فهرست مطالب

پژوهش های فرسایش محیطی - سال نهم شماره 1 (پیاپی 33، بهار 1398)
  • سال نهم شماره 1 (پیاپی 33، بهار 1398)
  • تاریخ انتشار: 1398/02/11
  • تعداد عناوین: 5
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  • ایرج رحیمی، مرتضی سیدیان*، حامد روحانی، رضا احمدی صفحات 1-26

    خاک یکی از مهم ترین عناصر منابع طبیعی در هر کشور است. در مناطقی که فرسایش کنترل نمی شود، خاک ها به تدریج فرسایش می یابد و حاصلخیزی خود را از دست می دهد. یکی از پیامدهای کاهش حاصلخیزی خاک، عدم امکان تامین غذای کافی است. معمولا برای حفاظت خاک و جلوگیری از فرسایش، دو روش مستقیم و غیرمستقیم وجود دارد. یکی از روش های مستقیم جلوگیری از فرسایش، احداث بندهای اصلاحی است. این سازه ها در بستر آبراهه ها و عمود بر جریان ساخته می شود تا سرعت آب و قدرت فرسایش رواناب در اثر کاهش شیب بستر را کاهش دهد. هدف پژوهش حاضر، اولویت بندی مکانی محل احداث بندهای سنگی ملاتی و گابیونی در حوزه ی آبخیز قورچای رامیان براساس روش های تصمیم گیری چند معیاره است. اولویت بندی بر اساس معیارهای تاثیرگذار مانند فیزیوگرافی، هیدرواقلیم، زمین شناسی و خاک شناسی و عوامل اقتصادی اجتماعی با استفاده از مدل AHP و سیستم اطلاعات جغرافیایی (GIS) انجام شد. وزن معیارهای اقتصادی اجتماعی، هیدرواقلیم، فیزیوگرافی، خاک و زمین شناسی به ترتیب برابر با 0/409، 0/124، 0/058 و 0/409 است که  میزان تاثیر معیارها را بر مکان یابی محل احداث بند گابیونی و سنگی ملاتی نشان می دهد. بر اساس اولویت بندی که در بین وزن ها صورت گرفته ، اولویت های 1 تا 5 برای احداث بندهای سنگی ملاتی به ترتیب متعلق به زیرحوزه های 14، 10، 13، 6 و 9 است. زیرحوزه ی 14 با وزن 0/304 به عنوان اولویت اول و زیرحوزه ی شماره 1 با وزن 0/129 در اولویت آخر است. از بین زیرمعیارها، زیرمعیار حساسیت به فرسایش سازند با وزن 0/36 دارای بیشترین تاثیر و زیرمعیار ضریب سیل خیزی و درصد شیب با وزن 0/05 دارای کمترین تاثیر در انتخاب اولویت اول یعنی زیر حوزه ی 14 است. براساس اولویت بندی که در بین وزن های نهایی 62 زیرحوزه با آبراهه درجه 2 برای احداث بندهای گابیونی صورت گرفت، اولویت های 1 تا 5 به ترتیب به زیرحوزه های 36، 35، 34، 32 و 57 تعلق دارد. زیر حوزه ی شماره ی 36 با وزن 0/453 به عنوان اولویت اول و زیر حوزه ی شماره ی 1 با وزن 0/113 به عنوان اولویت آخر برای احداث بند گابیونی پیشنهاد شد.

    کلیدواژگان: اولویت بندی مکانی، سیستم اطلاعات جغرافیایی، فرایند تحلیل سلسله مراتبی، قورچای
  • زهرا یارمرادی، بهروز نصیری*، غلام حسن محمدی، مصطفی کرم پور صفحات 27-44

