caspian sea erosion vulnerability

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Quaternary International 167–168 (2007) 35–39
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Homayoun KhoshravanÃ
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Beach sediments, morphodynamics, and risk assessment,
Caspian Sea coast, Iran
Coastal Management Department, Caspian Sea National Research and Study Center, Water Research Institute, Zafar Alley,
Emam Square, Sari, Mazandaran, Iran
Available online 2 March 2007
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Abstract
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Protection of ocean and marine coastal regions is a vital part in any coastal management program for sustainable development.
Erosion processes have developed in areas with high population density and economic exploitation. Hydrodynamic forces (waves and
currents) are important agents for changing coastal processes and advancing erosion. This paper discusses coastal erosion vulnerability
along the southern coasts of the Caspian Sea. Evaluation of beach erosion and instability and assessment of hazards are the most
important objective. This research focused on six selected stations, each including six sites, with measurements in October 2004.
Sedimentary samples and beach geometric characteristics have been measured at all 36 sites. A Universal Ranking System Model
(URSM) was created by defining indexes including characteristics of all factors potentially contributing to beach erosion risk. A value for
erosion potential was assigned to every index, and Fuzzy theory was used to translate linguistic phrases to mathematical language. All
data pertinent to beach erosion was input into Arc View GIS, and the URSM ranking model applied. As a result, the relative risk of
erosion at each beach was determined. By dividing the study area into five morphological zones, zones with high vulnerability were
highlighted. Erosion and shoreline changes by hydrodynamic processes vary from region to region in the Caspian Sea. The Miankaleh
area along the southeastern coast is the most stable area, and Nashtaroud region in western Mazandaran is the most vulnerable area
along the southern Caspian Sea coast.
r 2007 Elsevier Ltd and INQUA. All rights reserved.
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1. Introduction
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The Caspian Sea, as the largest lake in the world, has
some important characteristics pertaining to sustainable
development. Biodiversity in the region is significant.
Water resources, substrate minerals and petroleum and
gas reservoirs are concentrated around the coasts of the
Caspian Sea. Natural agents, including climatologic and
hydrodynamic impacts, have caused economic damage
over time. Sea-level rise and storm waves result in erosion
in the coastal areas. Hazards and vulnerability have
increased in this region.
Insufficient knowledge of coastal components and
environmental forces (e.g. sea-level change and hydrodynamic impact) create serious problems for engineering
applications to coastal management. The improper design
ÃTel./fax: +98 151 2261405.
E-mail addresses: homayoun@umz.ac.ir, h_khoshravan@yahoo.com
(H. Khoshravan).
of engineering protection structures in coastal areas
and the high costs of preventing damage are among
the most important problems along the southern coast
of the Caspian Sea. Previous episodes of relative sea-level
rise from 1978 to 1996 caused very hazardous conditions,
impacting the socio-economic character of the region.
As a result, the assessment of relative vulnerability of
the Caspian Sea southern coasts was initiated to identify
the general structures and the natural essence of the coast.
On the basis of previous research results (Khoshravan,
1998), the southern Coasts of the Caspian Sea have
been classified into five morphological zones (Golestan,
Central Mazandaran, Western Mazandaran, Central
Gilan, Western Gilan) (Fig. 1). Each morphological zone
has certain morphodynamic characteristics considering
beach structure geometry, sediment erosion processes,
and morphodynamic formation. Environmental forces
(waves and currents) and beach response to different
conditions are the most important parameters for beach
erosion vulnerability assessment. By comparing the degree
1040-6182/$ - see front matter r 2007 Elsevier Ltd and INQUA. All rights reserved.
doi:10.1016/j.quaint.2007.02.014

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H. Khoshravan / Quaternary International 167–168 (2007) 35–39
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Fig. 1. Morphological zones along the southern Coasts of the Caspian Sea.
of vulnerability in these zones, critical areas and hazardous
regions can be identified.
