اثرات احداث سد بر ویژگی‌های پیچان رودی قسمت‌های میانی گرگان‌رود

نوع مقاله: مقاله علمی پژوهشی

نویسندگان

1 دانشیار ژئومورفولوژی، گروه جغرافیای دانشگاه مازندران

2 استادیار ژئومورفولوژی، گروه جغرافیای دانشگاه مازندران

3 کارشناس ‏‏ارشد ژئومورفولوژی، گروه جغرافیای دانشگاه مازندران

چکیده

در این تحقیق اثرات احداث سد بر ویژگی‏های پیچان‏رودی قسمت‏های میانی گرگان‏رود در استان گلستان بررسی شده است. محدودة مورد مطالعه بین شهر گنبدکابوس و روستای دیگجه قرار دارد. در قسمت‏های بالادست گرگان‏رود سه سد مخزنی احداث شده است. برای بررسی اثرات احداث این سدها بر ویژگی‏های پیچان‏رودی از عکس‏های هوایی و تصاویر ماهواره‏ای سال‏های 1346، 1380، و 1395 استفاده شد. با رقومی‏کردن مسیر رودخانه در سال‏های یادشده، پارامترهای طول موج، دامنة موج، شعاع قوس، عرض کانال، و میزان مهاجرت کانال رود اندازه‏گیری شد. برای تحلیل تغییرات آب و رسوب داده‏های دو دورة قبل (1346ـ1380) و بعد (1380ـ1395) از احداث بررسی شد. نتایج تحقیق نشان می‏دهد که پس از احداث سد میانگین دبی رودخانه 26 درصد و دبی رسوبات معلق 50 درصد کاهش یافته است. به دنبال کاهش جریان آب، میانگین عرض کانال 50 درصد کاهش یافت. پارامترهای طول موج و دامنة موج تغییرات مشخصی نداشته‏اند. شعاع قوس پس از احداث سد کاهش یافته و با افزایش نسبت شعاع قوس به عرض کانال ظرفیت مهاجرت رود کم شده است. به طور میانگین، میزان فعالیت کانال رود در دورة مورد مطالعه 65/0 متر در سال اندازه‏گیری شد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effects of dam Reservoir on characteristics of meandering river in Gorgan River

نویسندگان [English]

  • Reza Esmaili 1
  • Ghasem Lorestani 2
  • Ghafor Baziar 3
1 Associate Professor of geomorphology, University of Mazandaran, Iran
2 Assistant Professor of geomorphology, University of Mazandaran, Iran
3 MSc in Geomorphology, University of Mazandaran, Iran
چکیده [English]

Introduction
An important characteristic of river is channel form and meandering rivers for active forms. Dams as barriers to water and sediment flow can create discontinuities in fluvial geomorphological conditions. The objectives of this paper are to assess the effects of reservoir on the meandering river morphology. The Gorgan River catchment is located in the southern part of Golestan province with a total area of 11,380 km2. This river is originated from the Alborz Mountains into Caspian Sea. A reach of the river, 44 km long, that is examined in this research is situated in middle Gorgan River, between Gonbad Kaboos city and Digjeh. The construction of reservoir and changes in land use is effective on the main activities that potentially impact water regime, sediment transport and fluvial dynamics in the Gorgan River.  
 
Materials and method   
The data of the flow discharge and suspended sediment load of Gorgan River are available in 1973- 2015 at the Ghazaghli gauge station (73 km downstream from the Golestan reservoir Dam). The hydrological analysis was divided into two periods: before dam construction (1973-2001) and after dam construction (2001-2015). Sediment rating curves were created by daily mean suspended sediment discharge and daily mean water discharges by a power function. The fluvial changes have been measured using aerial photographs of 1967 at a scale of 1:20,000, Landsat satellite images (Landsat TM) 2001 and Google Earth images, 2015. The river was digitized from photographs and satellite images, after they were geographically referenced with the help of ArcGIS 10.2. Meander morphology was described based on some of form parameters such as wavelength, amplitude and radius of curvature, and bank width of the channel. Lateral migration and channel activity was analyzed as geomorphic activity. The normality hypothesis was studied for each parameter and conducted with the Kolmogorov–Smirnov test. If the normality test was not rejected, an ANOVA test was applied. If the normality hypothesis was rejected, the Kruskal–Wallis test was used. In all cases, the significance level assumed was α=0.05, as a threshold for rejecting the null hypothesis. The spatial distribution for these parameters was analyzed in order to change downstream the channel. Thus, the correlation coefficient of Spearman was calculated.
 
Results and discussion  
 
During the pre-dam period (1967–2001), mean discharge below the dam was 14 m3 s-1. These values were 10.5 m3 s-1 after the dam was constructed (2001-2015). Power regression between suspended sediment discharge and water discharge data shows that suspended sediment load is reduced to 50 % after dam construction. The values of wavelength and amplitude show minor differences in the three records and do not show significant differences. The radius of curvature, the length in 1967 (124.7 m) was reduced in 2001 (100.6 m) and 2015 (103 m). The dispersion values show significant differences, with a maximum in 1967 and reductions in 2001 and 2015. Bank width shows significant variations in the three records. In 1967 and 2001, it reached the values of 31 and 33 m, respectively. This is decreased to 15.7 m in 2015(-50% from 1967). Thus, bank width loses half of its value in the pre-dam. In pre-dam period (1977-2001) channel lateral migration was reached 39.3 m and in post-dam (2001-2015) the displacement was recorded to 22.2m. The channel activity during the time period 1967–2015 reached 0.65 m/y. The ratio between radius of curvature and the bank width (Rc/W) is changed from 4.14 in 1967 to 3.04 in 2001 and 7.48 in 2015. These results have indicated that migration capacity is decreased. The stability state shows the spatial distribution of the values. There is no significant relationship between landuse and lateral migration.
 