    امروزه معضل توفان های گرد و خاک به بحرانی منطقه ای و جهانی تبدیل شده است. پژوهش حاضر بر آن است که با استفاده از مدل عددی، تصاویر ماهواره ی MODIS و شاخص AOD و نقشه های همدیدی، به تعیین منابع گرد و غبار و چگونگی حرکت آنها بر فراز نیمه ی شرقی ایران طی فصل گرم سال بپردازد. در مرحله ی اول با استفاده از داده های مشاهداتی، تصاویر ماهواره و شاخص عمق اپتیکی گرد و غبار، توفان های گرد و غبار فصل گرم طی دوره ی آماری 2010 تا 2018 مشخص شد. سپس به بررسی عوامل همدیدی موثر بر رخداد این پدیده پرداخته شد؛ برای این امر با مراجعه به تارنمای مرکز اروپایی، پیش بینی میان مقیاس جوی (ECMWF) داده های دما، فشار تراز دریا (SLP)، مولفه های مداری و نصف النهاری باد، ارتفاع ژئوپتانسیل در ترازهای 850، 500 و250 هکتوپاسکال با دقت فضایی 0/25 * 0/25 درجه دریافت شد. در مرحله ی بعد برای منشایابی این توفان ها، از مدل پخش لاگرانژیHYSPLIT  به روش پسگرد استفاده شد. نتایج حاصل از مطالعات همدید نشان داد زمانی که یک سلول مستقل پرفشار بر شمال شرق افغانستان و شمال شرق ایران، همچنین سلول کم فشار بسته ای بر جنوب غرب افغانستان وجود دارد، گرادیان شدیدی بین این مناطق ایجاد و باعث می شود سرعت باد در سطح زمین به بیش از 14 متر بر ثانیه برسد. اختلاف شدید فشاری و دمایی در منطقه، نبود رطوبت و زاویه ی تابش بالا سبب می شود گرد و غبار بیابان های خارج از مرزهای شمالی و شرقی به منطقه هدایت شود. همچنین در این فصل، منطقه تحت تسلط پر فشار جنب حاره آزور قرار دارد که بلوکه شدن آن در سطوح بالا به تداوم گرد و غبار در شرق ایران به مدت سه روز منجر شده است. خروجی های مدل و تصاویر ماهواره نشان داد که به طور کلی بیش از 90 درصد منابع اصلی غبار برای توفان های گرد و غباری شرق ایران، محدوده ای در حد فاصل بیابان های مرکزی ترکمنستان، قزاقستان، افغانستان و دشت سیستان است.

    کلیدواژگان: ردیابی، گردوغبار، HYSPLI، MODIS
  • محمد پوستی*، حسین غلام علیان صفحات 45-61

    سازند آغاجاری با سن میوسن میانی تا پلیوسن، آخرین واحد گروه فارس است. سنگ رخساره های شناخته شده در نهشته های این سازند شامل ماسه سنگ آهکی، مارن، آهک و سیلتستون آهکی است. ستبرای این سازند در برخی از مناطق پس خشکی بندرعباس به بیش از 3000 متر هم می رسد. مطالعات صحرایی و میکروسکوپی روی 50 نمونه ی برداشت شده از این سازند در محدوده ی مورد پژوهش و نمونه های گرفته شده از سری هرمز (مربوط به چند گنبد) نشان می دهد که این سازند دارای دانه های آواری (عمدتا کوارتز پلی کریستالین و کوارتزهای با خاموشی موجی)، خرده های سنگواره ها ، کانی های تیره (اکسید و هیدروکسیدهای آهن)، آلبیت، ارتوکلاز و کانی های فرعی مسکویت و کلریت است که همگی در یک زمینه ی آهکی قرار دارد. آزمایش هایXRF  و میکروپروب سه نمونه از اولیژیست های موجود در سازند آغاجاری و سری هرمز، بیانگر این است که منشا اولیژیست ها احتمالا به فرسایش سری هرمز بازمی گردد. فراوانی کوارتزهای دارای خاموشی موجی در سازند آغاجاری نیز منشا دگرگونی را برای آنها نشان می دهد و احتمالا توسط عوامل حمل و نقل از پهنه ی ساختاری سنندج سیرجان به این حوضه ی رسوبی منتقل شده است.

    کلیدواژگان: اولیژیست، کوارتز، سازند آغاجاری، سری هرمز، سنندج سیرجان، منشایابی
  • مژده محمدی *، محمدرضا اختصاصی صفحات 62-84

