تحلیل هیدرومورفولوژیک رودخانه کرج در بازه شهری از بیلقان تا پل راه‌آهن

توسعه شهری و تغییر کاربری اراضی، آسیب‌های جدی بر کیفیت و شرایط تعادل ژئومورفولوژیک، ظرفیت آبگذری و خدمات زیست‌بوم رودخانه وارد کرده است. از طرفی این تغییرات و دخالت‌های انسانی، پایداری محیطی محدوده را تحت‌تاثیر قرار داده است. برای مدیریت و جلوگیری ازدست‌رفتن عملکردهای طبیعی و ژئومورفولوژیک رودخانه‌ها ضرورت ارزیابی کیفیت مورفولوژیک رودخانه وجود دارد. در رودخانه کرج به دلیل گسترش شهرنشینی، تجاوز به بستر و حریم رودخانه، آبراهه‌سازی، برداشت شن و ماسه و غیره، آسیب های جدی بر اکوسیستم رودخانه تحمیل شده است. در پژوهش حاضر، کیفیت هیدروژئومورفولوژی رودخانه کرج در بازه شهری کرج (از پل بیلقان تا پل راه‌آهن) مورد ارزیابی قرار گرفت. با استفاده از شاخص هیدروژئومورفولوژیکی ihg در طول مسیر اصلی رودخانه، حوضه به هفت بخش (بازه) تقسیم شد و مقدار این شاخص برای هر بازه تعیین گردید. شاخص ihg تعداد 9 پارامتر را در سه گروه (کیفیت عملکرد رودخانه‌، مورفولوژی آبراهه، پوشش گیاهی کنار رود) ارزیابی می‌کند. مقدار هر پارامتر بین 1 تا 10، متناسب با وضعیت طبیعی و عملکرد حوضه رودخانه قرار دارد. بر اساس نتایج این تحقیق، بازه‌های 1، 2، 3، 4، 6 و 7 از کیفیت هیدرومورفولوژی ضعیف؛ و بازه 5 به دلیل دخالت‌های انسانی (از جمله تغییر در الگوی مورفولوژی، ایجاد سازه‌های مهندسی، قطع پیوستگی آبراهه اصلی و سیلاب‌دشت)، از کیفیت خیلی ضعیف برخوردار هستند. همچنین، کیفیت هیدروژئومورفولوژی بازه شهری رودخانه کرج به دلیل گسترش فضای شهری و سکونتگاهی، تاسیسات شهری و استخراج بی‌رویه شن و ماسه، بیشترین اثرات منفی را دارد. نتایج نشان می‌دهد که شاخص ihg نشانگر و حسگر مناسبی برای ارزیابی کیفیت هیدروژئومورفولوژیکی رودخانه ها است.

hydro-morphological analysis of karaj river in the urban area from beylqan to the railway bridge

