تحلیل کیفیت مورفولوژیک کریدور رودخانه ای شهری زاینده رود در اصفهان با استفاده از روش mqi (از پارک ناژوان تا پل اشکاوند)

رودخانه ها در گذر زمان و نیز به طور طبیعی، بستر و کناره های خود را تغییر می دهند اما با دخالت انسان ها فرایند تغییر سریع تر شده است. رودخانه زاینده رود در دهه ها ی اخیر خشک شده و در مسیر حرکت در شهر اصفهان دستخوش تغییرات و   مصنوعی  بسیارزیادی شده  به طوری که کارکرد ژئومورفیک- اکولوژیک خود را از دست داده است. در این پژوهش کیفیت مورفولوژیک رودخانه زاینده رود با مدل mqi (از پارک ناژوان تا پل اشکاوند) بررسی و تحلیل شده است. در این مطالعه، مسیری 16 کیلومتری از رودخانه به 6 بازه تقسیم شد. کیفیت مورفولوژیک بازه های رودخانه ای شامل: پیوستگی فرایندهای رودخانه ای، شرایط مورفولوژیک مجرا و پوشش گیاهی ارزیابی شد. با مطالعات میدانی، استفاده از تصاویر گوگل ارث و پیاده سازی مدل mqi ،نتایج این پژوهش نشان داد که بازه های اول، پنجم و ششم با امتیازهای 0.57،0.66،0.58 در طبقه کیفیت مورفولوژیک متوسط قرار دارند، این بازه ها خارج از محدوه شهری قرار دارند و به لحاظ ژئومورفولوژیک در وضعیت بهتری نسبت به سایر بازه ها هستند. بازه های دوم و سوم و چهارم نیز به ترتیب با امتیازهای 0.38،0.41،0.48، در محدوه شهری قرار گرفته اند و بیشترین تغییرات انسانی را متحمل شده اند و به لحاظ ژئومورفولوژیک در ضعیف ترین حالت قرار دارند . لذا جهت بهبود شرایط مورفولوژیک این رودخانه ، ایجاد جریان پایه حداقلی آب یکی از راهکارهایی جهت احیاء در بازه های رودخانه ارائه شده است. 

morphological quality analysis of urban river corridor of zayandeh rood in isfahan using the mqi method (from najvan park to ashkavand bridge)

1- introductionthe drying of the river in recent years has caused disruption of the river ecosystem and loss of aquatic life and vegetation. among the other main problems of the drying up of the zayandeh rood river, the following can be mentioned: disturbance of the form and process and function of the geomorphology of the river, loss of vegetation, destruction of the aquatic ecosystem and water pollution, reduction of the groundwater level. and finally, the destruction of the environment of the gavkhoni wetland and as a result of it becoming a center of micro-pollution and from the point of view of the city dwellers, tourism has decreased, the view and the beautiful view of the city along the river has also been lost. this issue has also had a negative impact on the microclimate of the city. therefore, it is necessary to carry out deep and comprehensive studies and investigations on the current morphological and hydrological conditions of the river in order to minimize these problems and issues by finding suitable solutions. considering the drying up of zayandeh rood river and severe human changes in this urban river, the purpose of this research is to evaluate the condition and morphological quality of zayandeh rood river in the urban part of isfahan. for this purpose, the mqi morphological quality index method will be used. this method is a new method for classifying the quality and performance of rivers. this method provides an approach to evaluate the morphological quality of rivers and its improvement strategies by considering all river forms and processes, past analysis and adjustment and changes of the river channel.2- methodologyin this research, the morphological quality of the zayandeh rood river has been investigated and analyzed with the mqi model (from najvan park to ashkavand bridge). in this study, a 16 km path of the river was divided into 6 sections. the river morphological quality index (mqi) method consists of two main phases and several sub-phases. the first phase studied the current trends in the assessment of the morphological conditions of the river and includes the investigation of the natural characteristics of the basin, the investigation of the morphology of the river channel and the division of the river. these ranges represent the primary units for evaluating morphological conditionsin the second phase, to evaluate the morphological quality of river basins, the following three aspects are taken into consideration: continuity of river processes, including longitudinal and transverse continuity, the morphological conditions of the conduit including the conduit pattern, cross section shape and bed sediments, vegetation.3-resultto implement the mqi method, the area and route of this 16 km section of the river from najvan park (kalamkar bridge) to ashkavand ring bridge was divided in the inner city and the urban outskirts of isfahan. this division is based on criteria such as changes in the width of the channel, changes in the width of the alluvial plain, the presence of bridges, the presence and changes of marginal vegetation, the presence of artificial structures, the channel planform (straight, winding), the presence or absence of banks it is fixed, the changes in the size of bed sediment, as well as field investigations and visual evaluation of google earth images, and it was divided into 6 intervals. the morphological quality of the river basins including: continuity of river processes, morphological conditions of the channel and vegetation were evaluated. with field studies, the use of google earth images and the implementation of the mqi model, the results of this research showed that the first, fifth, and sixth ranges with scores of 0.57, 0.66, and 0.58 are in the category of medium morphological quality, these ranges are outside the urban area. are located and geomorphologically, they are in a better condition than other ranges. the second, third, and fourth ranges are located in the urban area with scores of 0.38, 0.41, and 0.48, respectively, and have suffered the most human changes and are in the weakest state in terms of geomorphology.4- discussion & conclusionsby classifying the types of river channels and evaluating their morphological and functional quality, it is possible to use many specific management solutions, including various restoration methods and hard to soft engineering to improve their conditions. regarding the revitalization of the zayandeh rood urban river, it is necessary to consider the basic flow of water for the river by respecting the water rights of the river and providing a minimum discharge, reducing the pumping of water from the river upstream for agricultural purposes, especially in the highlands. in the field investigations that were conducted in the study route and six river sections, the complete dryness of the river bed, longitudinal sedimentary barriers were created, some rocky outcrops, islands and sedimentary barriers between channels, mainly artificial sedimentary embankments, destruction of natural vegetation, changes land use and human intervention and stabilization of the banks were clearly observed.