    هندسه فراکتال، زبان ریاضی است که می تواند به صورت ابزاری کمی برای بررسی ژئومورفولوژی حوضه ی آبخیز و مدل سازی بسیاری از پدیده های پیچیده ی طبیعی استفاده شود. در حقیقت پدیده های ژئوفیزیکی مانند حوضه های آبخیز، پدیده هایی فراکتالی هستند که الگوی فراکتالی در رفتارهای آنها قابل بررسی است. شناخت عوامل ژئومورفومولوژیکی و عملکرد آنها، اهمیت بالایی در مدیریت حوضه دارد. پژوهش حاضر با هدف تحلیل رفتار فراکتالی حوضه آبخیز عقدا، از طریق محاسبه ی ابعاد فراکتال شکل حوضه و شبکه زهکشی و مقایسه ی نتایج به دست آمده با 18 ویژگی ژئومورفولوژیک حوضه ی مورد مطالعه انجام شده است. نتایج نشان داد که در بین زیرحوضه های مستقل، زیرحوضه ی T8 با بعد فراکتال 1/47 و در میان زیرحوضه های تجمعی، زیرحوضه ی To3 با بعد فراکتال 1/6 دارای بیشترین بعد فراکتال شبکه زهکشی هستند و بیشترین بعد فراکتال شکل حوضه را نیز به ترتیب با مقادیر 1/05 و 1/08 به خود اختصاص می دهند. نتایج حاصل از این بررسی، روابط معنی داری بین ابعاد فراکتال شکل حوضه و شبکه زهکشی با ویژگی های ژئومورفولوژیک نشان می دهد. بالاترین ضریب همبستگی متعلق به روابط رگرسیونی بین مجموع طول آبراهه 0/98، مساحت 0/97 و مساحت فرسایش پذیر حوضه 0/95 با بعد فراکتال شبکه زهکشی است و بعد فراکتال شکل حوضه نیز بالاترین همبستگی را با تعداد آبراهه 0/82، مجموع طول آبراهه 0/78 و مساحت 7/0 نشان می دهد (در سطح 0/99). در ادامه با بررسی ویژگی های ژئومورفولوژیک و مقایسه ی آن با بعد فرکتال شکل حوضه و شبکه زهکشی منطقه، وضعیت فرسایشی منطقه ی مورد مطالعه مشخص شد. با توجه به نتایج مشخص شد که واحدهای مستقل مربوط به واحدهای T8، T1 و T6 و در واحد ترکیبی، TO3 دارای بیشترین فرسایش پذیری هستند. این نتایج می تواند در برنامه های کنترل رسوب و آبخیزداری استفاده شود و راهکارهای لازم را برای مدیریت منطقه ارائه دهد. در واقع، پژوهش حاضر نشان داد که تحلیل ابعاد فراکتال می تواند به بررسی سریع و دقیقی از ویژگی های ژئومورفولوژیکی حوضه و شبکه زهکشی منجر شود.

    کلیدواژگان: بعد فراکتال، پارامتر ژئومورفولوژیک، روش شمارش جعبه، مدیریت حوزه آبخیز
  • معین جهان تیغ*، منصور جهان تیغ صفحات 85-104

    هدف از اجرای این پژوهش، بررسی اثر بادهای 120 روزه بر رسوبات جریان های سیلابی وارد شده به منطقه ی سیستان است. با تهیه ی بانک اطلاعاتی از مسیر رودخانه های حوزه های آبخیز بالادست منطقه ی سیستان در کشور افغانستان، مسیر جریان های سیلابی به منطقه مشخص شد و مناطقی که همواره تحت تاثیر این جریان قرار داشت، تعیین شد. پس از جاری شدن سیلاب و خشک شدن آن، در طول بازه ی زمانی 3 سال به صورت تصادفی از رسوبات سیلابی برجای مانده نمونه برداری شد. همچنین با نصب اشل در محدوده های مشخص در دو دوره ی زمانی قبل از شروع وزش بادهای 120 روزه و بعد از آن، ارتفاع رسوبات اندازه گیری شد. در ادامه با دانه بندی 60 نمونه رسوب با استفاده از روش هیدرومتری، پارامترهای آماری میانه (D50)، میانگین (Mz)، کشیدگی (KU)، کج شدگی (SKI) و جورشدگی (σI) تعیین شد. برای تجزیه و تحلیل بادهای منطقه از نرم افزار (WRplot view 8) و برای ترسیم گلماسه های نقاط برداشت نیز از نرم افزار (Sand Rose) استفاده شد. یافته ها نشان داد که میانگین ذرات رسوب، برابر با 88 میکرون و تیپ رسوبی آنها، ماسه ی دانه ریز است. با تعیین آستانه فرسایشی رسوبات جریان های سیلابی و فراوانی بادهای غالب همچنین ترسیم گلماسه ی ایستگاه های مورد مطالعه، یافته ها نشان داد که رسوبات جریان های سیلابی نهشته ی تحت تاثیر وزش بادهای 120 روزه سیستان، قدرت فرسایشی بالایی می یابد؛ به طوری که فراوانی بادهای با بیش از سرعت آستانه فرسایش برای ایستگاه های مورد مطالعه 100 درصد است. در بررسی ارتفاع رسوبات سیلابی نهشته شده، یافته ها بیانگر اختلاف معنی دار در سطح 0/01 (P< 0.01) بین میانگین ارتفاع رسوبات قبل و بعد از وزش بادهای 120 روزه سیستان است. با توجه به آنالیز دانه بندی رسوبات انتقالی با سیلاب، تعیین آستانه فرسایش و توان حمل ذرات به وسیله ی بادهای محلی منطقه و اندازه گیری های میدانی به عمل آمده از ارتفاع رسوبات سیلابی نتیجه گرفته می شود که با شروع وزش بادهای 120 روزه، این رسوبات مهم ترین منبع برداشت است که هر سال همراه با جریان های سیلابی به منطقه ی سیستان وارد می شود و پس از فرسایش، مشکلات زیادی در این منطقه به وجود می آورد.

