ارزیابی و تحلیل شرایط هیدرومورفولوژیکی رودخانه حاجی‌عرب، شهرستان بوئین‌زهرا

در شرایط محیطی مختلف رودخانه ها پیچیدگی و تنوع زیادی دارند و عوامل مختلف طبیعی و انسانی بر رودخانه ها تاثیرگذار بوده و شرایط هیدرومورفولوژیکی آن ها را تغییر می دهد. در واقع تخریب هیدرومورفولوژیکی به علّت مداخلات انسان و درنتیجه تعدیل کانال رودخانه، یکی از مهم‌ترین انواع و علل تغییرات رودخانه است. روش های متعدّدی برای بررسی هیدروژئومورفولوژی رودخانه ها ابداع شده است. یکی از این روش ها، شاخص کیفیت مورفولوژیکی است که به عنوان پروتکل جدیدی برای ارزیابی کیفیت مورفولوژیکی جریان رودخانه ارائه شده است؛ بنابراین هدف از نوشتار پیش رو طبقه بندی کیفیت مورفولوژیکی رودخانه با استفاده از شاخص کیفیت مورفولوژیکی در رودخانه حاجی عرب واقع در غرب شهرستان بویین زهرا است. این مطالعه شامل دو مرحله اصلی و سه مرحله فرعی است که روی هشت بازه اعمال شده است. در مرحله اوّل موقعیّت عمومی منطقه بررسی شد و در مرحله دوم با استفاده از شاخص های مختلف کیفیت مورفولوژیکی رود ارزیابی شد است. با استفاده از برداشت های میدانی (نقشه برداری و نمونه برداری رسوب) و تصاویر ماهواره ای شاخص های مختلفی ازجمله شاخص عملکردی، شاخص مصنوعی و شاخص تعدیلی بر روی این رودخانه اعمال شده است. نتایج حاصله بیانگر این است که مقدار شاخص کیفیت مورفولوژیکی در بازه های مورد مطالعه بین 82/0% تا 74/0% است که در این میان حداکثر مقدار در بازه های 1، 2، 3، 6 با امتیاز 82/0 و حداقل مقدار در بازه 8 با امتیاز 74/0 است. درمجموع، از نظر کیفیت، رودخانه حاجی عرب در طبقه خوب قرار می گیرد و شرایط مناسبی دارد. شاخص مصنوعی در این رودخانه صفر است که نتیجه عدم دخالت انسان در رودخانه است؛ بنابراین پیشنهاد می شود که از این رودخانه با کیفیت مورفولوژیکی خوب با مدیریت درست و به جا حفاظت شود.

The Assessment and Analysis of the Hydromorphological Condition of Haji- Arab River, Bouein Zahra County