urban development and land use change have seriously damaged the quality and conditions of geomorphological equilibrium, drainage capacity and river ecosystem services. on the other hand, these changes and human interventions have affected the environmental sustainability of the area. to manage and prevent the loss of natural and geomorphological functions of rivers, it is necessary to assess the morphological quality of the river. in the karaj river, due to the expansion of urbanization, encroachment on the riverbed, channeling, sand extraction, etc., serious damage has been inflicted on the river ecosystem. in the present study, the hydro-geomorphological quality of the karaj river in the urban area of karaj of iran (from beylqan bridge to the railway bridge) was evaluated. using ihg hydro-geomorphological index along the main river, the basin was divided into seven sections and the value of this index was determined for each section. the ihg index evaluates 9 parameters in three groups (functional quality, channel quality, riparian quality). the value of each parameter calculated between 1 and 10 depending on the physical state and performance of the river basin. based on the results of this study, sections of 1, 2, 3, 4, 6 and 7 have poor hydro-morphological quality; and section 5 due to human activity (including changes in morphological pattern, construction of engineering structures, disconnection of the main waterway and floodplain) have very poor quality. also, the hydro-geomorphological quality of the urban area of karaj river has the most negative effects due to the expansion of city and residential space, urban facilities and uncontrolled extraction of sand. the results show that the ihg index is a good indicator and sensor for assessing the hydro-geomorphological quality of rivers. extended abstract1-introductionthe development of residential areas around river systems played a major role in controlling the geomorphological features of rivers, especially the narrowing of rivers. the direct consequences of the human role in which human activity affects through engineering operations such as channeling, dam construction, diversion and culverting, have long been known. to prevent the destruction of rivers and aquatic ecosystems, it is necessary to think of a solution and adopt an approach to protect the environment and the physical functioning of rivers. this approach was considered in leading countries in the field of river rehabilitation, all on the maximum effort is to return to the state before manipulating the river. concepts of hydrology and geomorphology for river rehabilitation projects include variability in time and space, the impact of local and downstream parts effects on waterway processes. understanding hydro-geomorphic variability in river ecosystems is important and necessary to devise and provide effective solutions for the protection and recovery of river systems. hydro-geomorphological index (ihg) to implement 2000/60/ eu protocol to reduce the destruction of river systems, identify, understand, solve or reduce environmental problems of these systems, improve and maintain their performance and normality, certificate and diagnose their hydro-geomorphological value is used to educate administrators and students and raise awareness in the community due to the expansion of urbanization, encroachment on the river, and organizing the river with traditional engineering methods in the karaj river. the purpose of this study was to evaluate and analyze the impact of human interventions on the hydro-geomorphological conditions of the river, including morphological, hydrological, ecological, and vegetation conditions, and identify vulnerable sections and provide solutions to organize and restoration the river. therefore, in this study, the evaluation of hydro-geomorphological conditions of karaj river in urban areas from beylqan bridge to railway bridge is investigated using hydro-geomorphological index (ihg). 2-materials and methodsthe karaj drainage basin is located on the southern hillsides of the central alborz mountain. the study area includes the karaj river urban area and beylaqan bridge to rrailway parts of the river, a length of approximately 9 km. data used in this study include topographic maps 1: 25000 and 1: 50000 scales, geological maps 1: 100000 scale, digital elevation model (dem) 12.5 m radar palsar sensor, landsat tm, oli satellite images and google earth images and data in the hydrometric station includes the discharge and sediment of beylqan and sierra stations. in order to achieve the objectives of the research, evaluation and hydro-morphological analysis of the karaj river has been performed using the hydro-geomorphological index (ihg). in river research, the ihg index includes nine parameters divided into three categories: 1-functional quality, 2- channel quality and 3- riparian quality. each parameter is scored on a scale of 1 to 10 based on its physical state and performance in relation to the river system, a maximum rating of 10 implies excellent performance or the presence of minimal influences that do not detract from the river system’s naturalness. 3- results and discussionbased on three quality parameters of hydro-geomorphology (ihg) including functional quality, channel quality and riparian quality, sections no. 1, 2, 3, 4, 6 and 7 with poor status and section no. 5, which includes the project area of alborz lake has of very poor quality. from this point of view, anthropogenic interventions in the main channel and the river bank have the greatest impact on the physical performance of the system. this factor reducing the functional quality both in terms of reducing river water flow and in terms of sediment supply and movement, morphology and vegetation of the river. so that the development of urban space as a change imposed on the river has caused a different response of the river, disturbing the balance of the river and its natural function. finally, the nature of the hydrogeomorphic system of the river has changed. 4- conclusionthe results of a hydro-geomorphological assessment of three parameters in the river system: (1) functional quality, (2) channel quality, and (3) riparian quality, different behavior is expressed in response to various human actions and forces induced in the channel and flood plain of each functional component. the results of functional quality demonstrate that changes in the riverbed caused by human activity (recreational use, urbanization and specific projects on riverbanks and riverbeds, sand extraction) have had a direct impact on its quality. inadequate morphological quality can be caused by human intervention through the construction of transverse infrastructure such as bridges, mining, diversions and canals, which destroys the nature and diversity of vegetation and endangers the dynamics of rivers and the ecological status of the channel. the quality of riparian due to channeling and expansion of urban physical space causes the destruction of vegetation and biodiversity living in them, where the naturalness of coastal vegetation has changed as a result of these human actions and there is no connection between riparian area and bed vegetation.