    کلیدواژگان: دانه بندی، رسوبات سیلابی، سیستان، فرسایش بادی، فرسایش پذیری
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  • Iraj Rahimi, Morteza Seyedian*, Hamed Rouhani, Reza Ahmadi Pages 1-26
    1-Introduction

    Watershed describes an area of land that contains a common set of streams and rivers, which all drain into a single large body of water. For sustainable management of watersheds, soil erosion is a major factor, which accelerates the rate of land degradation and hence influences agricultural productivity, run off movement and sometimes leads flood in the lower basin. Soil is one of the most important elements of natural resources in each country. In areas where erosion is not controlled, soil gradually erodes and loses fertility. There are two methods to maintain soil and prevent erosion: direct method and indirect method. One of the direct methods to prevent erosion is the construction of checking dam. These structures are constructed in floodplains and perpendicular to the flow of reducing water velocity and run off erosion by reducing the bed slope. Check dams are constructed using materials such as wood, stone, rock, and mortar and gravel (gabion). The aim of the present research is to determine the suitable location of mortar and gabion check dam in Ghorchay Ramiyan watershed based on multi-criteria decision-making methods.

    2-Methodology

    Gorkhay basin (one of the sub basins of Gorgan Rood basin) is located in the southern Gorgan Rood basin and in south of the city of Ramiyan, Golestan province. The hydrometric stations of Ramiyan and Nodeh were used for data analysis that located inside and  in the neighbor of study area respectively. Criteria and indicators are chosen for evaluation of topic. The research criteria were also considered as factors influencing the location of check dam construction site in separate clusters for the second layer. The classes or options are classified in the third layer based on the risk classes in a separate cluster. In a hierarchy analysis, the normalization is performed using Saati method on the comparison matrix. In this research, the vector of the weight of the options is calculated using the geometric mean method. Prioritization was done using the AHP model and GIS based on effective criteria such as physiography, hydrology, geology , soil science and socioeconomic factors.

    3-Results

    The weight of socioeconomic, hydrological, physiographic, soil and geological criteria is equal to 0.409, 0.124, 0.0558 and 0.409 respectively, which indicates the impact of criteria on site selecting of gabion and stone-mortar check dam. Based on weights prioritization, priorities 1 to 5 is selected for construction stone-mortar check dam belongs to 14, 10, 13, 6 and 9 sub-basin. Sub-basin No. 14 with a weight of 0.304 is  the first priority and sub-basin No. 1 with weight of 0.129 is the last priority. Among the sub-criteria, the sub- criteria of sensitivity to erosion of geology formation with 0.36 weight has the greatest effect and the sub- criteria of flooding coefficient and slop percent with weight 0.05 have the least effect on the selection of the first priority, that is, sub-basin No. 14. On the basis of prioritization of 62 sub-basins final weights with 2nd grade channel for construction of gobbins, the priorities 1 to 5 belong to the sub-basins 35-35-34-32-57, respectively. Sub-basin No. 36 with a weight of 0.453 as the first priority and sub-basin No. 1 with a weight of 0.113 was proposed as the last priority for construction of gabion.

    4- Discussion & Conclusions

    The rapid growth of technology and economic has transformed human’s life in recent decades and has challenged modern societies with sophisticated decision making. The basic characteristic of such issues is the existence of non-homogeneous and inappropriate criteria or objectives, such as cost, reliability, performance, safety and productivity. Sub-basin No. 14 with weight 0.304 as the first priority (at the end of the basin, which has a slope and high erosion due to formations such as limestone and marn) and sub basin No. 1 is the last priority with weight 0.129 (Shale Formation, Sandstone and coal with high sensitivity to erosion and distance from residential areas and away from resources). Among the sub-criteria, formation erosion sensitivity sub-criteria with weight 0.36 has the greatest effect and the sub-criterion of distance from the road with a weight of 0.01 has the least effect on the selection of the first priority, the sub-basin No. 14. The purpose of this research is to assist managers and decision makers in the Watershed Management Department to select the most appropriate options and to rank the location of structures based on choosing the best decision options and emphasizing on effective decision making by introducing and applying scientific decision-making methods.

