عنوان مقاله [English]
Wind erosion is one of the most 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 devoid of vegetation. More than 66% of Iran is covered with arid 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 covered with sand dunes. The accumulation of sand is controlled by various factors including the amount of sand, sedimentation rate, wind direction, wind speed and obstacles in the sand movement direction. 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 their impacts on the climate of the area. In Iran, as a country with arid climate, due to the dispersion of different sand dunes, various studies were conducted about the Ergs. Among these studies, researches by Yamani (2002) in the area of Kashan Band-Rig and the role of local low-pressure cell in the establishment of this sandy collection is considerable for understanding the sand development. The researches of Maghsoudi, Yamani, Khoshk-Akhlagh and Shahriar (2013) examined the dispersal of four ergs of Khartooran, Chah Jam, Sargardan and Rige–jen in Dashte- Kavir Desert.
Materials and Methods
In the southeast of Yazd Province, there is Daranjir graben extended from Kharanagh to Bafgh. Sadegh Abad Rig inside Dranjir is located in the 15 km northwest of Bafgh City. Studying tectonic properties and position of faults by geological maps and studying the underground water with field observations and depth of groundwater illustrated the role of underground water in the establishment of the 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 on wind regime of the region based on Bafgh synoptic stations data was carried out using Wrplot and Sand Rose Graph software. Since recognizing the morphology of the sand dunes can be a sign of the deposition or displacement of the landforms, 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 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. Convergence of the prevailing surface winds on the construction of the hollow and its effects on the study case were investigated using the synoptic data.
Results and discussion
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 activities. The results of the study about atmospheric pressure systems, the wind rose and sand rose 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 influence on the groundwater and fault activity and have contributed to the creation of local bays and highlands in the desert in Darjeer. On the other hand, the ascension of groundwater adjacent to the earth's surface and increase in the degree of soil moisture has been effective in stabilizing sand dune and development of Sadeq Abad Bagh Rig.
In this study, the role of dominant wind regime and tectonics on the establishment of Sadegh Abad Bafgh have been examined to understand the effects of tectonic conditions on topographic situation of the flat-hollow Daranjir and its adjacent peaks of mountains. The wind currents of the region created different temperature conditions. 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 inside the 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, 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 of sand in the configuration of the Sadegh Abad Rig. In this way, the activity of faults in creation of a difference in the topography in the path of the sand movement in the adjacent Bafgh fault has directly played a role in the concentration and deposition of the sand grains. The tectonics has an effect on the development of groundwater transfer to the adjacent areas. It has increased soil moisture in the adjacent Bafq fault; also the local winds move the sand to the Daranjir and affected the development of sand dune in this part of Daranjir Desert.