Conclusion
 
After construction of the three dams, upstream flow discharge is reduced (26%) and mean width of river is reduced (50%) from 2001 to 2015. Suspended sediment discharge has decreased (50%) after the construction of dams. Wavelength and amplitude do not show significant differences throughout the time period. The ratio Rc / Wb doubles from 1967 to 2015. The results show that geomorphological activity is decreased and a static equilibrium was obtained.   

کلیدواژه‌ها [English]

  • meander
  • Golestan province
  • Gorgan River
  • Dam Reservoir
اصغری سراسکانرود، ص. (1395). بررسی پتانسیل تغییرات مورفولوژیک رودخانة شهرچای ارومیه، جغرافیا و برنامه‏ریزی، 57: 49ـ62.

بیاتی خطیبی، م. (1393). بررسی تغییرات پیچان‏رود آجی‏چای در پهنة سیلاب دشت، جغرافیا و برنامه‏ریزی، 49: 55ـ79.

حسین‏زاده، م.م. و اسماعیلی، ر. (1394). ژئومورفولوژی رودخانه‏ای، مفاهیم، اشکال و فرایندها، تهران: انتشارات دانشگاه شهید بهشتی.

عاشوری، م.؛ رضایی مقدم، م. ح. و پیری، ز. (1392). بررسی تغییر مورفولوژی بستر رودخانه پیش و پس از احداث سد با استفاده از HEC RAS و GIS (مطالعة موردی: منطقة پایین‏دست سد ستارخان اهر)، پژوهش‏های جغرافیای طبیعی، 45(1): 87ـ100.

یمانی، م.؛ رحیمی، م. و ویسی، ع. (1394). مورفومتری و مقایسة تغییرات عرضی رودخانة ارس طی سه دهة اخیر (مطالعة موردی: پایین‏دست سد میل مغان)، پژوهش‏هایژئومورفولوژیکمی، 4: 74ـ89.

Adib, A.; Foladfar, H. and Roozy, A. (2016). Role of construction of large dams on river morphology (case study: the Karkheh dam in Iran), Arab J. Geosci, 9: 661, 1-16.

Asghari Saraskanroud, S. (2016). Investigation the Potential of Morphological Change Urmia Shahrchi River, Journal of Geography and planning, 57: 49-62.

Ashouri, M.; Rezaei Moghaddam, M.H. and Piry, Z. (2013). Morphologic Change Assessment of Riverbed Before and after Dam Construction Using HEC RAS Modeland GIS (Case Study: Downstream of SatarkhanDam), Physical Geography research Quarterly, 45(1): 87-100.

Bayati Khatibi, M. (2014). Investigation on Aji-Chay River Meander Changes on Flood Plain, Journal of Geography and planning, 49: 55-79.

Casado, A.; Peiry, J.L. and Campo, A.M. (2016). Geomorphic and vegetation changes in a meandering dryland river regulated by a large dam, Sauce Grande River, Argentina, Geomorphology, 268: 21-34.

Csiki, S.Jc. and Rhoads, B.L. (2014). Influence of four run-of-river dams on channel morphology and sediment characteristics in Illinois, USA, Geomorphology, 206: 215-229.

Lagasse, P.F.; Zevenbergen, L.W.; Spitz, W.J., and Thorne, C.R. (2004). Methodology for Predicting Channel Migration. NCHRP Web-Only Document 67 (Project 24-16), National Cooperative Highway Research Program, Transportation Research Board, Washington, D.C.

Legleiter, C.J. (2015). Downstream effects of recent reservoir development on the morphodynamics of a meandering channel: Savery Creek, Wyoming, USA, River Research & Applications, 31(10): . 1328-1343.

Hosseinzadeh, M.M. and Esmaili, R. (2016). Fluvial geomorphology, concepts, forms and processes, Tehran: Shahid Beheshti University publication.

Hooke, J.M. (1980). Magnitude and distribution of rates of river bank erosion, Earth Surface Processes, 5: 143-157.

Hooke, J.M. (2013). River Meandering, Treatise on Geomorphology, pp. 260-288.

Magdaleno, F. and Fernández-Yuste, J.A. (2011). Meander dynamics in a changing river corridor, Geomorphology, 130: 197-207.

Morais, E.S.; Rocha, P.C. and Hooke, J. (2016). Spatiotemporal variations in channel changes caused by cumulative factors in a meandering river: The lower Peixe River, Brazil, Geomorphology, 273: 348-360.

Ollero, A. (2010). Channel changes and floodplain management in the meandering middle Ebro River, Spain, Geomorphology, 117: 247-260.

Pal, S. (2016). Impact of Massanjore Dam on hydro-geomorphological modification of Mayurakshi River, Eastern India, Environ Dev Sustain, 18: 921-944.

Shields, JR. F.D.; Simon, A. and Steffen, L.G. (2000). Reservoir effects on downstream river channel migration, Environmental Conservation, 27(1): 54-66.

Yamani, M.; Rahimi, M. and Veisi, A. (2015). Morphometry and compare changes across the Aras River during the last three decades (case study: downstream Mil dam of Moghan), Journal of Quantitative Geomorphological researches, 3(4): 74-89.

Yao, Z.; Xiao, J.; Ta, W. and Jia, X. (2013). Planform channel dynamics along the Ningxia–Inner Mongolia reaches of the Yellow River from 1958 to 2008: analysis using Landsat images and topographic maps, Environ Earth Sci, 70: 97-106.

Yousefi, S.; Pourghasemi, H.R.; Hooke, J.; Navartil, O. and Kidov´a, A. (2016). Changes in morphometric meander parameters identified on the Karoon River, Iran, using remote sensing data, Geomorphology, 271: 55-64.