    Keywords: Spatial Prioritization, Geographic Information System, Analytical Hierarchy Process, Ghorchay
  • Zahra Yarmoradi, Behrooz Nasiri*, Gholam Hasan Mohammadi, Mostafa Karampoor Pages 27-44
    1-Introduction

    A dust storm is one of the biggest serious environmental problems in the arid and semi-arid regions of the world, causing irreparable damages to farms, facilities, roads, traffic and transportation every year and respitory problems by contaminating the air. Due to the geographic location of Iran which is  in the arid and semi-arid belt of the world, the country is frequently exposed to local and synoptic dust systems. Considering the increasing occurrence of dust in the coming years, drought and climate changes and the emergence of desert zones, the study of this phenomenon is considered important and should be studied by using scientific researches to identify the factors affecting the occurrence of this phenomenon and dust source areas. The main purpose of this research is to identify the sources and also track the dust route entering the east of Iran using the HYSPLIT model, satellite images and synoptic analysis.

    2-Methodology

    In this study, At first, warm season dust storms were studied by using weather data, phenomenal code and horizontal visibility. Then, the storm from August 12 to 14, 2018, was recorded using weather data for East stations and horizontal visibility. For more accuracy, MODIS images of the storm wave on this day were identified and the surface dust concentration was confirmed using the AOD Index. Then, using the European Center for Average Meteorological Data (ECMWF) with a spatial resolution of 0.25 * 0.25, sea level pressure (SLP), temperature, direction and wind speed, and geopotential height At 850, 500 and 250 levels, jet streams were investigated and The synoptic factor of the dust storm was determined. In the next step, using the HYSPLIT model, the path of motion of particles and their source were determined at three levels of 500, 1000 and 1500 meters for 24 hours before the storm. The meteorological data of the model was obtained from a 0.5 degreess GDAS.

    3-Results

    The intensity and extent of the dust storm from August 12 to 14, 2018 showed that its horizontal visibility had been decreased to less than 200 meters across stations in eastern half areas of Iran. On this day, the dry bed of Hamoun, Pozak, Saberi and Hirmand, Afghanistan's plains have been contributed to nourish the storm. The results of synoptic studies showed that when there is a high pressure independent cell in the north-east of Afghanistan and north-east of Iran as well as a low-pressure cell in the southwestern part of Afghanistan, a severe gradient is made between these regions that causes the wind speed at ground level to be more than 14 meters per second. The severe pressure and temperature differences in the region, the lack of humidity and the high radiation angle have drove the dust of deserts outside the northern and eastern borders toward the region, and this area has been under the Azores subtropical high pressure, which its blockage at high levels leads the persistence of dust for three days in eastern Iran. The results of the model also showed that more than 90% of the dust entry routes to the east enters the eastern part of Iran from the deserts of Turkmenistan, Khazakhistan and Afghanistan.

    4- Discussion & Conclusions

    Due to 120-day winds, low humidity, poor vegetation and dry regional substrates, the eastern part of Iran is prone to the frequent occurrence of dusty phenomena. Based on satellite images and AOD index, the storm has formed in the desert region of Turkmenistan and has been expanding to eastern Iran. According to the synoptic study of the warm period of the dust storm in the east, the upper levels of the Iranian plateau are under the control of the Azores high pressure and on the ground surface, the thermal low is also increasing in the eastern half. When two strong low-pressure nuclei with a 990 hp center in southeastern Afghanistan and southeastern Pakistan were deployed so that its tabs penetrated into the studied region and progressed to the Mediterranean, it created the appropriate conditions for climbing a huge amount of dust into the air that in the case of dryness of the area and north-northwestern and northeastern flow of the upper levels, this phenomenon intensified and moved to the eastern part of Iran. At high atmospheric levels, due to air stability and blocking events, as well as air stagnation, the dust is more durable temporally and the process of bringing it down to the ground surface will last longer days. The results of the HYSPLITE modeling output also showed that the source of dust of the eastern half of Iran in the storm studied enter the studied area from the deserts of Turkmenistan and northwest of Afghanistan and Khazakhistan with the north, northwest and northeastern directions up to 90 percent. In all cases, the results of the model are compared with and confirmed by satellite and synoptic studies.

