چکیده:
تپههای ماسهای بهمثابة یکی از لندفرمهای مناطق بیابانی ایران وسعت زیادی از بخشهای این مناطق را دربرگرفته است. شناخت موقعیت، رفتار و ماهیت تپههای ماسهای و شناسایی محلهای برداشت، حمل و رسوبگذاری این لندفرمها به دلیل مشکلات عدیدهای که برای محیط زیست انسانی داشته، ضروری است. در این پژوهش مطالعة الگوی گسترش و توسعة تپههای ماسهای در سطح ریگ زهک در شرق دشت سیستان در دو بخش انجام شده است؛ در بخش اول بهمنظور بررسی تغییرات محدودة تپههای ماسهای از دو تصویر ماهوارهای سری LandSat-7 مربوط به سال 2001 (ETM) و Landsat 8 مربوط به سال 2019 و برای بررسی روند تغییرات و جابهجاییها از تصاویر گوگلارث منطقه مربوط به سالهای اخیر (2006، 2018) استفاده شد؛ در بخش دوم برای آگاهی از وضعیت بادهای فعال و الگوی حرکت آنها، دادههای ایستگاه بادسنجی ارزیابی شد. نتیجة بررسی تپهها در بخشهای مختلف سطح ریگ نشاندهندة جابهجایی با روند شمال غربی- جنوب شرقی است. این نتیجه با نتایج تحلیل دادههای جهت الگوی باد همخوانی و مطابقت داشته است؛ اما میانگین مقدار جابهجایی 53/1 متر در سال برای بازة زمانی 12ساله (2006 تا 2018) با نتایج دادههای ایستگاه بادسنجی زابل که مقدار حمل ماسه را بیش از 300 تن در متر برای یک سال نشان میدهد و بررسی روند تغییرات سرعت باد در این ایستگاه همخوانی نداشته است. این موضوع نشاندهندة این واقعیت است که حداکثر این مقدار حاصلشده به پیش از تثبیت تپههای ماسههای فعال مربوط بوده است؛ علاوه بر این ماسههای روان در سطح زمین و مستقل از تپههای ماسهای حرکت میکنند که با تصاویر قابل اندازهگیری نیستند.
Introduction Aeolian sand transport is a complex process influenced by many variables including wind conditions (Lancaster, 1985; Anderson & Haff, 1988; Gillette et al., 2001; Zou et al., 2001; Liu et al., 2005), grain size and sand surface moisture (Jackson, 1998; Wiggs et al., 2004), surface crusting (Leys & Eldridge, 1991), topography (Iversen & Rasmussen 1994; Hesp et al., 2005), and vegetation cover (Buckley, 1987; Kuriyama et al., 2005). The importance of sand dunes studies is due to their impacts on water and soil resources, flora and fauna, human infrastructure, and roads. Sand drifting can lead to losing agricultural lands, burying residential buildings, railways, highways, and other infrastructures in many areas of the desert (Zhu et al., 1980; Lei et al., 2003; Dong, 2004). Bagnlod (1981) has done the first study on the movement of sand dunes. In recent years, many studies have been done on the cognition of sand dune processes, which include the study of the winds and sands migration in different dunes. Needless to say that significant signs of progress have been obtained. In this regard, there is no doubt that the remote sensing technique and its capabilities, as well as the optimal time sequence of satellite imagery in mapping erg areas, have fundamental performances. Using these images, a substantial area of sand dunes can be examined in a short period of time, and then we can talk about the identification of active dunes, their expansion, and relocation. Methodology To study the changes and migration of sand dunes, this study was conducted in two stages. At the first stage, to evaluate changes in the range of sand dunes in the study area, Landsat images were used for the years 2001 and 2019. Moreover, to detect the changes in the Zahak Erg range the ENVI software was used. The results of this section can be important in the overall assessment of the area. Additionally, in order to detect the trend of changes in those parts where significant shifting occurred, we used either Landsat or the Google Earth images with different time intervals. It worth mentioning that for geo-referencing the Google Earth images of recent years (2006-2018) the Stitch Map Software was used. Moreover, to draw the sand rose, the Sand Rose software was used. Sand rose is the Graph of Portable sand by wind energy, which was used by Fryberger and Dean (1979) for the first time. In order to draw this