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The Caspian Sea is the world’s largest inland sea in term
of both area and volume. The drainage basin extends from
361N to 621N and covers about 3.1 million km. Major river
inputs include the Volga (contributing up to 80–85% of the
total), Emba, Ural, and Terek rivers (Rodionov, 1994). The
relatively low salinity of the Caspian Sea surface water, and
the substantial salinity gradient from north (freshwater) to
south (brackish) (Kosarev and Yablonskaya, 1994), results
in the variety of endemic zooplankton and phytoplankton
species (Kasymov and Rogers, 1996). The history of the
Caspian Sea falls into a series of stages determined by
orogenic and climatic events. During the late Miocene, the
fully marine Caspian and Black Seas were connected by a
deep waterway, and the Black Sea was connected by a deep
waterway to the Mediterranean Sea as part of Paratethys
(Dercourt et al., 1985). In the middle Pliocene, orogenic
activity separated the southern part of the Caspian Sea
from the Black Sea. Later, they were temporarily
reconnected, and the Caspian Sea was part of the slightly
salty Pontic Lake. The Caspian Sea was connected to the
Aral Sea during the Pliocene and Pleistocene as the result
of major transgressions linked to large-scale influx of
meltwater from high-latitude ice caps (Grosswald, 1993;
Mamedov, 1997; Dumont, 1998). For the last 300 ka, the
Caspian Sea has existed as an isolated water body (Boomer
et al., 2000), with some short transgressive episodes
associated with interglacial periods and global sea-level
changes (Svitoch et al., 2000). The Amu Darya and
Sarykamysh Rivers have occasionally flowed from the
Tien Shan and the Aral Sea, respectively, to the Caspian
Sea during the Holocene. Today, the Black and Caspian
seas are connected via the artificial Don-Volga canal,
causing some faunal and floral exchanges. The northern ice
sheet during melting phases changed the amount of fresh
water reaching the Caspian Sea. The meltwater influx must
have governed the change of the Caspian from a freshwater
lake to a more saline water body. The last change from
freshwater to brackish conditions may have happened
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2. Caspian Sea
10,000 years ago (Mamedov, 1997). The Caspian basin
area is subdivided into three sub-areas: the northern
(80,000 km2) with average depth 5–6 m, and maximum
depth 15–20 m; the middle (138,000 km2) with a maximum
depth of 788 m; and the southern (168,000 km2) with an
average depth of 325 m. The southern basin holds more
than 65% of the Caspian Sea water and reaches a
maximum depth of 1025 m. A north–south gradient of
salinity is observed, with freshwater in the northern end of
basin to almost homogeneous 12.5–13.5 surface water
salinity in the central and the southern basins. In the
southern basin, seasonal salinity changes are less than
0.2–0.4. Mean annual salinity increases from the surface to
the bottom waters only by 0.1–0.3 (Zenkevitch, 1963;
Kosarev and Yablonskaya, 1994). Surface water temperature data record important seasonal variations. The
surface, less saline waters of northern basin freeze from
December to March (Zenkevitch, 1963). Mean water
temperature reaches 24 1C during July and August
(Kosarev and Yablonskaya, 1994). In the southern basin,
water temperatures vary from 9 1C in winter to 26 1C in
summer (Zenkevitch, 1963). There is a sharp thermocline
between 20 and 40 m depth during the summer, with
seasonal temperature fluctuations of the deeper waters
(4.5–6 1C below 200 m) almost negligible.
Surface waters of the southern basin are near oxygen
saturation in summer (94%) and slightly supersaturated in
winter (104%) (Zenkevitch, 1963). The dissolved oxygen
content decreases with depth, reaching 50% saturation at
200 m and o10% below 600 m but anaerobic conditions
are never reached even in the deepest waters. Most
nutrients enter the Caspian Sea in the northern basin via
the Volga River. Today, the relatively low nutrient levels
are depleted in the upper 100 m by phytoplankton activity,
but they increase with depth. Concentration of nutrients in
the northern basin is presently lower than prior to
regulation of the Volga River in the 1950s, except for the
silicate group (Kosarev and Yablonskaya, 1994). The
Caspian Sea is characterized by a high level of endemism
(Dumont, 1998) with modern assemblages derived from
three sources: Mediterranean Sea, Arctic, and river input.