    Keywords: Tracking, Dust, HYSPLI, MODIS
  • Mohammad Poosti* Pages 45-61
    1-Introduction

    Aghajari Formation as the last unit of Fars Group cropps out in Hormuzgan Province with a considerable thickness. This Formtion is composed of red sandstones and green to reddish grey silty marls. According to Kalantari (1992), this formation has the age range of Middle Miocene to Pliocene. The thickness of this formation reaches to 3000m in northern Bandar Abbas (Gholamalian, 2012). The great thickness, broad expansion, slothness (with attention to the calcareaus matrix) and presence of some amounts of Iron rich minerals as grains are charactristics of this formation mineralogical composition. Also, these rocks contain polycrystalline quartz, wavy extinction quartz, fossil fragments and some minor minerals such as moscuvite, chlorite, albite, orthoclase in addition to oligiste. In order to identify the origin of the mentioned minerals; several samples are studied by microscope and Some are processed
    by chemical analysis. In addition, the origin of oligiste particles in was considered; so, some samples containing this mineral were collected from Hormuz Series of Siahoo, Anguran, Zendan and Hormuz salt diapirs.

    2-Methodology

    The studied area is located in 74 km North of Bandar Abbas, near the Siahoo and Aghasin villages. We should Go 64 km northward from Bandar Abbas and then 10 km eastward in order to access the studied section. The studied section is approximately 4 km before the Aghasin village. Fifty samples were collected from Aghajari Formation and Hormuz Series for
     the sake of this study; 22 of them were for chemical analysis and 20 for microscopic thin and polished sections. Three oligiste samples are collected from salt domes for comparison to the Iron rich mineral grains of Aghajari Formation. Oxidic and elemental XRF analysis of samples performed on 22 samples. In addition, point analysis of microprobe exercises are done on the rock forming grains of Aghajari Formation and Hormuz salt plug oligisites with XRF method. Thin and polished sections are studied by polarizan and reflective micoscopes.

    3-Results

    Microscopic investigations on the thin sections of Aghajari Formation Showed the mineralogical content of rocks. Average mineralogical component of grains in this sandstones includs %45 to %50 quartz (%20 wavy extinction quartz and %25 to %30 polycrystalline quartz), less than %10 albite and orthoclase, %3 to %5 black oligiste and %30 to %35 calcareous matrix.
    Quartz is the main mineral in the grains. Polycrystalline and wavy extinction quartzes can generally form in metamorphic phases. On the other hand, angular to semi-rounded quartz Grains show short distance transportation. It seems these quartz grains are originated from the Sanandaj – Sirjan metamorphic belt rocks. Weak mineralogy and grain size sorting and high thickness of Aghajari Formation show fast sedimentation and short distance transportation of grains. On the other hand, comparison of microprobe spot XRF analysis of oligiste grains shows the chemical composition similarity of this mineral in Hormuz series and Aghajari Fomation sandstones. So, these mineral grains are transported from Hormuz series salt plugs to the sedimentary environment during deposition of Aghajari Fomation in the Late Miocene to the Pliocene.

    4- Discussion & Conclusions

    Results of XRF analysis, microprobe and microscopic investigations prove the presence of Fe2O3 as oligiste grains in the Aghajari Formation sandstones. Results of point analysis of these particles are similar to those of Hormuz series; showing the probable origin of oligiste particles in the sandstones. A large amount of quartz is present in the Aghajari Formaion sandstones that cannot be transported from salt plugs, because there are a few amounts of this mineral in the Hormuz Series.
    Wavy extinction quartz grains are abundant in the Aghajari Formation sandstones and have been originated from Sanandaj - Sirjan metamorphic belt.
    Presence of some mineral particles such as: albite, moscuvite, and chlorite in the Aghajari sandstones prove short distance transportation, probably from the Sanandaj - Sirjan metamorphic belt.
    In fact, Aghajari sandstone particles are synchronously transported from two main sources; Sanandaj - Sirjan metamorphic rocks are the origin of quartz grains and oligiste fragments are originated from the Zagros Range salt domes.

    Keywords: Oligiste, Quartz, Aghajari Formation, Hormuz Series, Sanandaj – Sirjan, origin determination
  • Mojdeh Mohammadi Khoshoui*, Mohammad Reza Ekhtesasi Pages 62-84
    1-Introduction

    Different natural phenomena have many variables that make it difficult to find relations among them using common mathematical methods. This problem, along with the impossibility of measuring all elements of nature, has led to a major evolution in the procedure of scrutinizing and explaining. In this way, we can use the fractal geometry with the theory that the order of many natural phenomena is chaotic. Fractal geometry is a quantitative tool for studying the geomorphology of drainage networks and modeling many complex natural phenomena. In fact, geophysical phenomena such as basins are fractal phenomena with fractal behavior. An understanding of geomorphologic characteristics and their performance over basins is very important in the watershed management. This paper focuses on the relationship between fractal dimensions of basin shape and drainage network with the geomorphologic characteristics of basin. Therefore, through an analysis of fractal dimensions and its comparison with geomorphologic characteristics, the fractal behavior of this basin is investigated.