Graph, winds that were faster than the erosion velocity threshold were developed into vector units as sand drift potential. Discussion Mobility is the most important characteristic of sand dunes. In this regard, special attention should be paid to the importance of wind in changing the sand dunes morphology. In addition, studies of sand dunes migration provide basic knowledge about wind processes and sand transfer values. In this study, monitoring and detection of the sand dunes relocation rate have been considered based on the use of Landsat images (for the years 2001-2019). At the first stage, the regions that have been faced changes were identified using the change detection technique for the entire range of Erg. Based on the output map, marked areas with the red color experienced the maximum changes, and also, in this section, sand dunes have been more developed. The differences between the two images within the sand dunes area were estimated at about 23 km2. However, the pattern of sand dunes migration represents relocation from the Northwest to the Southeast. At the next stage of the study, to understand the change rate and relocation trend, Google Earth images were used (years 2006 and 2018). Furthermore, the region with significant changes has been selected for a closer look. Moreover, using Stitch Map software, the georeferenced images were extracted. It worth mentioning that, from the five selected zones on the Erg surface, a total of 368 cases of sand dunes were quantitatively analyzed. According to the results, the greatest amount of migration was found for zone 3 with the amount of 24.72 m, in contrast, the lowest value was calculated at about 14.16 m for zone 5. In addition, the migration average rate for a period of 12 years was calculated. Here, the maximum migration belonged to zone 3 which is 2.06 meters per year. While the minimum one allocated to zone 5 was 1.18 meters per year. Conclusion In this study, the authors monitored changes in sand dunes using satellite imagery data and wind data of meteorological stations of Zahak Erg. In this regard, the sand dunes activity rate, dunes migration pattern, and also factors affecting their intensity and patterns were identified. The results of the 368 studied sand dunes in different parts of the erg surface indicated displacement with a northwest-southeast trend, which is consistent with the results of data analysis for wind pattern. But the average amount of displacement of 1.53 meters per year for a period of 12 years (2006 to 2018) with the results of data from Zabol wind station showed the amount of sand carrying more than 300 tons per meter for a year. The changes in wind speed at this station were inconsistent and it was shown that the maximum value obtained was before the stabilization of the active sand dunes. In addition, smooth sands move on the surface of the earth, independent of sand dunes, which cannot be measured by images. Keywords: Sand Dunes, Remote Sensing, Wind Data, Wind erosion, Zahak Erg. References: - Ahmadi, H. (2006). Applied Geomorphology Volume 2 Desert- Wind Erosion. Tehran: University of Tehran Press. - Ahmadian, M. A. (2008). Desert (A Systematic Approach to the Desertification and Desertification Process). Geographical Research Quarterly, 2(53), 146-159. - Al-Awadhi, J. M., Al-Helal, A., & Al-Enezi, A. (2005). Sand Drift Potential in the Desert of Kuwait. Journal of Arid Environments, 63, 425–438. - Bagnold, R. A. (1941). The Physics of Blown Sand and Desert Dunes. London: Chapman and Hall, pp. 104–106. - Baitis, E., Kocurek, G., Smith, V., Mohrig, D., Ewing, R. C., & Peyret, A. P. B. (2014). Definition and Origin of the Dune-Field Pattern at White Sands, New Mexico. Aeolian Research, 15, 269–287. - Delgado-Fernandez, I., & Davidson-Arnott, R. (2011). Meso-Scale