulic of river
(Lichter and Viely, 2010). The protection and
remediation of rivers in the coastal zone against to
erosion and destructing events and preventing of
environmental disturbances development on there
have required enough understanding on natural
condition of marine forces (waves, currents, storms)
and river discharge amount (Wright and Thom, 1980).
So in this research recognition and classification of
sedimentary-morphodynamic condition of rivers
mouth and its deformation situation against rapid sea
level changing is the main problem. Previous studies
results show that hydrodynamic and hydraulic effects
have special trait in study area (Alahmad, 1996). As
the annually regime of prevailing winds is very
different. So physical condition of wind-induce wave
in the coastal area is complex and different (Alahmad,
1996). This agent caused the energy of the breaking
waves would be dissimilar in the different part of the
southern coasts of the Caspian Sea (Alahmad, 1996).
Therefore wave dominated area has been spread along
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2. International Journal of Marine Science 2013, Vol.3, No.32, 253-257
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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.
1.2 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.
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).
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
Figure 1 Study area location map and main rivers of the
Caspian sea south coasts
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3. International Journal of Marine Science 2013, Vol.3, No.32, 253-257
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Table 1 The sediment grain size mean of sampled points
Grain size (backshore) mm
Grain size mean (Beach) mm
Grain size mean (Mouth) mm
Name of River
0.014
0.25
0.17
0.22
0.38
0.23
1.35
2.28
0.3
0.21
0.3
0.36
0.25
0.2
1.42
1.55
0.22
0.15
0.25
0.41
2.73
0.21
1.61
2.18
Gorganroud
Nekaroud
Larim
Sorkhroud
Nashtaroud
Sefidroud
Shafaroud
Lisar
and in the central part of Gilan coasts (Gorganroud
and Sefidroud rivers) have certain developed delta.
Instead of there is no delta in the West of Mazandaran
and West of Gilan beach zones (Nashtaroud, Lisar and
Shafaroud rivers. The traits of Rivers of central of
Mazandaran have been inclined near to shore
(Nekaroud and Larim Rivers). Also some mouths of
rivers of West of Mazandaran and Gilan have been
barred with fluvial coarse grain sediments (Nashtaroud,
Lisar and shafaroud Rivers). And many of them have
been widen in the central part of Mazandaran coasts
(Larim Rivers).
with fine to medium or coarse sand in the central of
Mazandaran and Gilan coasts (Sorkhroud, Sefidroud,
and Nekaroud Rivers). Also the comparing results of
sediment size of rivers mouth and surrounded beaches
determined that there is much dissimilarity between
coastal sediments and estuary. For instance: in the
Sefidroud estuary, all sediments in the beach belong to
rivers and it could be covered vast area of beach zone.
At the other hand shore sediments of the Caspian Sea
have covered the rivers mouth in the Nekaroud and
Larim Rivers. But there are transition condition near
to Sorkhroud and Nashtaroud rivers that sea and rivers
sediments cover the coastal zone together.
2.4 Rapid sea level fluctuation and estuary deformation
Satellite images periodic comparing results show that
the last sea level rose as 2.5 m elevation from 1984 till
2005 could be change the estuary condition and mouth
of rivers shape in the study area. As related to
steepness of beach and kind of sediments covering in
the determined morphological zones, the shape of
mouth of rivers has been changed at the different
types. For instance territory of Gorganroud and
Sefidroud Rivers near to beach zone have been limited
by sea level progression. Also the rapid penetration
of sea water to rivers has caused the several
morphodynamic formation changing (widen and
displacement of mouths). And in the other part of
study area kind of estuary response is different and
wider mouth could be observed on there. For instance
in the Nekaroud estuary territory the mouth of river
was displaced toward beach about 135 meters and the
wide of mouth is increased along the sea level rise
(Figure 3). Of course in the high steepness beach zone
like Sorkhroud shore, the river territory could not be
affected by sea level raised.
