Environmental Erosion Research

fa بررسی اثر متقابل رودخانه‌ها و تپه‌های ماسه‌ای در مناطق خشک و نیمه‌خشک ایران Investigating the interaction between rivers and sand dunes in arid and semi-arid regions of Iran مدلسازی و تحلیل زمانی و مکانی رخداد انواع مختلف فرسایش محیطی پژوهشي Research فرآیندهای رودخانهای و بادی از عوامل مهم تغییر مورفولوژی در سطح زمین است. هنگامی‌که رودخانه‌ها و تپه‌های ماسهای باهم برخورد می‌کنند، اثر انتقال رسوب بین دو سیستم می‌تواند به تغییر در یک یا هر دو سیستم منجر شود. با توجه به اینکه سطح گستردهای از ایران تحتتأثیر فرسایش بادی و رودخانهای است، بررسی اثر متقابل این دو فرآیند در راستای اهداف مدیریت یکپارچهی سیستمهای رودخانهای و بادی بسیار پر اهمیت است. روش اجرای این تحقیق، توصیفی- تحلیلی است. در این پژوهش برای اولین بار در کشور، 304 سایت که در آنها رودخانه‌ها و تپه‌های ماسه‌ای با هم تلاقی دارند، با استفاده از تصاویر ماهواره‌ای، شناسایی و تجزیه‌ و تحلیل شد. در هر سایت ویژگی‌های کلیدی مانند جهت رودخانه، جهت انتقال ماسه، زاویهی تلاقی رودخانهای - بادی، نوع تپه‌های ماسهای و الگوی کانال رودخانه، مشخص و روابط بین هر یک از عوامل بررسی شد. براساس این داده‌ها، شش نوع مختلف از اثرات متقابل طبقهبندی میشود که تغییرات بین سیستم‌های رودخانه‌ای و بادی را منعکس میکند. نتایج تحقیق نشان داد که بین نوع زاویهی برخورد و نوع تپه ماسهای، زاویهی برخورد و نوع اثر متقابل، و الگوی کانال و نوع اثر متقابل، ارتباط معنی‌داری وجود دارد. این روابط نشان داد که الگوی کانال‌های رودخانه‌ای فعال، بیشترین مکانهایی هستند که سیستمهای رودخانهای یا بادی بر یکدیگر غالب میشوند، اما تعادل بین آنها پایدار نیست. همچنین بین تپههای ماسهای و الگوهای کانال هیچ ارتباطی وجود نداشت. با این وجود، تحقیقات بیشتری در کشور لازم است تا چگونگی تأثیر فرآیندهای رودخانهای و بادی را بر همدیگر و تغییرات ژئومورفولوژیک ناشی از آنها بررسی کند. Extended abstract 1- Introduction Fluvial and aeolian processes are important factors in changing the surface of morphology in the Earth. When rivers and sand dunes meet, the transportation of sediment  between them can lead to one of the systems or both  of them change. With their connection between river sediment and wind systems there would be lots of reactions, but very little has been studied. According to the previous studies in Iran, river and wind systems have been studied separately. Whereas ground-level processes rarely interact with each other, there is so many important proofs that river and wind processes simultaneously are interacting. The interaction between these two processes is important for mantaining the purposes of an intergrated management of fluvial and aeolian systems, considering the wide vastness of Iran’s effect by wind and river erosion. This research is the first inventory of interactions between rivers and sand dunes with the aim of systematically analyzing of the interactions between fluvial and aeolian geomorphology and determining the dominance of Fluvial and aeolian systems in different environments. 2- Methodology The method of this research is descriptive-analytical. This study is a visual search of  the interactions between rivers and sand dunes using satellite imagery hosted by Google Earth (GE) as well as Landsat 8 (USGS) images in the arid and semi-arid regions of Iran. Using these images, surface and landforms from fluvial and aeolian processes can be identified. Because of this reason, this study focuses on the interactions between sand dunes and rivers, where the characteristics of both are easily reconized. To intensify this research, library resources including books and articles have also been used. The search of methodology started at the margins of dryland areas visually identified within Google Earth. Than Identifiable river courses were (bieng  traced up and down the streams to find places where aeolian dunes interact with river courses. Interactions were identified at a regional scale. In this research, 304 sites, where