Aeolian Sediment Input to Coastal Dunes: The Nature of Aeolian Transport Events. Geomorphology, 126(1-2), 217-232. - Dong, Z., Wang, T., & Wang, X. (2004). Geomorphology of the Megadunes in the Badain Jaran Desert. Geomorphology, 60(1-2), 191-203. - Ebrahimzadeh, I. (2018). A Regional Analysis of Urban-Rural Relationships in Sistan. PhD Thesis in Geography and Urban-Regional Planning, Faculty of Literature and Humanities, University of Isfahan, pp. 85-65. - Fryberger, S. G., AL‐Sari, A. M., Clisham, T. J., Rizvi, S. A., & ALHinai, K. G. (1984). Wind Sedimentation in the Jafurah Sand Sea, Saudi Arabia. Sedimentology, 31(3), 413-431. - Fryberger, S. G., & Dean, G. (1979). Dune Forms and Wind Regime. USA: Geological Survey Professional Paper 1052–F, pp. 137–169. - Gillies, J. A., & Lancaster, N. (2013). Large Roughness Element Effects on Sand Transport, Oceano Dunes, California. Earth Surface Processes and Landforms, 38(8), 785-792. - Hamdan, M. A., Refaat, A. A., & Wahed, M. A. (2016). Morphologic Characteristics and Migration Rate Assessment of Barchan Dunes in the Southeastern Western Desert of Egypt. Journal of Geomorphology, 257, 57-74. - Hereher, M. E. (2018). Geomorphology and Drift Potential of Major Aeolian Sand Deposits in Egypt. Journal of Geomorphology, 304, 113-120. - Hermas, E., Leprince, S., & Abou El-Magd, I. (2012). Retrieving Sand Dune Movements Using Sub-Pixel Correlation of Multi-Temporal Optical Remote Sensing Imagery, Northwest Sinai Peninsula, Egypt. Journal of Remote Sensing of Environment, 121, 51-60. - Hesp, P. A., Davidson-Arnott, R., Walker, I. J., & Ollerhead, J. (2005). Flow Dynamics Over a Foredune at Prince Edward Island, Canada. Journal of Geomorphology, 65(1-2), 71-84. - Housing Foundation of the Islamic Revolution of Sistan and Baluchestan Province. (2019). Technical Unit and Rural Development Studies. - Khosravi, M. (2005). Research Project of Ecological and Environmental Effects of 120-Day Winds in Sistan. Environmental Protection Organization of Sistan and Baluchestan Province, Consultant of Sistan and Baluchestan Institute of Earth Sciences and Geography, p.300. - Kuriyama, Y., Mochizuki, N., & Nalashima, T. (2005). Influence of Vegetation on Aeolian Sand Transport Rate from a Backshore to a Foreshore at Hasaki, Japan. Journal of Sedimentology, 52(5), 1123–1132. - Lancaster, N., Nickling, W. G., & Gillies, J. A. (2010). Sand Transport by Wind on Complex Surfaces: Field Studies in the McMurdo Dry Valleys, Antarctica. Journal of Geophysical Research: Earth Surface, 115(3). - Latifi, L. (2006). Investigating the Progress of Sand Dunes Using Satellite Images in Recent Droughts in the North and East of Sistan Plain. Master Thesis, Department of Geography, Islamic Azad University, Mashhad Branch. - Liu, L.Y., Skidmore, E., Hasi, E., Wagner, L., & Tatarko, J. (2005). Dune Sand Transport as Influenced by Wind Directions, Speed and Frequencies in the Ordos Plateau, China. Journal of Geomorphology, 67(3-4), 283–297. - Maghsoudi, M., Mohammadi, M., Khanbabaei, Z., Mahboubi, S., Baharvand, M., & Hajizadeh, A. H. (2017). Monitoring the Movement of Erg and Barkhans in the West of Lut (Peshouieh). Journal of Quantitative Geomorphological Research, 5(4), 189-176. - Maghsoudi, M., Navidfar, A., & Mohammadi, A. (2017). The Sand Dunes Migration Patterns in Mesr Erg Region Using Satellite Imagery Analysis and Wind Data. Journal of Natural Environment Change, 3(1), 33-43. - Mohamed, I. N., & Verstraeten, G. (2012). Analyzing Dune Dynamics at the Dune-Field Scale Based on Multi-Temporal Analysis of Landsat-TM Images. Journal of Remote Sensing of Environment, 119, 105-117. - Negaresh, H., & Latifi, L. (2008). Geomorphological Analysis of the Progress of Sand Dunes East of the Sistan Plain in Recent Droughts. Journal of