The Caspian Sea biota ranges from freshwater to brackish
to euryhaline and has a low diversity. In general, marine

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H. Khoshravan / Quaternary International 167–168 (2007) 35–39
species comprise 72.1% of zooplankton. Surveys of surface
water of the Caspian Sea have recorded about 440
phytoplankton species, the northern basin containing the
highest diversity (Kasymov and Rogers, 1996).
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The general morphology of the coastline was assessed,
using study of local maps and satellite images. Field work
determined the morphological characteristics of the shorelines, and involved sampling of sediments. Field activities
and marine monitoring were done along six transects in
dry coastal areas and nearshore regions of Miankaleh,
Sorkhrood, Nashtaroud, Anzali, Talesh, and Astara
(Fig. 2). After field measuring, sediment sampling and
laboratory processing, a large volume of data was
produced. Thus, it was necessary to develop a universal
system that included all the information and make the data
comparable and assessable. A Universal Ranking System
Model (URSM) was developed, so that by inputting
physical properties (sediment, morphodynamics, and beach
structures), relative vulnerability could be determined. In
developing the URSM, for translation of all data of several
kinds (digital, maps, graphs, etc.), the theory of Fuzzy sets
is a useful technique for translation of data to mathematical language. A Fuzzy set in a universe of discourse U is
characterized by a membership function mA(x) that takes
values in the interval [0, 1]. Therefore, a fuzzy set is a
generalization of a classical set which allows the membership function to take any values in the interval [0, 1]. In the
URSM, indices were defined for every kind of beach
physical property. The indexes defined for beach structure
vulnerability include: beach and nearshore zone geometry,
considering steepness, width, length of berm and beach
face and shoreline in the arid zone and also in the shore
zone to about 10 m depth. For sediment instability,
important sedimentary parameters include size distribution, sorting, mineralogy, and specific gravity. Important
morphodynamical structures include erosional berms,
cusps, bars, and dunes.
A weighting factor between 0 and 1 was assigned to
every index. Fuzzy set theory was applied to the data, with
the indices related to every kind of beach vulnerability
degree included, and the weighting factor for every index
was the membership function of the index (m) in that set.
Significance values assigned to all components of beach
vulnerability composed a second Fuzzy set.
Application of the URSM to the data used Arc View
GIS 3.1 software. Overlaying is a traditional method in
environmental assessment. In this method, information for
an array of variables is collected for standard geographical
units within the study area, and recorded on a series of
maps, typically one for each variable. These maps are
overlaid to produce a composite. The resulting composite
maps characterize the area’s physical, social, ecological,
land use, and other relevant characteristics. All data were
introduced into the GIS, and three information layers
presenting location and attributes of the beach vulnerability created.
The relative vulnerability to erosion of each beach was
determined. By dividing the study area based on geomorphologic units, and computing risk and vulnerability for
each, the total vulnerability degree was calculated for the
study area. By overlapping several ranking degrees
determined from the data for each station, and by
comparing rankings, a final sediment erosion vulnerability
map was produced.
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3. Methods
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4. Beach structure geometry
Measurement of beach structure geometry is a very
important parameter to assess beach response to erosion.
At the six stations along the southern coast of the Caspian
Sea (Miankaleh, Sorkhrood, Nashtaroud, Anzali, Talesh
and Astara), all beach structure geometric characteristics
were measured in the dry beach and nearshore zone (from 1
to 10 m depth).
The most important geometric elements are berm
conditions (elevation, width, distance to shoreline, slope),
beach face, and shoreline slope. In the nearshore zone,
parameters measured included slope of sea floor at various
depths (1, 2.5, 5, 7, 10 m). Measurements show that beach
structure is different at each station. Nashtarood and
Anzali, with steep slopes in the beach and nearshore zone
have high vulnerability. Other stations, such as Miankaleh
and Astara, have gentle slopes in these areas. The southern
coasts of the Caspian Sea are classified as follows:
Fig. 2. Sample areas, southern Coasts of the Caspian Sea.
Coasts with steep slopes on the beach and nearshore
zone (Nashtarood, Anzali).
Coasts with steep slopes on the beach and gentle slopes
in the nearshore zone (Talesh, Astara).
Coasts with gentle slopes on the beach and steep slopes
in the nearshore zone (Sorkhrood).
