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International Journal of Marine Science 2013, Vol.3, No.22, 173-177
http://ijms.sophiapublisher.com
174
(Amini et al., 2012). Sediments resources conservation in
coastal management programs with protective
properties such as berm zone and sand dunes are very
important. So in this research at the first step the
current situation is considered highly vulnerable to
erosion and at the next step its extent should be
estimated. The severity of the sand dune erosion
vulnerability never has been done in the GIS
environment yet. So it is expected that this research
could provide good answer for recognition of beach
susceptibility and vulnerability against human impact
and rapid sea level changing of the Caspian Sea.
The Study Area
The study area is located in the coastal area in the
southern part of the Caspian Sea, between Gomishan
City, in the far East to the coastal area of Astara in the
far West. This extensive area with the approximate
length of 807 km, has special coastal morphological
features that with regard to the northern skirts of
Alborz, Mazandaran and Gilan Plain, underwater
precipices, overlooking the southern trench of the
Caspian Sea, has created a varied morphological
aspect in the coastal line. Dynamic sedimentary
processes and hydrodynamic in this area have resulted
in the formation of different coastal line (erosive-
sedimentary), (steep - low slope), (coarse fine gravel-
fine grained clay) in various parts of the southern
coasts of the Caspian Sea that each of them is known
as the coastal morphodynamic features, reflecting the
natural property of its own coastal area.
1 Materials and Methods
At first the south coast of the Caspian Sea sediment
morphodynamic and divisions in the dry coastal sand
dunes were evaluated and eligible areas were
identified. Then the spatial and temporal changing
condition of sand dunes was studied with the help of
aerial images. The sand dunes variation were compared
with periodic satellite images associated with the last
Caspian sea level rises during 1983-2004. The images
of 1983 belong to the aerial photos with scale of
1:10000 and the satellite images are from Landsat
sputnik (TM), year 2004 were processed with
topography map with 1:25000 scale and with use of
GIS software (Arc-GIS 9-2), all vector data of sand
dunes were prepared and finally their comparison
resulted in the identification and measurement of the
sand dunes deformation along the mentioned period.
Then coastal protection vulnerability was processed
and analyzed by universal ranking model (URSM) in
GIS environment. In this model each index of sand
dunes associated with important degree and frequently,
has been graded and each object was given a special
normalized number (Table 1). Then the final degree of
vulnerability tendency of sand dune erosion was
calculated by overlaying processing on several
numbers of categories of sand dune. Finally with
classification of study area to 432 zones with 20 meter
wide and popularization of each number on them, the
erosion vulnerability tendency of the southern coasts
of the Caspian Sea was measured. In the next step, on
the basis of vulnerability model results the erosion
condition of sand dunes, were monitored in the study
area. The shape and variety of each sand dune has
been controlled and the level of erosion impact on
them was analyzed.
2 Results
2.1 Spatial and temporal changes of sand dunes
Results of the aerial and satellite images interpretation
show that the southern coasts of the Caspian Sea
region lack some forms of sand dunes and the other
sand dunes in some areas are pristine and untouched.
The sand dunes were dominant in the Caspian regions
of Gilan and central part of Mazandaran as the longitudal
dune shaped and in parts of east-central Mazandaran are
transverse or crescent shaped. Frequent sand dunes have
developed in the Mazandaran province. The coastal
provinces of Gilan and Golestan are in the second
place without the certain sand dunes (Table 2). Field
Table 1 Value important degree and frequency of several kinds of sand dunes of the Caspian Sea, southern coasts
Normalized number
Value degree
Frequency (%) Length(km)
Kind of sand dune
4
1
12.1
97.86
Pristine sand dunes
3
0.75
3.4
27.86
Discontinuity sand dunes
2
0.5
9.0
73.04
Tabulate sand dunes
1
0
75.5
667.98
Without sand dunes
Fuzzy set value degree classification
100
865
Total length of the study area