| چکیده انگلیسی مقاله |
Abstract
Sand dunes are prominent features of desert regions and are widely distributed across Iran. Despite their significant environmental impacts and importance in various planning processes, comprehensive studies on Iran's sand dunes have been lacking. This study aimed to evaluate the morphometric and morphodynamic characteristics of Iran's sand dunes. Google Earth and Landsat 8 images were utilized as the primary research data, while the key analytical tools employed were Google Earth and ArcGIS. Initially, the study delineated the areas of all sand dunes in Iran, categorizing them into 9 classes based on their geographical locations. Using Google Earth images and data from 791 sample points, the movements of the sand dunes were assessed from 2005 to 2020. The findings revealed that the total area of Iran's ergs was 47,811 km2, accounting for approximately 2.9% of the country's total area. Notably, Lut Sand Dune covering 14,629 km2, the sand dunes surrounding the desert plain of Chaleh-Mesileh with 13,081 km2, and the eastern sand dunes with 5,737 km2 represented the largest sand dune formations in Iran. Furthermore, the morphodynamic assessment indicated that the highest movement rates exceeding 90 m occurred in the southern regions of the main Lut sand dunes, Sistan sand dunes, and Shotori ergs. In contrast, specific areas, such as the isolated sand dunes of Khuzestan, exhibited minimal movement—approximately 2 m—due to stabilization efforts by vegetation from 2005 to 2020.
Keywords: Sandstone Morphometry, Sandstone Morphodynamics, Iranian Sandstones.
Introduction
Morphology of sand dunes is influenced by various factors, including topography, wind speed, and wind direction. Given that the speed and direction of winds in a region can vary significantly across different seasons and due to diverse topographic influences, the morphology of sand dunes is also highly variable. Additionally, sand dunes exhibit active dynamics that can pose various hazards, such as encroaching on human settlements and creating dust centers, making their study crucial. Research on the geographical distribution of sand dunes worldwide has shown that a substantial portion is found in the subtropical high-pressure belt. As Iran is situated within the dry and desert belt of the world, sand dunes are both widespread and extensive throughout the country. Moreover, significant cities are located near these sand dunes, emphasizing the importance of understanding the natural factors at play, particularly the role of wind in sand transport. Despite the extensive presence of sand dunes in Iran, comprehensive studies on them are lacking. The existing research has primarily been case-specific with no thorough scientific investigations conducted, resulting in many of Iran's sand dunes remaining poorly understood or unknown. Given these issues, it is essential to identify and monitor Iran's sand dunes, provide a general classification, and evaluate their morphometric and morphodynamic characteristics. This research aimed to address these important aspects.
Materials and Methods
This study employed remote sensing methods, utilizing Google Earth and Landsat 8 images as the primary sources of research data. The key tools used were Google Earth and ArcGIS, the first of which facilitated mapping the areas of sand dunes and monitoring their movements, and the second was employed to create the necessary maps. Additionally, the Inverse Distance Weighting (IDW) interpolation method was utilized to generate a map illustrating sand dune movements. The study was conducted in 3 general stages aligned with its objectives. In the 1st stage, the information about the locations of sand dunes in Iran was gathered through library research. Subsequently, the precise locations of these dunes were mapped using Google Earth images and a manual digital method. In the 2nd stage, the mapped sand dunes were categorized into 9 classes based on their geographic locations. Following this classification, the total areas of each dune and its subcategories were calculated. In the 3rd stage, the status of sand dune movements from 2005 to 2020 was assessed using Google Earth images and the data from 791 sample points.
Research Findings
The findings indicated that the total area of Iran's sand dunes was 47,811 km2, accounting for approximately 2.9% of the country's total area. Among these, Lut Erg covering 14,629 km2 stood out as the largest, which constituted 30.6% of the total area of sand dunes in Iran. Following Lut Erg, the southern Alborz-Kavir Plain and the eastern sand dunes were the next largest with areas of 13,081 km2 (27.4%) and 5,737 km2 (12%), respectively. Monitoring the movements of sand dunes using 791 sampling points revealed significant movements between 2005 and 2020. In certain areas, particularly in the southern regions of the main Lut sandbank, sand dunes had shifted by approximately 100 m. Additionally, Sistan and Baluchestan Erg and Shottri Erg exhibited considerable movements during this period. Conversely, in regions, such as the isolated erg of Khuzestan, the movements of sand dunes was minimal—about 2 m—due to stabilization from vegetation cover between 2005 and 2020.
Discussion of Results & Conclusion
The findings of this study demonstrated that sand dunes were significantly distributed across Iran, covering extensive areas of the country's desert and coastal regions. This geographical diversity had led to the assignment of different names to sand dunes in various regions. Due to their wide variety and the absence of a comprehensive classification system, this study categorized Iran's sand dunes into 9 distinct classes based on their locations. The results indicated that the total area of sand dunes in Iran was 47,811 km2, representing approximately 2.9% of the country's total area. Notably, Lut Riq was identified as the largest sand dune formation, encompassing 30.6% of the total sand dune area in Iran. Furthermore, assessment of the morphodynamic status of these sand dunes revealed that in some regions, the rate of movement between 2005 and 2020 exceeded 90 m. Overall, this study highlighted the extensive nature of Iran's sand dunes, many of which exhibited active dynamics. Given that a significant portion of these sand dunes is located near populated areas, it is crucial to implement measures to prevent their encroachment on human settlements. Establishing vegetation cover as successfully done in certain areas of Khuzestan is one effective strategy to mitigate this issue. |