كليدواژه :
منحني ميزان , قزل‌اوزن , سيستم رودخانه‌اي , انحراف رودخانه , اسارت رودخانه
چكيده فارسي :
هدف اين مقاله بررسي شواهد ژئومورفولوژيكي اسارت و انحراف در رودخانه‌هاي حوضه قزل‌اوزن است. براي اين منظور با كمك نقشه هاي توپوگرافي 1:50000 و زمين شناسي 1:100000 منطقه و با توجه به شواهد ژئومورفولوژيكي همچون، انحناي 90 درجهاي و بيشتر در مسير رودخانه، وضعيت تقارن و عدم تقارن توپوگرافي و حوضه ي زهكشي و وجود رسوبات آبرفتي مخروط افكنه اي قديم در سراب رودخانه ها، پنج سرشاخه اي از قزل‌اوزن را كه به‌احتمال‌قوي در طي كواترنري دچار اسارت يا انحراف شده بودند، شناسايي گرديد. با مطالعات ميداني صحت برداشتهاي اوليه از نقشه هاي توپوگرافي، مورد آزمون قرار گرفت. نتايج حاكي از آن است كه وجود شواهد فوق حاكي از تغيير مسير رودخانه‌ها در طي كواترنري است و باعث ايجاد تنگها، پايين افتادن سطح اساس و افزايش رسوب در حوضه شده است. علاوه بر آن تغيير در دبي مقطعي قزل‌اوزن براثر تغيير مسير سرشاخه ها، منجر به افزايش عمل حفر و حمل رسوبات مارني شده كه در اكثر نواحي اين حوضه پراكنده شده‌اند. حفر بيشتر بستر اصلي، فرسايش قهقرايي در سرشاخه ها را افزايش داده و در مجموع بي‌ثباتي را براي كناره‌هاي اين رودخانه به ارمغان آورده است.
چكيده لاتين :
The basis for recognizing the changes in the shape of the earth is the identification and understanding of the amount of displacement of sediments from one region to another, so that this displacement changes the morphology of all those areas. A fluvial system with a certain size, Significant changes in its evolution in the basin area, drainage pattern, Profiles waterways and their geometry was incurred. Having enough information about the changes and the river system evolution is very important to explain the river processes (Vanerberg& Maddy: 2000). In mountainous areas affected by the uplift process, River capture can be organized drainage network (Mather et al: 2000) and affect geomorphological evolution area. Increase the power of river erosion, increasing outflow of the river captor, Increase the Basin area and the knee of captivity among the most obvious of effects are captured by the river (Hamond: 2000). The Ghezel Owzan basin in an area of 50000 KM2 is in the northwest of Iran. Evolution of this system in the recent period of geological had many developments such deviation and capture. In capture, a branch of the drainage network is kidnapped by a branch of the basin area other. usually, regressive erosion occurs by base level changes or the current level and tectonic reasons. The deviation is mainly caused by the erosion of subtracting or side and regressive erosion will disturb the balance. Ghezel Owzan basen is located in the sout east of the Caspian sea. The most hight of the part it is the mountain of Chehel Cheshmeh of Kurdistan and length of the main river is over 550 km. This river passes from the provinces of Zanjan, East Azerbaijan, and Ardabil. Ghezel Ozan received multiple branches along your route in Gilan province, and it was entered into the Sefidrud dem. Basin level is 49400 sq. The basin is located in latitude 34 degrees and 55 minutes to 37 degrees 55 minutes north latitude and 46 degrees 27 minutes east longitude and 49 degrees 20 minutes.
Materials and Methods
In this study, first was identified five basins that may have occurred in them overall change in direction main branches of Ghezel Ozan with the help of topographic maps and the geomorphological evidence. There is some evidence such as curvature 90 degrees and more in the direction of the river, topography asymmetric two sides of the river, drainage basin asymmetric and alluvial deposits of the fans old in the dividing of basins. Then, in field observations, documentary data were reviewed and adapted to environmental conditions. Arc GIS software was extracted from the evidence of captivity or deviation, and was analyzed. The consequences of changes in the river in the fluvial system and changes caused by this phenomenon happens in the location and morphology of rivers has been discussed.
Results and discussion
In examining the phenomenon of deviation and captured in the area of Ghezel Owzan five areas identified and analyzed. These five areas are: 1) Talkhehrood (Mehrabad), 2) Qalehchay, 3) Angoranchay, 4) Yoolkoshty, 5) Goran. In this basin, especially in places that have happened distraction, Significantly landforms is formed. The landforms have been disabled several processes that already changing. With the passage of time, the old form vanished and new forms are formed and are indicated. These changes likely to occur in the future is very high. One of the most important evidence and factors in the erosion bed and Sides of the river and the occurrence of captivity is Specification lithology. Formations located the sides of the river Ghezel Owzan have formed the specific lithology. The lithology of where the two sides the beach have differences together could be considered as evidence for the occurrence of the phenomenon of river captivity.
Conclusion
The effects of geological and geomorphic factors, although considered to be slow, seem to be slow, but they are very important for radical and hydrological changes.The results indicate that there is evidence of change routes above the river that occurred during the Quaternary in Ghezel Owzan and has caused the strait, falling and rising levels of sediment create. In addition, changes in the Dubai sectional Ghezel Owzan redirection of twigs resulted in an increase in drilled practice and transporting marl scattered in most areas of this basin. The drilled more the mainstream, increased erosion regressive in the branches and in total has brought instability to the shores of this river.
