Analysis of the Wind and Groundwater Roles on Location and Establishment of Internal Graben (Case Study: Sadegh Abad-Bafgh Rig)

Wind erosion is one of the important aspects of land erosion in arid and semi-arid regions. Wind erosion is known as the dominant erosion in these areas and 36 percent of the land surface is arid and semi-arid. Most of these surfaces are almost dry and lack vegetation (Coppinger and et al, 1991). More than 66% of Iran’s area are covered with dry and semi-arid lands, due to lack of moisture and reduced vegetation, there is wind erosion, so that there are about 13 million hectares of land are covered with Sand dunes (Ahmadi, 2001). The accumulation of sand is controlled by various factors, such as the amount of sand, sedimentation rate, wind direction, wind speed and obstacles in the sand movement direction (Moosavi Harami, 2010). Topography is not only known as an effective factor in the formation and density of sand dunes but also indirectly affects the morphology of sand dunes as well as its impact on the climate of the area. In Iran, as a country with a dry climate, due to the dispersion of different sand dunes, various studies conducted in connection with the Ergs establishment. Among these studies, Yamani research (2002) in the area of Kashan Band-Rig and the role of local low-pressure cell in the establishment of this Sandy collection and researches of Maghsoudi, Yamani, Khoshk-Akhlagh and Shahriar (2013) studied the dispersal of four ergs, Khartooran, Chah Jam, Sargardan and Rige –jen in dashte- Kavir Desert.

Daranjir graben is located in the southeast of Yazd Province and extended from Kharanagh to Bafgh. Sadegh Abad Rig inside Dranjir, is located in the 15km northwest of Bafq city. Tectonic properties and position of faults by studying geological maps and studying the status of underground water with field observations and depth of groundwater illustrated the role of underground water in the establishment of Sand dunes. The region's DEM is also used to determine the topographic position and study the role of topography in formation Daranjir Basin. On the other hand, due to the importance of wind in the transfer and density of the Sandy masses, a study of the region's wind regime was carried out using Wrplot and Sand Rose Graph software using Bafq synoptic station, wind rose and Sand rose respectively. Since recognizing the type of morphology of the sand dunes can be a sign of the deposition or displacement of the Sand dunes, it can be seen from the study of the direction of flooding in different periods of time that the dominant morphology of the sand dunes is detected in a field. These studies are about the causes of the wide use of sand mounds Made Also, in order to determine the role of convergence conditions of local winds in Sadegh Abad Bafgh Rig, using the dynamic data of barley in 2016 in IDV 5.0 software, the conditions of convergence of the prevailing surface winds on the construction of the hollow were noted and its effect on the studied peat was investigated. 3.

With regard to the role of wind regime and tectonics in the establishment of sand dunes, it can be said that the results and research findings are about wind and tectonic. The results of study about atmospheric pressure systems, the wind rose and Sand rose drawings show that due to the low-pressure system, the prevailing winds and the transport of sand from different paths are carried out throughout the year. The study of the tectonic conditions of the Darjeer also indicates that these tectonic conditions, have an effect on the groundwater and fault activity and have contributed to the creation of local bays and highlands to the desert in Darjeer. on the other hand, with the ascension of groundwater Adjacent to the earth's surface and increasing the degree of soil moisture, has been effective in stabilizing sand dune and development of Sadeq Abad Bagh Rig. 4.

In this study, the role of dominant wind regime and tectonics in the establishment Rig of Sadegh Abad Bafgh, the tectonic conditions affecting on topographic situation of the flat-hollow daranjir and its adjacent peaks of mountains also affect the wind currents of the region and by creating different temperature conditions in This region has played a significant role in creating the atmospheric pressure patterns of this region and development of various local winds and the flow of sand to the inside of daranjir desert. Another tectonic effect in the region is the activity of faults and their role in the transfer of groundwater near to the Earth's surface and the concentration of sand in the Sadegh abad area. Therefore, it can be said that the tectonic has played a direct and indirect role in concentration sand in the form of the Sadegh Abad Rig. In this way, the activity of faults, the creation of a difference in the topography and obstacle in the path of the sand direction in the adjacent Bafgh fault has directly played a role in the concentration and deposition of sand grains. Also, tectonics which has an effect on the development of groundwater transfer to the adjacent to the earth's surface, has increased of soil moisture in the adjacent Bafq fault, also local winds move the sand to the Daranjir center so it has affected the development of Sand dune in this part of daranjir Desert.