2.3 Estuary shape classification
On the basis of obtained results of field monitoring
and satellite image analysis the rivers mouth of study
area have been classified to the kind of barred,
swollen, widen, inclination, tighten, deltaic and non
deltaic estuaries (Figure 2). The rivers of south eastern
of the Caspian Sea in the Gomishan-Badar e Turkmen
Figure 2 the Variety of Rivers mouth shape in the study area
3 Discussion
Note: a: inclined mouth, b: tighten mouth, c: widen mouth, d:
Major coastal sediments of the study area were
originated from the rivers, among them Sefidroud,
barred mouth, e: deltaic mouth, f: inflation mouth
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4 Conclusions
As conclusion there is real direct relationship between
beach steepness and sediment size distribution. The
comparing of sedimentary parameters data of selected
stations show different result from natural condition of
sediments point of view. And with apply sediments
sorting, d50, mean, skewness, kurtosis as indicator the
estuaries of the southern coasts of Caspian Sea have
been order to:
Well sorted coarse grain sediments (Nashtaroud River)
Bad sorted coarse grain sediments (Shafaroud and
Lisar Rivers)
Figure 3 The rapid sea level changing impact on rivers mouth
deformation in the study area
Well sorted fine to medium sand (Sorkhroud, Neka
and larim Rivers)
Haraz and Gorganroud are very important rivers and
have special significance. The Rivers of the Caspian
Sea southern coasts were classified to two orders:
Meandering and braided Rivers (Khoshravan, 2001).
Field survey result determined that braided rivers
usually have short trait and their mouth were covering
with coarse fluvial sediments in the western part of
Mazandaran and Gilan morphological zones. And
meandering rivers at the near beach zone have long
traits and they discharge fine sediments (sand, silt and
clay) to coastal zone in the central region of Gilan and
Mazandaran morphological zones. The Iranian Rivers
which enter to Caspian Sea have watershed basin with
135,000 km square and annually they charge
40,000,000 tons sediments to the Caspian Sea.
Hydrology data evaluation associated to rivers shows
that during many recent decades, with human activity
developed as dam making caused that the amount of
sediments of rivers decreased about 10 to 40 percent
(Khoshravan, 2001). Also hydrodynamic of Caspian
Sea in the study area has no stable situation seasonally
and it varied along the southern coasts of the Caspian
Sea (Khoshravan, 2007). So this region of the Caspian
sea from hydrodynamic effect to beach zone have
been classified to dissipative, reflective and transition
beach (Khoshravan, 2007). Also sediments of study
area were breakdown to three type regime (coarse
gravel, sand and very fine grain of clay) (Khoshravan,
2000). It is interesting that the beach zone sediments
were following from nearshore morphodynamic and
variety of rivers. As at the high slope shore, usually
coarse grain of sediments was deposited and reversely
at the low steepness beach, fine sediments have been
dominated.
Bad sorted very fine sand and clay sediments
(Gorganroud and Sefidroud Rivers).
The hydrodynamic and Hydraulic energy level is
different between above classified estuaries. As in
Nashtaroud and Sorkhroud waves and currents have
been well developed and river effect is low to
sediment distribution and here is wave dominated
region. At the other hand in the Gorganroud and
Sefidroud territory sediments of rivers cover all part of
beach zone and there are active deltaic sedimentary
deposition. So these areas are called to River
dominated region. Hydrodynamic impact is very low
degree around them. Of course the Lisar and
Shafaroud Rivers are following as same statement. As
the field monitoring and satellite image analysis
results show that erosion processes associated to sea
have caused estuaries shape deformation like:
declination, tighten, widen, barred and inflation of the
mouth of rivers. And at the other hand in accretion
coastal zone with high hydraulic energy, other type of
morphodynamic formation like Delta and sand bar
have been created (Dan and Janr, 2011). In the
transition beach zone the estuary shape could be
change differently with common effect of rivers and
sea forces. Usually at this place sand spits were
originated by double impact of river and sea (Dan and
Janr, 2011). Finally on the basis of morphodynamic
index, the estuaries of southern coasts of the Caspian
Sea have been breakdown to three types as following
mentioned:
Erosion estuaries (Nashtaroud River)
Accretion estuary (Gorganroud, Sefidroud, Shafaroud
and lisar Rivers)
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Dan S., and Janr D., 2011, Processes controlling the development of river
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Khoshravan H., 2001, Sedimentary processes and hydrodynamic in the
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Transition estuary (Sorkhroud, Larim, Nekaroud Rivers)
Therefore as final conclusion we showed that
sediments size distribution and morphodynamic
formation is a good indicator for estuary classification
in the study area. Also rapid sea level changing of
Caspian Sea has a direct influence on rivers mouth
deformation and the tendency of changeable events
associated to estuary depend on sea and river forces
and type of beach zone from geometry of beach
structure point of view.
References
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Alizadeh H., 2007, The morphology of Iranian Rivers at the fluctuation and
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