Environmental Erosion Research

fa تبیین ارتباط پراکندگی فرونشست و تغییرات لندفرم‌های کواترنری در دشت تهران Explaining the relationship between subsidence distribution and Quaternary landform changes in the Tehran Plain تحلیل فضایی عوامل فرساینده، و استخراج الگوهای پراکندگی و انتشار فرسایش مستخرج از پایان‌نامه / رساله / طرح پژوهشی <div style="text-align: justify;">فرونشست زمین به عنوان حرکت رو به پایین سطح زمین، نقش مهمی در شکل‌دهی ویژگی‌های ژئومورفولوژیکی در مناظر مختلف دارد. در این پژوهش برای بررسی فرونشست دشت تهران از تصاویر راداری ماهواره سنتینل1 سال 2022 و تکنیک تداخلسنجی راداری خط پایه کوچک (<a name="_Hlk188285659">SBAS</a>) استفاده شده است. همچنین با استفاده از داده‌های چاه‌های پیزومتری، منحنی تغییرات تراز آب زیرزمینی آبخانه دشت تهران برای سال های 1381 تا 1401 به دست آمد. به منظور مشاهده مستقیم اثرات ژئومورفولوژیک فرونشست در دشت تهران اقدام به انجام بازدید میدانی برای 20 نقطه از مناطق متاثر از فرونشست زیاد شد. نتایج نهایی، نشان‌دهنده نرخ جابه جایی بین 163.3- میلیمتر تا 3+ میلیمتر در سال در راستای خط دید ماهواره است که عمده فرونشست‌های دشت تهران در بخش‌های مرکزی و غربی دشت دیده می‌شوند که بیشینه آن در مرکز و شرق شهرستان شهریار و شمال&lrm;غربی شهرستان اسلام‌شهر قرار دارد. حاشیه پهنه فرونشست به بخش جنوب‌غربی شهر تهران نیز کشیده شده است و نرخ تا حدود 25 میلیمتر در سال را نشان می‌دهد. نمودار مقدار تجمعی استاندارد شده سطح آب زیرزمینی موید دوره‌های افت شدید آب زیرزمینی برای همه چاه‌ها است. ایجاد و گسترش گالی‌های دیواره پادگانه‌های قدیمی، جدا شدن دیواره بستر رودخانه به شکل ترک‌های جداره و در سطح آن از تغییرات رایج ژئومورفولوژیک در دشت تهران است.</div>   <a name="_Hlk188286383">1- Introduction</a> Land Subsidence, as the downward movement of the land surface, plays an important role in shaping geomorphological features in different landscapes. Subsidence significantly affects the formation of river geomorphology by changing sediment distribution patterns, channel morphology, and basin evolution. Studies have shown that subsidence can lead to channel deviation, creating head-changing deviations, and increasing river gradients. In addition, subsidence affects sediment distribution, shoreline patterns, and channel mobility. The Tehran Plain aquifer has been subsiding over the past three decades, and the magnitude of this subsidence does not show a uniform distribution. Previous studies have attributed excessive groundwater extraction to the subsidence phenomenon in recent years. It seems that geomorphological diversity with different sedimentary characteristics can play a different role in the speed of expansion and secondary consequences of subsidence in this area. In order to directly observe the geomorphological effects of subsidence in the Tehran Plain, a field visit was conducted to about 20 points in areas affected by significant subsidence. 2- Methodology This area is part of the Tehran-Karaj aquifer and includes the cities of Islam Shahr, Shahriar, Qods and Baharestan, Tehran city and parts of the cities of Malard, Fardis, Robat Karim and Rey. The northern border of this area is limited to the slopes of the Alborz mountain range and includes the Tehran and Karaj alluvial fans and alluvial plain. In this study, Sentinel 1 satellite radar images in VV polarization were used in the period of 2022 with a time interval of 12 days. The number of selected images is 27 pieces. The small baseline radar interferometry technique (SBAS) and GMTSAR software were used to study Land subsidence. In order to directly observe the geomorphological effects of subsidence in the plain of Tehran, a field visit was conducted for about 20 points of areas affected by high subsidence. 3- Results The final results show a displacement rate of -163.338 mm to +38.3 mm per year along the satellite line of sight. According to the obtained displacement map, most of the subsidence of the Tehran Plain is seen in the central and western parts of the plain, with its maximum in the center and east of Shahriar County and northwest of Eslam Shahr County. The margin of the subsidence zone also extends to the southwestern part of Tehran City, showing a rate of up to 25 mm per year. The graph of the standardized cumulative groundwater level confirms periods of severe groundwater decline for all wells, although in some wells the water level continues to decline, while in others it has increased after a while, which may be due to groundwater consumption management or other possible changes such as sewage leakage into the aquifer. Photographs taken from the Karaj Riverside areas between the cities of Shahriar and Islamshahr, which are located in an area with high subsidence (between 80 and 150 mm per year), show the creation and expansion of gullies and the separation of the riverbed wall in the form of cracks in the wall and on its surface due to subsidence. 4- Discussion & Conclusions A large part of the area affected by subsidence is located in Shahriar County, but due to the expansion of construction and agricultural lands, it is not possible to study its geomorphological changes in this area, and we can only focus on the effects of subsidence on human structures and ground cracks. The graph of the standardized cumulative value of the groundwater level confirms the periods of severe groundwater decline for all wells. Considering the dispersion of the selected well locations and the spatial and sedimentary differences, a different behavior of groundwater level changes compared to subsidence is evident and it can be concluded that the decrease in groundwater level is not the only reason for the dispersion of subsidence in the Tehran plain aquifer and that other different contributing factors such as sedimentary structure and soil type and human impacts such as possible sewage leakage are involved. Field visits to the maximum subsidence areas show geomorphological changes caused by subsidence in the form of cracks in the ground and river walls, as well as the creation of gullies in the walls of old river embankments. فرونشست زمین, دشت تهران, لندفرم‌های کواترنری, تکنیک تداخل سنجی راداری,SBAS Land subsidence, Tehran Plain, Geomorphological effects, Radar interferometry technique, SBAS. 24 41 http://magazine.hormozgan.ac.ir/browse.php?a_code=A-10-735-2&slc_lang=fa&sid=1 sasan zangenehtabar ساسان زنگنه‌تبار zangenegeo154@gmail.com 10031947532846009740 10031947532846009740 No Faculty of Geography, University of Tehran, Tehran, Iran دانشکده جغرافیا، دانشگاه تهران، تهران Mojtaba Yamani مجتبی یمانی myamani@ut.ac.ir 10031947532846009741 10031947532846009741 Yes Faculty of Geography, University of Tehran, Tehran, Iran دانشکده جغرافیا، دانشگاه تهران، تهران Mohammad Sharifikia محمد شریفی کیا sharifikia@modares.ac.ir 10031947532846009742 10031947532846009742 No Faculty of Geography, University of Tarbiat Modarres, Tehran, Iran گروه سنجش از دور، دانشکده علوم انسانی، دانشگاه تربیت مدرس، تهران Seyed Mosa Hossieni سید موسی حسینی smhosseini@ut.ac.ir 10031947532846009743 10031947532846009743 No Faculty of Geography, University of Tehran, Tehran, Iran دانشکده جغرافیا، دانشگاه تهران، تهران masoomeh amighpey معصومه آمیغ پی amighpey@yahoo.com 10031947532846009744 10031947532846009744 No Land Surveying Department, National Cartographic Center, Tehran, Iran اداره ترازیابی دقیق و تداخل‌سنجی راداری، اداره کل نقشه‌برداری زمینی و بنیادی، سازمان نقشه‌برداری کشور، تهران