بررسی الگوی پیچان رودی رودخانه ی آجی چای با استفاده از شاخص های زاویه ی مرکزی و ضریب خمیدگی (محدوده ی بین بخشایش تا خواجه)

نوع مقاله : علمی

نویسندگان

1 استاد، ژئومورفولوژی، برنامه ریزی و علوم محیطی، دانشگاه تبریز، تبریز، ایران

2 دانشجوی کارشناسی ارشد، ژئومورفولوژی، برنامه ریزی و علوم محیطی، دانشگاه تبریز، تبریز، ایران

چکیده

رودخانه­ها از سرچشمه تا حوضه­های انتهایی بسترهای متفاوتی را تجربه می­کنند که بالتّبع در هر کدام از این شرایط و مناطق، رفتاری کاملا متفاوت را به نمایش می­گذارند و در نتیجه الگوهای متفاوتی را به خود می­گیرند. محدوده مورد بررسی این پژوهش، بخشی از رودخانه آجی­چای در محدوده­ی بخشایش تا خواجه به طول تقریبی 50 کیلومتر است. در مسیر رودخانه­ی آجی­چای نیز مانند همه رودخانه­ها بدون برنامه­ریزی و در نظر گرفتن پیامدهای ناشی از تغییر مسیر رودخانه در حریم آن کاربری­های زیادی از جمله ساخت ­و سازها، انواع کشت و غیره صورت می­گیرد که در پی تغییر بستر رودخانه تحت تأثیر عوامل مختلف پیامدهای سنگین و زیانباری به بار می­آورد هدف این تحقیق بررسی کمّی خصوصیات و الگوی پیچان­های مسیر مورد مطالعه می­باشد، جهت رسیدن به این هدف و تعیین الگوی رودخانه از شاخص­های مورفومتری ضریب خمیدگی و زاویه مرکزی به عنوان روش مورد بررسی و نقشه­های توپوگرافی با مقیاس 50000/1 خواجه و بخشایش و نقشه­ی زمین­شناسی به مقیاس 100000/1 خواجه و تصاویر ماهواره­ای لندست 8 و نرم­افزار Arc GIS ، به عنوان مواد و ابزار تحقیق استفاده شده است. نتایج به­دست آمده نشان می­دهد که میانگین کل زاویه­ی مرکزی در سه بازه 1/126 درجه می­باشد که طبق نظریه­ی کورنایس در رده 158- 85 قرار می­گیرد که شمای رودخانه در این رده پیچان­رود توسعه­یافته می­باشد. میانگین ضریب خمیدگی در سه بازه­ی مورد بررسی نیز 25/1 می­باشد که بر اساس جدول لئوپولد و ولمن در رده 2- 25/1 قرار می­گیرد که این رده از لحاظ ضریب خمیدگی الگوی پیچان­رودی به­خود می­گیرد، بنابراین با توجه به اینکه رودخانه مورد بررسی در مسیر دارای شیب تقریباً یکنواخت و هموار قرار گرفته­ است عامل توپوگرافی به ویژه شیب، عامل اصلی گسترش الگوی پیچان­رودی می­باشد. 

تازه های تحقیق

-

کلیدواژه‌ها


عنوان مقاله [English]

Investigation of Meandering Pattern of Aji-Chay River Using Central Angle Indices and Curvature coefficient (Area between Bakhshayesh and Khajeh)

نویسندگان [English]

  • Masoumeh Rajabi 1
  • Shahram Roostaei 1
  • Bahareh Akbari 2
1 Professor, Department of Geomorphology, Tabriz University, Tabriz,Iran
2 M.S. Degree in Geomorphology, Tabriz University, Tabriz,Iran
چکیده [English]

1- Introduction
River morphology is the science of knowing the river system regarding general shape and form, dimensions and hydraulic geometry, direction and longitudinal profile of the bed, and the process and quality of its changes. The river plan is divided into three classes of direct, braided (multi-branch) and meandering river in terms of the morphological structure of the river, among which the meandering pattern has attracted the most attention due to its abundance in nature. In order to describe the pattern of the meandering streams, a number of geometric parameters related to the river plan have been defined. By analyzing the frequency and magnitude of these characteristics along the river and at different times, the river changes in the temporal and spatial dimension can be examined. These parameters Such as the length of the pontoon, the width of the pontoon, the width of the river and the length of the river. The purpose of this study is to examine the characteristics and patterns of the Aji Chai River. These parameters are such as the length of meander, the width of meander, river width, and the length of the river. The purpose of this study is to examine the characteristics and pattern of the Aji Chai Rivers’ meanders.

