ارتباط كمّي ويژگي‎هاي مورفولوژيك حوضه‌هاي زهكشي و مخروط‌افكنه‌هاي آنها در ايران مركزي

Quantity Relationships between Characteristics of Drainage Basin and Theirs Alluvial Fan in Central Iran

تحليل روابط بين ويژگي‌هاي مورفومتري حوضه‎ي زهكشي ـ مخروط‌افكنه از موضوعات اساسي هيدروژيومورفولوژيكي است كه اين پژوهش بدان پرداخته است. براي استخراج مرز و 21 عامل مورفولوژيك از 30 حوضه و مخروط‌افكنه در قلمرو ايران مركزي، از داده‌هاي رقومي ارتفاعي و نرم‌افزار WMS 8.4استفاده شده است. تدقيق مرز حوضه‌ها و مخروط‌افكنه‌ها استخراجي با همپوشاني آنها بر روي تصاوير مختلف انجام شد. تحليل آماري در محيط نرم‌افزارهاي آماري انجام گرفته است. ارتباط بين شاخص‌هاي ژيومورفيك حوضه ـ مخروط‌افكنه به دو گروه پارامترهاي وابسته و غير وابسته تقسيم مي‌شوند. نتايج نشان مي‌دهند كه الگوي كلّي همبستگي بين پارامترهاي بيست‎ويك‎گانه فوق در ايران مركزي با الگوي كلّي نواحي ديگر يكسان است. ميزان همبستگي بين پارامترهاي وابسته با كاهش قلمرو پژوهش از سطح ناحيه‎ي ايران مركزي به سطح مناطق كوچك‌تر افزايش يافته و با مقياس بررسي، ارتباط تنگاتنگي دارند. سطح همبستگي بين پارامترهاي ژيومورفيك حوضه ـ مخروط‌افكنه از گروه‌هايي با مساحت زياد به گروه‌هايي با مساحت كمتر، افزايش مي‌يابد. در بين پارامترهاي مورد بررسي، همبستگي و ارتباط بين مساحت، شيب و طول حوضه‌هاي زهكشي ـ مخروط‌افكنه‌ها، به صورت زوج‌هاي مختلف (6 رابطه) نسبت به پارامترهاي ديگر ژيومورفيك بيشتر است. همبستگي بين پارامترهاي حوضه ـ مخروط‌افكنه در مناطقِ كمابيش همگون هيدرو اقليمي ـ اكولوژيكي در ايران مركزي، نسبت به كلّ ايران مركزي بيشتر است. نتايج نشان مي‌دهند كه ضرايب رابطه‌هاي اختصاص يافته به ارتباط مخروط‌افكنه ـ حوضه‎ي زهكشي در سراسر قلمرو ايران مركزي ـ كه در طبقه‌بندي‌هاي اقليمي منطقه‎ي خشك و نيمه‎خشك به شمار مي‎روندـ يكسان نبوده و تفاوت‌هاي چشمگيري دارند. اين بررسي همچنين نشان مي‌دهد كه بين برخي از پارامترهاي ژيومورفيك حوضه و مخروط‌افكنه همبستگي معناداري وجود ندارد. لذا پيشنهاد مي‌گردد، در تحليل روابط اختصاصات حوضه- مخروط‌افكنه با روابط ارايه شده در منابع موجود، بهتر است از نتايج حاصل از بررسي‌هاي حوضه‌هاي مجاور و در حدّ امكان، منطقه‌اي استفاده شود.

Introduction Morphometric analysis of relationships between characteristics of basins and alluvial fans is major Hydrogeomorphological issues that this research addressed in the Central Iranian territory. Studies of drainage basin and alluvial fans morphometry have been carried out in many parts of the world. In Iran, such as works include those of Shayan (2003), Mokhtari (2007), Maghsudi (2008), and Goorabi (2009), etc. Morphometric parameters can be used to describe, analyze and compare basins and alluvial fans of different sizes. There is a close correlation between the morphologic features of the basin (e.g., Area, shape, slop, length, aspects, length, width, etc.) And the alluvial fans (e.g., Length, width, area, slope, etc.). In this study, we analyzed 21 morphometric parameters between 30 alluvial fans and basin in central Iran. Methodology This procedure extracted 21 morphometric parameters from 30 drainage basins and alluvial fans in the Central Iran. We used Digital Elevation Model (SRTM90m, ASTER 30m, topographic maps, 1:50000, 1:25000 digital, DEM 10 Mapping Agency) and the software of Arc-Hydro, WMS, and Arc Gis to extracting the characteristics of basins and alluvial fans We scrutinized the borders of basins and alluvial fans with overlapping borders on Land Sat, ASTER, SPOT, and Quick Bird imageries of the study area. Statistical analysis has been carried out in EXCEL, SPSS and Arc Gis softwares. Results and Discussion In this study, we classified the alluvial fans and basins of the study area based on area, location and ecological properties to six groups include; (1) north central Iran, including basins and alluvial fans of Jajrood, Garmsar, Sorkheh, Semnan, and Damghan; (2) West Central Iran, including basins and alluvial fans of Ardestan, Nain, Abarkooh, Marvast, and Bardsir; (3) East of Central Iran includes the basin and alluvial fans of Zahedan region; (4) Middle of central Iranian includes basin and alluvial fans of Tabas, Khoor, and Bajestan; (5) North East, including; basin and alluvial Fan of Torbat and Ferdows; and (6) West of LUT plain. Then, we evaluated the correlation between morphometric parameters of the basin and alluvial fans The Result of this study represents that there is a close correlation between some morphometric parameter of the basins and alluvial fans This study showed that the rate of correlation between morphometric parameters of basins and alluvial fan, largely depend on the scale. Conclusion Based on results of relationships between geomorphic parameters of alluvial fans and basin in central Iran, these parameters are divided into two independent and dependent parameters. The results show that the overall patterns of correlation between the parameters of study area in central Iran are similar to the overall patterns other areas. The correlation between dependent parameters increased with territory decreasing (from central Iran to the smaller area), videlicet it is closely related to the scale. The correlation between morphological parameters of the basins and alluvial fans are increased from large groups into smaller groups in the study area. Among the investigated parameters, correlations between binary parameters of area, slope, and length of drainage basins and alluvial fans are higher than other geomorphic parameters. The correlation between parameters of drainage basins and linked alluvial fans are more in almost homogeneous climatic-ecological regions than the whole of Central Iran. Coefficients assigned to formulas, to express the correlation between alluvial fans and drainage basins in the central Iranian territory- that the classifications are considered arid and semi-arid climatic- are not uniform and there are significant differences. This study shows that the correlation between some parameters of geomorphic basin and alluvial fans are not significant. This study suggests in order analyzing relations between the specificities of the basins and alluvial fans by formulas that are introduced in the available resources, it is better to use from adjacent regions or regional to better results.