rivers and sand dunes met, are identified and analyzed  by using imagery satellites for the first time in the country. The classification scheme of Liu and Coulthard (2015) has been used to classify the types of interactions between the sand dunes and rivers. At each site a key word   has been used to classify the types of interactions between the sand dunes and rivers. At each site key attributes such as river direction, sand transport direction, fluvial aeolian meeting angle, sand dune type, and river channel pattern were identified and their relationships between each factor was investigated. Based on the data, six different types of interactions between rivers and sand dunes were classified, that reflected changes between the fluvial and aeolian systems. 3- Results According to the data from 304 sites in arid and semi-arid regions of the country, although longitudinal sand dunes are most occurring among all the sand dunes, a similar distribution of channel patterns can be observed for each level . Braided channel patterns have the highest frequency and straight channel patterns and others have the lowest frequency. In all of different channel patterns, the most frequent interaction is fully fluvial dominant and the  lessfrequent  one which is the type of mostly aeolian dominant and balanced. In braided channel patterns, the frequency of interactions from types of mostly aeolian dominant and balanced more than other patterns. In balanced conditions, rivers and dunes connect more in the angles of 45 to 90 degrees 4- Discussion & Conclusions Four variables changes has been analyzed to seek possible relationships between fluvial and aeolian systems, including dune type, channel pattern, meeting angle and the interaction. The results showed that there is a significant relationship between the type of meeting angle and the type of sand dune, the meeting angle and the type of interaction, the channel pattern and type of interaction. These relationships have shown that active river channel patterns are most common where aeolian or fluvial systems are dominated, but the balance between them is not sustainable. There was also no relationship between sand dunes and channel patterns. The results of this study are in line with Liu and Coulthard (2015) studies that show significant relationships between fluvial and aeolian processes. The results of a survey of 304 distributed sites in the arid and semi-arid regions of Iran showed an extensive interaction between rivers and sand dunes. According to the results, it can be said that in many sites, wind and river processes have a significant impact on each other and then on the landforms and geomorphology of the site. Nevertheless, more research is required to investigate how each fluvial and aeolian processes affect each other, as well as geomorphologic changes caused by them in Iran. اثرمتقابل رودخانه‌ای- بادی, تپه ماسه‌ای, رودخانه, ژئومورفولوژی, جهت باد/ رودخانه Fluvial–aeolian interaction, Dunes, River, wind/river direction, Geomorphology 84 103 http://magazine.hormozgan.ac.ir/browse.php?a_code=A-10-586-1&slc_lang=fa&sid=1 Shirin Mohammadkhan شیرین محمدخان mohamadkh@ut.ac.ir 10031947532846005088 10031947532846005088 Yes Assistant Professor of Physical Geography, Faculty of Geography, University of Tehran استادیار گروه جغرافیای طبیعی، دانشکده‌ی جغرافیا، دانشگاه تهران Anvar Moradi انور مرادی Anvar.moradi@ut.ac.ir 10031947532846005089 10031947532846005089 No Ph.D Candidate in Geomorphology, Faculty of Geography, University of Tehran دانشجوی دکتری ژئومورفولوژی، دانشکده‌ی جغرافیا، دانشگاه تهران Fatemeh Moradipour فاطمه مرادی پور Moradipour.f@ut.ac.ir 10031947532846005090 10031947532846005090 No Ph.D Candidate in Geomorphology, Faculty of Geography, University of Tehran دانشجوی دکتری ژئومورفولوژی، دانشکده‌ی جغرافیا، دانشگاه تهران