    2-Methodology

    The present study consists of four main sections. The first section is the collection of maps and data. In this section, topographic maps at scale of 1:50000 and geological map at scale of 1:100000 from area were provided. Then, the required layers were extracted from them such as drainage networks and geological units. Sensitivity to erosion of formations was studied in this basin using PSIAC method. In order to investigate more precisely, the Aqda was divided into nine hydrological sub-basins (independent), five non-hydrological sub-basins (dependent) and four hybrid sub-basins. The second section, 18 geomorphologic characteristics were calculated for each sub-basin. In the third section of this study, fractal dimension of drainage networks and basin shape was calculated by box counting method using Fractalyse software in each sub-basin. The focus of the final section is on the relationship between fractal dimensions of basin shape and drainage network with the geomorphologic characteristics of basin.

    3-Results

    The results showed that the T8 and To3 sub-basins, respectively, with values of 1.47 and 1.60 have the highest fractal dimensions of the drainage network. Also, the highest fractal dimensions of the basin shape were obtained with values of 1.05 and 1.08, respectively, in the same sub-basins (T8 and To3). The results also indicated that there were significant relations among the fractal dimensions of the basin shape and the drainage network with geomorphologic characteristics. The highest correlation belongs to the regression relations between the total length of stream, basin area and erodible area with the fractal dimension of the drainage network (0.98, 0.97 and 0.95 respectively). Fractal dimension of the basin shape showed the highest correlation of 0.82 and 0.8 respectively with the number of networks and the total length of stream (significant at 99 percent level). Then, the erodible status in Aqda Basin was determined by studying the geomorphologic characteristics and comparing it with the fractal dimensions of the basin shape and the drainage network. The highest erodible status is in T8, T1, T6 and TO3 sub-basins which should be considered in strategies to manage Aqda basin. In fact, this study showed that fractal dimensions allow a quick and accurate analysis of the geomorphologic characteristics of the basin and the drainage network.

    4- Discussion & Conclusions

    Identification, evaluation and prioritization of different areas can produce valuable information for the watershed comprehensive plans, soil conservation and mitigation of the erosion types based on amount of erosion and sedimentation. For this purpose, the geomorphologic characteristics should be investigated in basins. But extraction of these characteristics and estimation of the erodible status in basins are time-consuming and costly. Therefore, it is very necessary to use an index that has an appropriate estimation of the erodible status in basins. Fractal dimension, with time and cost management, can determine sensitive and high priority basins. With knowledge about the relationship between geomorphologic characteristics basins with fractal dimension, we can predict the other characteristics of basin. The results of this study indicated that there were significant relation between the geomorphic characteristics of sub-basins study and fractal dimension of the basin shape and the drainage network. Other researches on fractal dimension analysis have shown that there is a significant relation between fractal dimension and characteristics such as basin shape, area, branching ratio, drainage density and length ratio of drainage network. But in this study, two characteristics of branching ratio and length ratio of drainage network were not significantly correlated with any of the characteristics and fractal dimensions, and the drainage density was correlated only with frequency rank. Therefore, basins with high erosion will not always have high drainage density. For example, quaternary alluvial deposits have high erosion, but their drainage density is not very high (T4 sub-basin). For this reason, in the future studies, it is better to separate the tectonic streams from the erosion streams. Finally, the results of this study can confirm the findings of other researchers that fractal dimension of drainage network reflects the complexity of the basin shape and can be used as a quantitative index for basin analysis and evolution of the basin.

    Keywords: Box Counting, Fractal Dimension, Geomorphologic characteristics, Watershed management
  • Moien Jahantigh*, Mansour Jahantigh Pages 85-104
     1-Introduction