Coasts with gentle slopes on the beach and in the
nearshore zone (Miankaleh).
Therefore, the resistance of these coasts to hydrodynamic
impact and erosion would be different. The sensitivity to

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H. Khoshravan / Quaternary International 167–168 (2007) 35–39
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erosion increases progressively from Miankaleh, to Astara,
Talesh, Sorkhrood, Nashtaroud, and Anzali.
5. Natural condition of sediments
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The second important factor for evaluation of vulnerability along the southern coasts of the Caspian Sea is the
natural condition of the sediments. Beach stability depends
on sediment texture and composition. Coasts with coarse
sediments are generally more stable than those with finer
sediments Beaches. The composition of sediment is very
important considering chemical erosion. Sediment samples
were obtained extending from the shoreline to 10 m depth
(0, 1, 2.5, 5, 7, 10 m depth) at the six selected stations. All
sediment samples were analyzed for size distribution,
specific gravity and clast shape. Sediment size parameters
measured include mean, d50, skewness, kurtosis, and
standard deviation. Microscope study evaluated roundness, sphericity, erosion scars, sorting, and mineral
composition. The southern coasts of Caspian Sea have
been classified as
Fig. 3. Vulnerability grade, southern Coasts, Caspian Sea.
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Therefore, the rate of sediment resistance to erosion
decreases progressively from Sorkhrood, to Nashtarood,
Anzali, Talesh, Miankaleh, and Astara.
6. Morphodynamic formations
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Morphodynamic formations are created by beach
response to hydrodynamic impact. Erosion and instability
are evaluated using coastal zone morphology (Short, 1999).
This allows assessment of marine forces and hydrodynamic
energy level. Along the southern coasts of the Caspian Sea,
the most important morphodynamic formations are cusps,
erosional berms, erosional embayments, and beach stratification. On the basis of field observations, the Caspian Sea
southern coast has been classified as
Therefore, the degree of vulnerability progressively
increases from Talesh, to Astara, Miankaleh, Anzali,
Sorkhrood, and Nashtarood.
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Coasts with coarse well-sorted sediments and high
percentages of heavy minerals (Anzali).
Coasts with coarse moderately sorted sediments and
high percentages of heavy minerals (Nashtarood).
Coasts with well-sorted medium sediments and low
percentages of heavy minerals (Sorkhrood).
Coasts with fine well-sorted sediments and high percentages of friable minerals (Miankaleh).
Coasts with fine poorly to moderately sediments and
moderate percentages of heavy minerals (Astara).
Coasts with very coarse, poorly sorted sediments on the
beach and fine, moderate to well-sorted sediments in the
nearshore and high percentages of heavy minerals
(Talesh).
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Coasts with moderate morphodynamic formations such
as erosional berms with moderate elevations, and
moderate wavelength cusps (Anzali, Sorkhrood).
Coasts with small morphodynamic formations such as
erosional berms with low elevations and short wavelength beach cusps (Miankaleh, Astara, Talesh).
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Coasts with mega morphodynamic formations dominated by erosional berms with high elevations, long
wavelength cusps and erosional embayments (Nashtarood, Ramsar).
7. Conclusion
The main results suggest that the sensitivity of Caspian
Sea southern coasts to environmental forces in several
regions, based on different conditions, differ substantially.
Through collation of the available information, the GIS
identified that sensitivity increases progressively from
Astara to Miankaleh, Talesh, Sorkhrood, Nashtaroud,
and Anzali (Fig. 3). Prevention of natural crisis relating to
changes in sea level and its hydrodynamic impact requires
consideration of the sensitivity of specific coastal regions.
Several development applications (commercial, industrial,
residential, agricultural) must be reconsidered, and the
limit of marine action must be identified. It is necessary to
construct structures to protect coasts using a sound
engineering strategy.
Acknowledgments
This work is part of the program of Caspian Sea
National Research Study Center (CSNRSC). We
acknowledge all colleagues who organized and participated
in the sea cruise (October 2004), during which the sediment
samples were collected with the help of the Fishery
Research Institute of Iran. We are grateful to Mr. Javad
Malek (Head of CSNRSC) and others for their helpful
comments.

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