 

2- Methodology
The study area was part of Aji-Chay River (Bakhshayesh​​ to Khajeh) with an approximate length of 50 km, located in the northeast of Tabriz. The following materials are used in this study:1) Topographic map of 1:50000 and 1:250000 scales were used to examine the morphology of the study area,2)Geological maps of 1:250000 and 1:100000 scales for the analysis of geological and tectonic characteristics of the study area and 3)Using Landsat-8 and Google Earth satellite images and the ArcGIS, Excel, Autocad softwares.
The study area was divided into three reaches. Some circles fitted to the meanders in the AutoCAD environment and the geometric characteristics such as wavelength, arc length, and radius of curvature of the circle, which is tangent to the river path, were measured to calculate the curvature coefficient (S = c / v) and the central angle (c/Rπ = ϴ 180). Then specification of each of the circles of the same samples was obtained and then in the EXCEL software, a plot of the samples was drawn.
 
3- Results
Due to the long-range of the study area, the intended path was divided into three reaches. In terms of the central angle index in the first reach, the most frequent central angle was 62.5%, which is related to developed meander pattern. In the second reach, the highest frequency of central angle with 56% was related to the developed meandered pattern. In the third reach also the most frequent central angle was related to the developed meander pattern with a frequency of 57.5%. By comparing the three studied reaches in terms of the central angle index in general, it is concluded that all three reaches have a meandering pattern, in particular, a developed one, so that the average of all three reaches (the first reach 110.2, the second 118.2, and the third 123.1, respectively) are in the developed meandering pattern

 
 category (85-158). In each of three reaches, the most frequent central angle belongs to the developed meandering pattern.
The average curvature coefficient of the reaches, calculated by dividing the sum of frequencies in each reach by the total number of samples of each reach, is as follows: in the first reach, the average curvature coefficient was 1.18 which is in the range of 1-06 – 1.25 showing a sinusoidal pattern. In the second reach, the average curvature coefficient is 1.30, which is in 1.25-2 range, also has a meandering pattern. In the third reach, the average is 1.26, which is the same as the second average in the range 1.25-2 and the pattern is meandering. In general, the pattern of flow in the first reach was sinusoidal and with the increase of arches in the second reach, it changed to the meandering pattern. In the third reach, although, there was a minor reduction trend was, it retained the meandering pattern.
 
4- Discussion and conclusion
Based on the results from the morphometric indices, including the central angle and curvature coefficient in the studied area, the total mean of the central angle in the three reaches is 126.1 degrees, which is in the range of 85-158, showing the developed meandering pattern in the river morphology.
The mean curvature coefficient in the three studied reaches is 1.25, which is in range 1.25-2, takes the meandering pattern in terms of curvature coefficient, so the studied river has a meandering to developed meandering patterns.
The findings of the study indicate that the study area has a nearly uniform and smooth slope, and considering the fact that the existence of a gradient is a significant factor affecting the development of the developed arcs and meander formation, as a result, in determining the river pattern and morphology of the study area, the topography factor had the first priority.
Due to the fact that erodible formations cover most of the area, the factor of lateral erosion in low-slope areas has been effective in the warping of the river path due to the presence of loose and erodible sediments.

