The morphologic structure of coastal area of seas and lakes depends on different parameters: the geological and tectonic nature, the water level fluctuations, waves, boundary currents, climate conditions, and type of deposition sites and sediments (Khoshravan 2007). As a result, the zoning of coastal areas are conducted on the base of production mechanisms and origins of sedimentary materials and internal - external effective forces in transferring the sedimentary cells (Horikawa 1988). The morphodynamic behaviors and reactions of coastal areas are depending on coastal morphological features, the condition of sedimentary basin and hydrodynamic forces (Horikawa 1988). On the base of mentioned factors, different sedimentary environments have been shaped such as: sandy beaches, mud flats, cliffed or graveled coasts, and sandy dunes (Horikawa 1988). The principal question in current study is to identify the morphological units of coastal areas and Urmia lake bed. In this regard, the results of previous researches have illustrated that the topographic type of Urmia Lake bed and beaches is not normal (Khoshravan 2014). As the spatial distribution of heights up to coastal line in different parts is not similar and also the lake bed depth increases along south to north. The primary bathymetry studies on Urmia Lake, have illustrated that various sedimentary structures have been shaped by hydrodynamic forces in different parts of lake bed (Keltz and Shahrabi 1986). Besides, the obtained results from evaluation of sub bottom sediments have confirmed the existence of various sedimentary facies such as detrio clastic, chemicals, biochemical and organic materials in sedimentary sequences of upper Pleistocene in Urmia Lake. Moreover, it has been approved that the origin of 25 to 40 percent of detrio clastic sediments in the lake, belongs to runoffs and winds, and 60-75 percent of other sediments have chemical and biochemical origins (Amini 2009). In current study all geomorphological coastal and lake bed types in Urmia lake basin will be identified and zoned by the help of scientific evidences such as: topographic maps, hydrography curves, geophysical profiles and field research.

Lake Urmia is the largest lake in the Middle East and the second largest salt lake on earth. It is located lat 37^o to 38.5^o N, long 45^o to 46^o E. The Urmia Lake with the area over 5000 square kilometers is one of the most considerable morphotectonic structures in Iran plateau. The length of the lake is 125 km and its width is estimated 15 to 50 km, and also the average width is 40 km (Figure 1). The area of the lake is variable due to water level, and presently because of wide drought effects, the average depth is about 1.5 meters (Khoshravan 2014). Diverse topographical features around the lake, which involve high mountainous regions with cliffed structures up to low hill slopes and also mud flats, give special sight to the region (Seivani 1990). As the mountainous regions around the lake with elevated mountain tops and thin soil profiles, mostly have no vegetation cover. Some of the important heights overlooking the lake are Islami peninsula in east, Zanbil Mountain in west, the rocky hillsides of Govarchinghaleh region in northwest, also central and southern mountains in lake located in southern Islands (Figure 2). There are hill slopes in west coastal parts of Urmia Lake which are spread along north-west and south-east directions, and their plain and sub mountains slopes are relatively high. The expanse of lake coastal parts adjacent to mentioned areas are quite limited. In some western parts of Urmia Lake, the heights of mountains reach over 3,000 meters. Sahand volcano with 2,500 meters height from the sea is located at the eastern part of Urmia Lake. The evaluation of bed slope and the distribution of bathymetry shows that the lake is divided to deep and subsiding northern parts and also shallow southern parts. The slope of lake bed in western parts is more than eastern parts.

Figure 1 physiographic schematic Figure of Urmia Lake basin

Figure 2 The morphological units map of study area

2 Materials and methods

The most important components of Urmia lake morphological structure are as follows: the volcanic mountains (Sahand, Islami, Zanbil and Ghahramanloo), Ultramafic acidic rocks in northwest of the lake, Cretaceous and Miocene sedimentary layers in Misho mountains and finally flat mire zones and salt tongues (Figure 2). The morphological structure of coastal land forms surrounding the lake, varies from low slope mud flats in southeast and southern parts to steep cliffed coasts in islands and northwest and western parts. The Urmia lake coasts consist of different sedimentary environments such as: alluvial fans, river deltas, wetlands, salt marshes, and erosive channels. The gained observations from field studies have illustrated that the coastal regions overlook the northwest side of Urmia Lake, from Ghalghachi up to Govarchinghale, are cliffed coasts (Figure 3). The effects of hydrodynamic forces, dissolution of salts and variable water levels of the lake during the past times, have caused erosion and weathering of calcareous sand stone masses, and also improvement of erosive processes, in some parts of watershed, has led to form rocky beaches and erosive bays (Figure 3). The northern beaches structure of Urmia Lake, from Salmas to Tasooj region is red alluvial formation playas which have shaped alluvial terraces in the marginal parts of lake due to runoffs and past floods (Figure 4). The bottom slope of mentioned region is so gentle and fine sandy materials with calcareous pellet particles cover the lake bed (Figure 4). The salt thickness in aforementioned area is inconsiderable. The field studies have proven the dominance of mud flats with playa sedimentation system around Islami Island, also the most part of deposits in current coastal line margins in mentioned region, consist of thick salt sedimentations along with black sludge containing heavy minerals with volcanic origins. Moreover the upper Pleistocene belonged sedimentary terraces have been observed in Gamichi region which is overlooking the southern part of Islami Island (Figure 5). The structural interactions between volcanic masses of Sahand and Urmia lake coastal line along Maragheh – Azarshahr path, have shaped cliffed coasts in eastern and southeast parts of Urmia Lake. The southern parts of Urmia Lake are mostly mud flats yielded from alluvial sedimentation of Zarrinehrood and Siminehrood rivers, and the western sides of lake are narrow coasts with almost steep slopes along with several erosive channels. There are conic volcanic mountains in Ghahramanloo region, which upper Pleistocene sedimentary terraces have been formed at their southern margins (Figure 5). As a result on the base of field studies the most important geological types of Urmia lake coastal areas are as follows: the erosive river sedimentary terraces, the vertical erosional cliffs, the sedimentary terraces produced due to water level fluctuations of Urmia Lake, erosional channels, cliffed and sandy coasts, mud flats and salt marshes. The Urmia lake coastal areas are divided in to several classes in aspect of morphological structure: very low slope and raised mud flats of eastern and southern parts (Islami island – Miandoab), the steep cliffed rocky coasts of northwest (Ghalghachi – GovarchinGhaleh) and southeast (Ajabshir– Maragheh), sandy alluvial beaches in subsiding central north parts (ShahidKalantari causeway), raised zones of central south parts (islands) with detrio clastic, carbonate and salt materials. Also, various sedimentary environments have been shaped at the above morphological units such as: river estuaries (Aji Chai river: the eastern part, Siminehrood and Zarrinehrood rivers: southern parts), wetlands and marginal marshes (containing brackish to fresh water) mostly located in southeast and southwest parts, lake (central part up to northeast), playas (the overlooking coastal to southern region of Ajichai estuary and Tasoojcoastal area) and salt marshes (the Ajichai estuary and western part of Islami island).

Figure 3 The mud flat and erosive terrace with alluvial sediments in coastal parts of Tasooj

Figure 4 the erosion cliffed coasts in northwest of Urmia Lake (Govarchin Ghaleh region)

Figure 5 the sedimentary terrace belonged to upper Pleistocene located in 6 km of Urmia northeast (Ghahramanloo region)

2.2 The morphology of Urmia lake bed

Tarhe No Andishan., 2003, Hydrolic and hydrodynamic study and environment investigation on Urmia lake at the parallel of shahid kalantari High way, Road and transportation ministry of Iran