Rivers have a lot of complexity and diversity in different environmental conditions, and various natural and human factors affect rivers and change their hydromorphological conditions. In fact, hydromorphological degradation is one of the most important types and causes of river changes which happens due to human interventions and consequently the adjustment of the river channel. Several methods have been developed to study the hydrogeomorphology of rivers. One of these methods is the morphological quality index, which has been proposed as a new protocol to assess the morphological quality of river flow. The present study aims to classify hydromorphological quality of the HajiArab River (which is located in the west of BouinZahra city) by Morphological Quality Index (MQI). In this study, two main phases and three subphases are used for each phase and applied to eight spans. Various indicators such as: functionality index, artificiality index and adjustment index have been applied on this river. The results show that the amount of MQI in the studied intervals was between 0.82 to 0.74%. Among these, the maximum value was in the spans of 1,2,3,6 with a score of 0.82, while the minimum value was in the span of 8 with a score of 0.74.  In terms of quality, HajiArab River is on a good class and has good conditions. The functionality index in this river was zero, which was the result of nonintervention of human in the river. Therefore, it is suggested to protect HajiArab River appropriately by proper management.Extended Abstract1IntroductionSeveral tools have been developed in Europe and worldwide to assess hydromorphology and the methods for physical habitat assessment are the most common approach. These methods generally consist of surveying, characterisation and classification of physical habitat elements, mainly focusing on instream features. River management often focuses on individual span of river networks. However, the character and dynamism of river spans depends not only upon natural processes and human interventions within the span, but also within the catchment, particularly upstream of the span.The Italian Environment Minister has recently issued the WFD monitoring and classification standards, introducing the Morphological Quality Index (MQI), which is part of IDRAIM, as a new and innovative protocol for stream morphological quality assessment. This study aims to apply Morphological Quality Index (MQI) for the hydromorphological analysis of HajiArab River.2Materials and MethodsHajiArab River is one of the southern rivers of Qazvin plain. The river flows generally from south to north. The total area of HajiArab Catchment is 130,657 square kilometers and the length of the study span is 7.45 kilometers. Regarding geological divisions of Iran, this region is part of the UrmiaBazman magmatic belt of Central Iran. The climate of this area is temperate to warm and dry. The average annual flow rate was 0.62 m3/s and the maximum flow was 152 m3/s.MQI has two phases and the components of the evaluation method. The first phase of the method is dividing the four steps. In step 1, a basic investigation of geology, geomorphology, climate, and the land use of the whole catchment is carried out. In step 2, lateral confinement is analyzed in more details, and three valley settings are differentiated: confined, partly confined, and laterally unconfined channels. In step 3, stream channels are classified into seven river morphologies (straight, sinuous, meandering, sinuous with alternate bars, wandering, braided, anastomosed). Step 4 considers additional discontinuities to further subdivide the stream spans, including hydrological discontinuities, bed slope, or relevant changes in channel width, alluvial plain width, or bed sediment. The second phase of the method is structure and key components of the evaluation procedure. The three aspects are considered for the assessment of the morphological quality of river spans. These aspects are analyzed in terms of three components: (i) the geomorphological functionality of river processes and forms; (ii) artificiality; and (iii) channel adjustments.A total score was computed as the sum of scores across all components and aspects. The Morphological Alteration Index (MAI) is first defined as follows: MAI = Stot/SmaxIn which Stot is the sum of the scores, and Smax is the maximum score that could be spaned when all appropriate indicators are in class C. The Morphological Quality Index is then defined asMQI = 1−MAIThe following classes of morphological quality were defined: (i) high, 0.85≤MQI≤1; (ii) good, 0.7≤MQIb0.85; (iii) moderate, 0.5≤MQIb0.7; (iv) poor, 0.3≤MQIb0.5; (v) bad, 0≤MQIb0.3.3Results and DiscussionThe HajiArab River was divided to eight spans based on investigating morphological quality. Regarding to physiographic units, spans 1, 2 and 3 are located in the low plain unit, and spans 4 to 8 are located in the intermontane plain unit. All spans are partly confined with hillslopes or ancient terraces and confinement degree is between 10 and 90 percentages. All of these spans as partly confined channels were classified based on their planimetric characteristics using sinuosity index and braiding index. Except for span 3 (multithread), other spans are singlethread channel.There are no changes in the continuity of sediment and wood flux in all spans. There is no floodplain or negligible in the spans 1, 2, 4 and 5 but discontinued floodplain in the spans 3, 6, 7 and 8. The valley slope is connected to a considerable part of the river in the spans 1, 2, 4, 5 and 8, but connected to a small part of the river in the span 3 and connected to full part of the river in the spans 6 and 7. Except for span 7, all spans have no bank reiteration. All spans have potentially erodible corridors. Moreover, bed forms are compatible with the slope of the valley in the spans 3, 4, 5 and 8, while they are not compatible with the slope of the valley in the spans 1, 2, 6 and 7.  There are no heterogeneous changes of forms in all spans except for the span 3. There are no active flood plain forms in the all spans except for spans 3 and 5 with secondary channels. In all spans, there is no change of cross sections, no natural bed heterogeneity, and no large woods. Linear expansion of vegetation is less than 33%  in the all spans. They showed low width channelrelated vegetation except for spans 6 and 7 with medium width channelrelated vegetation.There is no specific changes  channelforming discharge and discharge, no structure, no changes in sediment discharge due to human interventions, no crossing structures, no protected banks along the river, no embankment,  no structures along the river, no sediment movement, no wood movement, no vegetation cut by humans in all of spans.There is a change of channel pattern in the spans of 4, 5, 7 and 8 from braided to meandering pattern, drastic changes in channel width in the spans of 4, 5, 6, 7 and 8, low changes of the base level in the spans of 1, 2, 3, 4 and 6, medium changes of the base level in the spans of 5, 7 and 8.4ConclusionThe results show that the amount of MQI in Haji Arab River is between 0.82 to 0.74% and in terms of quality HajiArab river is in a good category and has good conditions. The artificiality indicators in this river are zero, which is the result of nonintervention of human in the River. Finally, it is recommended that protection of the HajiArab River and its corridors is essential. Other aspects of the hydromorphological conditions of the River, including physical habitat assessment, hydrological regime assessment, and the habitat of the river corridor should be considered in the future studies. It is better to study the impact of the dam under construction upstream on the hydromorphological conditions of the HajiArab River in the future.