انجمن ایرانی ژئومورفولوژی پژوهشهای ژئومورفولوژی کمّی 22519424 14 2 2025 09 23 Geomorphometric Characterization of Dunes in the Rig-e-Yalan, Dasht-e-Lut: Aeolian Processes and Spatial Analysis ویژگی‌های ژئومورفومتریک تلماسه‌ها در ریگ یلان، دشت لوت: فرآیندهای بادی و تحلیل مکانی 24 41 224007 10.22034/gmpj.2025.510974.1551 FA ابوالقاسم گورابی گروه جغرافیای طبیعی، دانشکده جغرافیا دانشگاه تهران، تهران، ایران. 0000-0002-2787-8687 Journal Article 2025 03 06 1. Introduction The morphology of dunes stands as a pivotal marker of aeolian processes and wind regimes in hyper-arid environments. Detailed geomorphometric analysis of dunes offers critical insights into sediment transport dynamics, wind-driven geomorphological processes, and the protracted evolution of desert landscapes. The Lut Desert (Dasht-e Lut) in eastern Iran ranks among the most hyper-arid regions globally, characterized by extreme temperatures, low relative humidity, and elevated aeolian activity. Within its eastern sector, the Rig-e Yalan sand sea showcases an extensive suite of megadune morphologies, including longitudinal (seif) and barchan forms, which have developed under the influence of prevailing and persistent wind regimes. Although this region holds substantial promise for advancing research into aeolian geomorphology, comprehensive morphometric studies leveraging remote sensing techniques remain notably limited. Further geomorphological investigation into the Rig-e Yalan sand sea could significantly enhance understanding of the interplay between prevailing wind conditions and dune morphology formation processes in hyper-arid settings. To date, the deployment of remote sensing and geospatial methodologies, such as geomorphometry, has been insufficiently explored in this context. This study aims to conduct a rigorous geomorphometric assessment of dunes within the Rig-e Yalan sand sea, employing Digital Elevation Models (DEM) and geospatial analysis techniques. The research is designed to identify the dominant wind direction, quantify dune geomorphometric characteristics, and analyze their linkage to aeolian sediment transport processes in this hyper-arid landscape. 2. Methodology This investigation integrates remote sensing, Google Earth Engine (GEE), and Geographic Information Systems (GIS)-based morphometric analysis to examine the aeolian geomorphology of the Rig-e Yalan dune field. The methodological framework encompasses data acquisition, preprocessing, geomorphometric analysis, and interpretation, structured as follows: (1) Data Acquisition: The core dataset comprises the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) with a 30-meter resolution, sourced from the United States Geological Survey (USGS). To corroborate dune morphology patterns and aeolian sediment transport, supplementary multispectral imagery from Landsat and Sentinel-2 satellites was incorporated. These datasets provide a robust foundation for analyzing topographic and surface reflectance variations across the hyper-arid landscape. (2) Preprocessing: The SRTM DEM underwent processing within Google Earth Engine (GEE) and ArcGIS platforms. To refine data quality, a Gaussian kernel filter (radius 15, sigma 2) was applied, mitigating noise while retaining critical geomorphic signatures such as dune crests and interdune troughs. The study area perimeter was demarcated using a fusion of optical and radar-based satellite imagery, ensuring accurate delineation of the Rig-e Yalan dune field amidst its complex aeolian terrain. (3) Geomorphometric Analysis: A suite of geomorphometric parameters was calculated to characterize the dune field’s morphology and its interaction with wind regimes, including: • Slope (S): Quantifies the inclination of dune surfaces, a primary control on aeolian sediment entrainment. These indices were derived through advanced spatial analysis tools within GIS, with their spatial variability mapped to elucidate geomorphological patterns across the Rig-e Yalan dune field. Statistical correlation analyses were subsequently conducted to explore the interdependencies between these geomorphometric attributes and wind-induced sediment transport dynamics, enhancing understanding of aeolian process-form relationships in this hyper-arid environment. 3. Results and Discussion The findings reveal distinct geomorphometric patterns linked to aeolian processes in Rig-e Yalan: 3.1 Dominant Wind Directions: Analysis of dune orientations and sediment transport indices suggests that the prevailing wind direction is from the southeast (SE) towards the northwest (NW). This is indicated by steeper lee slopes in the NW direction and windward slopes in the SE, confirming sediment transport trends. 