کلیدواژه‌ها [English]

  • Meandering
  • Morphometry
  • Central angle index
  • Curvature coefficient index
  • Aji-chay river
Reference
Arshad, S., Morid, S, and Mir Abolghasemi, H. (2008). Assessing the trend of morphologic changes of rivers using remote Sensing: (Case study: Karun river between Gotvand and Farsiat) Journal: Agric. Sci. Natur. Resour, Vol. 14(6), Feb-March, 180-194.
 
Bartholdy, J., and Billi, P, (2002). Morphodynamics of a pseudo meandering gravel bar reach.Geomorphology. 42: 293-310.
 
Biedenharn D.S., Elliot, C.M. and Watson, C.C. (1997). The WES stream investigation and stream bank stabilization.handbook. US. Army Engineering. P 286.
 
Chorley, R., Schumm, S, Sugden, D., (2000).Geomorphology (Domestic Processes Coastal Waterway and Wind), Translation by: Motamed, A, Vol. 4, the Publication of Samt, Tehran.
 
Geographical organization of the Armed Forces, (1996).Topographic map of Bakhshayesh in 1/50000 scale(2).
 
Geographical organization of the Armed Forces (2004).Topographic map of Khajeh in 1/50000 scale(2).
 
Haghi Abi, H., (2004). Theories of the Creation and Evolution of Meanders, Vol. 1, University of Lorestan, 125-137.
Lancaster, S.T., R.L, Bars (2002). A simple model of river meandering andits comparison to natural channels. Hydrol.process No. 16, 1-26.
Leopold, L.B, and Wolman, and J.P, Miller, (1964). Fluvial Processes in Geomorphology, San Farncisco, W.H. Freeman and Co, 21-22.
Leopold, L.B., and Wolman, M.G., (1987). River channel Pattern: Braieded, Meandering and Straight, US. Geo Survey, No. 282.
Mirzavand, M, Ghasemeih, H, Nazari samani, A, Vali, Ai, and Sadatinjad, S.J, (2015). Examining Meandering Pattern of River, Using the Indexes of Curvature Coefficient and Central Angle (Case Study: Babolrud and Sajjadrud Rivers), Journal: Watershed Management Research, Vol. 6, PP.152-161.
 
 
Rezaei Moghaddam, M.H, Sarvati, M.R, and Asghari Saraskanrud, S, (2012). Examining Meandering Pattern of River, Using the Indexes of Curvature Coefficient and Central Angle (Case Study: Ghezel Ozen River: Range between 30km From Mianeh City to Political Border Zanjan), Geography Society of Iran, 10rd Year, vol. 1, 85-102.
 
Sarma, J.N., (2005). Flovial process and morphology of the Brahaputra River in sAssam, Geomorphology, 70 (3-4), 226-26.
Tolouei, S, Hosseinzadeh Dalir, A, Ghorbani, MA, Fakheri Fard, A, and Salmasi, F, (2011). Spatial and Temporal Estimation of Suspended Sediment Load in Aji-chayRiver Using Geostatistics and Artificial Neural Network, Journal of  water and soil Sci, Vol. 21, 93-104.
Xiaolong Song, Guoqiang, Yuchuan, Dong (2016). Experiments on the short-term development of sine-generated meandering rivers, Journal of Hydro-environment Research, 11 (2016) 42–58.
Yamani, M, and Hoseinzadeh, M.M, (2004). Examining Meandering Pattern of River, Using the Indexes of Curvature Coefficient and Central Angle (Case Study: Talar River),Geographical Research, 19rd Year, vol. 2, 144-154.
Yamani, M, Hosseinzadeh, M.M., (2001). The Study About Morphological Changes of Talar River in Mazandaran Coastal Plains, Geographical Research Quarterly, No. 43, 109-122.
 
Yamani, M, Dolati, J, and, Zarei, A, (2010). Influence Hydrogeomorphic Factors on Temporal and Spatial Variations of the Middle Part of the Atrak River,Geographical Research, 25rd Year, vol. 4, 1-24.
Zámolyi A.B.Székely, e. Draganits, G. Timá (2010). Neotectonic control on river sinuosity at the western margin of the Little Hungarian Plain, Geomorphology 122, (3-4) 231-243.