         The purpose of this research was evaluating the effect of the 120 -day's winds on flood flow entering deposit to Sistan region. At first, it became clear that flood flow path to Sistan area after the floods and droughts, according to the file work is randomly sampled from the flood deposits accumulated for a period of 3 years. Also, high deposit was measured with filed work in two periods before and after the begining of 120-days winds. In order to study the graded sediment samples and granulometry, the parameters were determined middle (D50), Mid-average, Kurtosis, Skewness and sorting. For analyzing the winds of the region WRplot view 8 and the harvest sand rose Software were used. In statistics study parameters of graded flood flow deposit entering to Sistan shows that the average particle size of sediment is 88 microns and mainly were fine-grained sediment. By determining the threshold of peak flow deposits, the frequency of prevailing winds and also draw sand rose of stations points of study, data shows that the high cumulative flow of sediment erosion affected by winds of 120 days of Sistan region. As the frequency of winds over speed ​​threshold is 100 percentages to study station. In study of sediments height, the results showed significant differences at 0.01 levels (p < 0.01) between the heights average of sediment before and after the beginning of 120 days winds in Sistan region. Therefore, according to analyzing Granulometry of Sediments transported by floods, determined threshold and the capability of carrying particles by local winds as well as field measurements, these deposits are the main resources harvested with starting 120- days winds along with flood flows intering Sistan region each year, eroding and causing a lot of problems in that region.
     

    2-Methodology

    In this research we have provided data about the direction of rivers in Afghanistan country watershed. We used accessible images of Google Earth for determining peak flow path in the Sistan area and according to the luck ontinuity of flow in the region, areas that have been affected by flood flow was determined. In the following, it was found rods of Sistan region.  After the floods and droughts, during field operations, accumulated flood sediments samples were collected randomly. Also, the sediment level in scale (Sediments transported by floods and depth of drilled by wind sediments carried by wind) of the 14 points were measured. The above steps have been done during each incoming flow to the Sistan region during 3 years (2016-2018). To evaluate the constituent particles of sediment in granulometry, 60 samples were selected and analyzed in Sistan Agricultural, Natural Resources Research and Education Center lab. In the study of granulometry of sediments taken with respect to deposits collected by 20 sieves. The estimation depth of accumulated flood sediments for two stages before and after the 120-day winds flood in summer. Selected by accumulated flood sediments and high measured sediments. In order to study the graded sediment samples and granulometry, parameters were determined middle (D50), Mid-average, Kurtosis, Skewness and sorting. For winds of region analysis, we used WRplot view 8 and the harvest sand rose Software. In statistics study parameters of graded flood flow deposit entering to Sistan shows that the average particle size of sediment is 88 microns and mainly were fine-grained sediment.

    3-Results

    By determining the sediment in granulometry, frequency curve of particle was drowning for each of the study samples. Drawing on sediment size distribution for each sample, the results of the study analysis parameters, were estimated the peak flow of sediment into the Sistan region. Based on the results, the median and mean values ​​of accumulated sediment on the bed river (Sistan River) and Hamon wetland were phi 6.2 and 6.4, respectively. Changes in these parameters are almost identical, but in some areas, the median value is greater than the average value which is due to finer grain particles. The general trend changes two parameters; the mean and median separable in study terms. In the first year, medians index was more than the average value of the samples taken which indicates that the presence of fine particles is more than coarse particles percent (the average size of silt). Whereas in the second year, the average of sediment samples taken increased the size of the fine silt particles coarser grain and reduced the fine silt particles in much finer grain. In the third year, the mean and median values ​​are almost identical and fine silt was deposited as sediment size. The result shows that the tilting parameter values of sediment samples of peak flow was from very good tilting (0.22) until very weak tilting (2.86). Study of parameter values ​​tilting this parameter indicates the rate of change between 0.14-0.76.

    4- Discussion & Conclusions

    In this study, for the first time has survey graded sediment input peak flow in Sistan. Then determine particle size and analyze the wind of the region, was estimated attrition of the sediments. In examining sediment samples in granulometry, during study period and the overall changes under the influence of mean and median and existence fine and coarse particles was perceptible in the overall trend analysis of these two parameters. Fluctuations in hydrological and hydraulic conditions prevailing in the bed of peak flow to Sistan area includes Sistan and Frahe rivers are determining particle transport in flood deposits. In support of this important Morphometry properties including sorting that reflects that the energy levels in sedimentary environments and energy situation is stable over time shows that the natural sediment sorting peak flow is not formed under the influence of hydraulic and dynamic conditions governing the flow of the river. In the other hand, because the rivers are seasonal and alluvial transmitter rivers transfer flood flows in the Sistan region, decrease the sediments have been sorted turbulent flow conditions along the river and rapid changes in river flow and erosion phenomenon over time. The results showed that sediment in granulometry of sediments transported during peak flow is always fine which has a low threshold velocity and due to the frequency and intensity of wind in the region, this has eroded sediments which effects of like phenomena dust and endangering the health of residents. Therefore, according to the analysis in granulometry of sediments transported by the floods and determined threshold, capability of carrying particles by local winds and field measurement, these deposits are the main sources of harvest starting with 120 days winds.

    Keywords: Aggregation, Flood sediments, Sistan, Wind erosion, Erodibility