3.2 Dune Morphometry and Spatial Patterns: - The average slope of dunes is highest in the NW region (10.79°) and lowest in the SE (7.20°), suggesting that NW dunes experience higher sediment accumulation while SE dunes undergo more wind erosion - Surface roughness values exhibit significant variation, with the highest values in NW dunes (12.83) and lower values in SE dunes (8.64), supporting the hypothesis that NW serves as a sediment deposition zone. - STI values reinforce these patterns, as NW dunes show significantly higher sediment retention (STI = 146.14), whereas SE dunes have lower STI (60.61), indicating active erosion in the SE sector. 3.3 Wind-Erosion and Sediment Deposition: The correlation between slope and surface roughness (r = 0.9325) highlights the role of wind strength in shaping dune morphology. The relationship between sediment transport index and elevation variations suggests that dunes act as dynamic sediment traps, influenced by seasonal wind fluctuations. 3.4 Influence of Secondary Winds: While SE-NW is the dominant wind corridor, secondary wind interactions from the north (N) and northeast (NE) contribute to complex dune reorganization, creating asymmetrical ridge alignments. These secondary winds lead to partial redistribution of sediments in specific sub-regions, modifying local dune morphology. The morphometric patterns observed in this study align with previous global studies on aeolian environments, such as the Namib and Thar deserts. However, the unique geomorphic setting of Rig-e Yalan, with extreme climatic conditions and complex wind interactions, presents new insights into dune evolution in hyper-arid environments. 4. Conclusion This study investigated the geomorphometric characteristics of dunes in the Rig-e Yalan sand sea, Lut Desert, to identify the dominant wind direction using SRTM digital elevation models and advanced analyses in Google Earth Engine and GIS. Findings revealed that the primary wind direction from southeast to northwest (SE-NW) shapes dune morphology, with erosion in SE slopes (mean slope 7.20°, STI=60.61) and sediment accumulation in NW (mean slope 10.79°, STI=146.14). Geomorphometric indices, particularly STI and RPI, accurately predicted wind direction by analyzing slope, surface roughness (NW: 12.83, SE: 8.64), and curvature patterns. Secondary winds (NE-SW and N-S) influence dune morphology in northeastern and southwestern sectors, respectively. Comparisons with global studies (Namib, Thar, Lut) confirmed the findings and highlighted innovations in multi-directional wind analysis and comparative morphometric matrices. However, the 30-meter resolution of SRTM data and the absence of field-based wind measurements limited the precision of fine-scale analyses. These results enhance understanding of aeolian processes and support sustainable land management, wind erosion control, and environmental planning in arid regions. Future research should integrate field wind data, multi-temporal remote sensing, and CFD modeling to refine dune dynamics models. این پژوهش به بررسی ارتباط ویژگی‌های مورفومتریک تلماسه‌ها و الگوهای بادی در ریگ یلان ، واقع در غرب دشت لوت، ایران، با استفاده از داده‌های مدل ارتفاعی رقومی پرداخته‌است. هدف اصلی این پژوهش، شناسایی جهات باد غالب و فرعی با تأکید بر ویژگی‌های ژئومورفیک تلماسه‌ها است. روابط بین شاخص‌های ژئومورفیک تلماسه‌ها و جهت‌گیری بادهای غالب با مطالعه و تحلیل آماری فضایی داده‌های مورفومتریک (شیب، زبری سطح، انحنای پروفیل، انحنای طرح، شاخص موقعیت توپوگرافی، شاخص موقعیت نسبی، تفاوت ارتفاع، و شاخص حمل رسوب تعین شده‌اند. در این راستا با بهره‌گیری از Google Earth Engine و GIS، شاخص‌های مورفومتریک از داده‌های SRTM محاسبه و با فیلتر کرنل گاوسی (شعاع 15، سیگما 2) نویزها کاهش یافتند. ارزیابی تأثیرات متقابل این شاخص‌ها نشان داد که تغییرات انحنای پروفیل و پلان تلماسه‌ها می‌تواند به‌عنوان شاخصی برای شناسایی مناطق فرسایش‌پذیر در نظر گرفته شود. یافته‌های کلیدی نشان‌دهنده جهت باد غالب از جنوب شرقی و جنوب (SE,S)، با ستیغ‌های تلماسه‌ای در راستای شمال غربی و شمال (NW,N)، و شاخص تقارن 0.21- با سطح اطمینان بالا (۹۵٪) هستند. نتایج تحلیل‌ها (میانگین شیب 11.87 درجه در NW، زبری 13.90 در NW، و STI =162.70 در NW در NW) الگوهای ستیغ‌ها و گودال‌ها را در جهت‌های NW و SE تأیید کردند. نتایج همچنین نشان دادند که تغییرات شاخص حمل رسوب در امتداد محور NW-SE همبستگی بالایی با تغییرات زبری سطح دارد، که می‌تواند در مدل‌سازی پویایی تلماسه‌ها کمک کنند. نتایج همچنین بیانگر پتانسیل بالای داده‌های دورسنجی برای پایش تغییرات مورفولوژیکی در مناطق فراخشک و جایگزین مناسبی برای داده‌های میدانی در مناطقی که دسترسی به داده‌های بادشناسی محدود و ممکن نیست، است. این نتایج اهمیت تحلیل مورفومتریک مشتق‌شده از DEMs را برای درک فرآیندهای بادی در بیابان‌ها، مدیریت منابع طبیعی، و پیش‌بینی فرسایش بادی برجسته می‌کنند. محدودیت‌هایی مانند فقدان داده‌های میدانی و بادی محلی، مسیرهای تحقیقاتی آینده را مشخص می‌کنند.

https://www.geomorphologyjournal.ir/article_224007_28dce2a63ff98d7c991e10b658b86327.pdf