Geography and Development, 6(12), 60-43. - Noroozhi, F. (1993). Investigating the Destructive Effects of Helmand River Floods. MA Thesis, Department of Geography, Sistan and Baluchestan University, p.195. - Piri, H., Abbaszadeh, M., Rahdari, V., & Maleki Najafabadi, S. (2013). Comparative Assessment of 4 Meteorological Drought Indices Using Cluster Analysis Method (Case Study of Sistan and Baluchestan Province). Journal of Water Resources Engineering, 6(17), 25-36. - Pye, K., & Tsoar, H. (2009). Aeolian Sand and Sand Dunes. Berlin: Springer-Verlag. - Salighe, M. (2003). Attention to the Wind in the Construction of the Physical Body of Zabol. Journal of Geography and Development, 1(2), 109-121. - Sargzi, H. (2005). Origin and Assessment of Severity and Damage of Sand Dunes in Niatak Sistan Desert. Master Thesis, Gorgan University of Natural Resources, p.136. - Sherman, D. J., & Li, B. (2012). Predicting Aeolian Sand Transport Rates: A Reevaluation of Models. Journal of Aeolian Research, 3(4), 371-378. - Sparavigna, A. C. (2013). A Study of Moving Sand Dunes by Means of Satellite Images. International Journal of Sciences, 2. - Tsoar, H. (2005). Sand Dunes Mobility and Stability in Relation to Climate. Physica A: Statistical Mechanics and its Applications, 357(1), 50-56. - Wang, X., Eerdun, H., Zhou, Z., & Liu, X. (2007). Significance of Variations in the Wind Energy Environment over the Past 50 Years with Respect to Dune Activity and Desertification in Arid and Semiarid Northern China. Journal of Geomorphology, 86(3-4), 252-266. - Wiggs, G. F. S., Atherton, R. J., & Baird, A. J. (2004). Thresholds of Aeolian Sand Transport: Establishing Suitable Values. Journal of Sedimentology, 51(1), 95-108. - Yao, Z. Y., Wang, T., Han, Z. W., Zhang, W. M., & Zhao, A. G. (2007). Migration of Sand Dunes on the Northern Alxa Plateau, Inner Mongolia, China. Journal of Arid Environments, 70(1), 80-93. - Yurk, B. P., Hansen, E. C., & Hazle, D. (2013). A Deadtime Model for the Calibration of Impact Sensors with an Application to a Modified Miniphone Sensor. Journal of Aeolian Research, 11, 43-54. - Zhang, G., Azorin-Molina, C., Shi, P., Lin, D., Guijarro, J. A., Kong, F., & Chen, D. (2019). Impact of Near-Surface Wind Speed Variability on Wind Erosion in the Eastern Agro-Pastoral Transitional Zone of Northern China, 1982–2016. Agricultural and Forest Meteorology, 271, 102-115. - Zhang, Z., Dong, Z., & Li, C. (2015). Wind Regime and Sand Transport in China’s Badain Jaran Desert. Journal of Aeolian Research, 17, 1-13.
خلاصه ماشینی:
پايش تغييرات تپه هاي ماسه اي با تحليل تصاوير ماهواره اي و داده هاي ايستگاه بادسنجي نمونۀ پژوهش : محدودٔە ريگ زهک در شرق دشت سيستان فاطمه گراوند، دانشجوي دکتري گروه جغرافياي طبيعي، دانشکده جغرافيا، دانشگاه تهران ، تهران ، ايران f_geravand@ut.
در اين پـژوهش مطالعـۀ الگـوي گسـترش و توسـعۀ تپه هاي ماسه اي در سطح ريگ زهک در شرق دشت سيستان در دو بخش انجام شده است ؛ در بخـش اول بـه منظـور بررسـي تغييرات محدودٔە تپه هاي ماسه اي از دو تصوير ماهواره اي سري ٧-LandSat مربوط به سـال ٢٠٠١ (ETM) و Landsat ٨ مربوط به سال ٢٠١٩ و براي بررسي روند تغييرات و جابه جاييها از تصاوير گوگل ارث منطقه مربوط بـه سـال هـاي اخيـر (٢٠٠٦، ٢٠١٨) استفاده شد؛ در بخش دوم براي آگاهي از وضعيت بادهاي فعـال و الگـوي حرکـت آنهـا، داده هـاي ايسـتگاه بادسنجي ارزيابي شد.
اين نتيجه با نتايج تحليل داده هاي جهت الگوي باد همخواني و مطابقت داشته است ؛ امـا ميـانگين مقـدار جابه جايي ١/٥٣ متر در سال براي بازٔە زماني ١٢ساله (٢٠٠٦ تا ٢٠١٨) با نتايج داده هاي ايسـتگاه بادسـنجي زابـل کـه مقـدار حمل ماسه را بيش از ٣٠٠ تن در متر براي يک سال نشان مي دهـد و بررسـي رونـد تغييـرات سـرعت بـاد در ايـن ايسـتگاه همخواني نداشته است .
Location of Zahak sand area in Sistan and Iran plain (Authors, 2019) روش شناسي پژوهش به منظور بررسي تغييرات و جابه جايي تپه هاي ماسه اي ، اين مطالعه در دو سطح انجـام شـده اسـت .