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پژوهش های جغرافیای طبیعی، جلد ۴۹، شماره ۴، صفحات ۶۵۷-۶۶۶
عنوان فارسی اثرات احداث سد بر ویژگی‌های پیچان رودی قسمت‌های میانی گرگان‌رود
چکیده فارسی مقاله در این تحقیق اثرات احداث سد بر ویژگی‏های پیچان‏رودی قسمت‏های میانی گرگان‏رود در استان گلستان بررسی شده است. محدوده 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، دامنه موج، شعاع قوس، عرض کانال، و میزان مهاجرت کانال رود اندازه‏گیری شد. برای تحلیل تغییرات آب و رسوب داده‏های دو دوره 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 دامنه 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 دوره مورد مطالعه 65/0 متر در سال اندازه‏گیری شد.
کلیدواژه‌های فارسی مقاله استان گلستان، پیچان‌رود، سد مخزنی، گرگان‌رود،
عنوان انگلیسی Effects of dam Reservoir on characteristics of meandering river in Gorgan River
چکیده انگلیسی مقاله 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.   
کلیدواژه‌های انگلیسی مقاله meander, Golestan province, Gorgan River, dam reservoir
نویسندگان مقاله رضا اسماعیلی |
دانشیار ژئومورفولوژی، گروه جغرافیای دانشگاه مازندران

قاسم لرستانی |
استادیار ژئومورفولوژی، گروه جغرافیای دانشگاه مازندران

غفور بازیار |
کارشناس ‏‏ارشد ژئومورفولوژی، گروه جغرافیای دانشگاه مازندران

نشانی اینترنتی https://jphgr.ut.ac.ir/article_67215_b1629acf893ea6efd01ff9f5bcf0ef94.pdf
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