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 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 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.

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.

Table 1 The sediment grain size mean of sampled points

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 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).

Figure 2 the Variety of Rivers mouth shape in the study area

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.

Figure 3 The rapid sea level changing impact on rivers mouth deformation in the study area

Wright L.D., and Thom B.G., 1980,. Wave influences on river mouth depositional process, Estuarine and Coastal Marine Science, 11: 263-277
http://dx.doi.org/10.1016/S0302-3524(80)80083-1