per
انجمن ایرانی ژئومورفولوژی
پژوهشهای ژئومورفولوژی کمّی
22519424
2018-11-18
1
1
1
18
77862
ارزیابی شاخص های مورفودینامیک تپّه های برخانی (مطالعهی موردی: ریگ چاه جام)
The Investigation of Morphodynamic Indices of Barchan Dunes (Case Study: Chah Jam Erg)
عبدا.. سیف
1
سیّد حجّت موسوی
2
دانشگاه اصفهان
دانشگاه اصفهان
چکیده
مخاطرات محیطی و بههدر رفتن منابع طبیعی، ازجمله علل ایجاد راهکارهای مدیریت بحرانهای زیستمحیطی هستند. یکی از مهمترین چالشهای محیطی نواحی جنوبی کویر حاج علی قلی، هجوم ماسههای روان در قالب تپّههای برخانی به مراکز سکونتی، راه های ارتباطی و تأسیسات زیربنایی است. برخان ها بر اساس ویژگی های باد غالب منطقه و قابلیّت اندک دسترسی به ماسه نشئت می گیرند که هلالی شکل بوده و از ماسهی روان تشکیل شدهاند. هدف از این پژوهش، ارزیابی شاخصهای مورفودینامیک تپّههای برخانی ریگ چاهجام با کمک روشهای تجربی، ریاضی و آماری است. برای این کار، نخست برای تعریف شاخص پایداری چشمانداز برخان، میزان شار ماسه در محدوده ای مشخّص به ابعاد ارتفاع و عرض برخان با استفاده از معادلههای تجربی مورد بررسی قرار گرفت. سپس برای تبیین شاخص پایایی، مهمترین شاخصهای مورفومتری 15 برخان بهروش نمونهبرداری طولی اندازه گیری شد و با تحلیل آنها از راه آزمون های آماری، به رابطهسنجی و ارزیابی مدل پایایی اقدام شد. نتایج حاکی از تبیین مدلهای پایداری و پایایی سامانه برخان است. مدل پایداری دربردارندهی میزان ورود و خروج انرژی و مادّه به درون چشمانداز برخان بوده که در نتیجهی این فرآیند، یک ساختار جریانی شکل میگیرد. ساختار جریانی نیز بیان کنندهی تعادل و پایداری چشمانداز برخان در طول زمان است. همچنین نتایج حاصل از بررسی مدل پایایی نشان میدهد که گروه برخانهایی با مقدار جابهجایی سالانهی بیشتر از 12 متر با داشتن حدّاکثر تعداد و بالاترین میزان جابهجایی، کمترین پایایی را دارند. بنابراین نیازمند بیشترین توجّه و ضرورتهای برنامهریزی برای تثبیت ماسههای روان و مدیریت محیطی برخانهای رونده هستند.
Extended Abstract
Introduction
The environmental issues and loss of natural resources are the important causes of management strategies creation of the environment crisis. The influx of quicksand to settlements, communication ways and economical installations in the form of barchan dunes, is one of the most important of environmental problems in the South of Haj Ali Gholi playa. Barchan dunes originate from the characteristics of prevailing wind and little ability to access the sand that is crescentic shape, and have been formed from mobile sand.
A side view of a barchan shows a rather flat aerodynamic structure. When viewed from above, a barchan presents a crescentic shape with two horns pointing downwind. A sharp edge divides the dune in two areas: the windward side and the slip face. Because of a boundary layer separation along this sharp edge, a large eddy develops downwind and wind speed decreases dramatically. Therefore, the incoming blown sand is dropped close to the brink line.
The aim of this study is the assessment of morphodynamic indices of barchan dunes in Chah Jam Erg using experimental, mathematical and statistical methods. By obtained results, we can comprehend a correct understanding from 3D morphology and morphodynamic characteristics of barchan dunes and their behaviors, to manage the environment of desert regions using systemic approaches.
Methodology
The study field is located in south of Haj Ali Gholi playa, central IRAN. Haj Ali Gholi playa situated in southwestern of Shahroud city to south of Damghan city. Chah Jam Erg, with an area of about 25260 hectares, is one of the most important ergs of Haj Ali Gholi playa that is located asymmetrically along northeastern - southwestern edge of the playa with a length of 10 to 12 Km. The study area is located at latitudes between 35° 45΄ and 35° 50΄ North, and at longitudes between 54° 40΄ and 55° 10΄ East.
First, the study area was investigated by satellite images of Google Earth and 1:50000 maps. Then, for explanation of steady state index, the most important morphometric parameters of 15 barchans were measured by linear sampling in the studied field, and the relation study of between parameters and the evaluation of the steady state model were performed using analysis of them by statistical tests.
In context of defining the stability index of Barchan system, the rate of sand flux was investigated using empirical equations in the given extent with dimensions of Barchan height and width.
Results and Discussion
In the study area, we can see various barchans, most of them having same and similar shapes. Generally, the barchans of this region have a height of 2.1 to 17.9 meters, a length of 19.5 to 307.85 meters and a width of 6.3 to 165.6 meters.
When system maintains its life and function and has a maximum efficiency, there is the stability in the landscape. Until the needed energy of landscape maintain was supplied, and the flow of material balance occurs in the system, it remains stable. In this study, for exploration of stability index of the barchan, the method of sand flux calculation is used. So that, first, the input flux (qi) and output (qo) of barchan system was calculated using the relations (1) to (7). Then, using the proportions between input flux (qi) and output flux (qo), the occurrence probability of the three states was recognized in barchan system as defined in following:
1) , in other words, the input flux is the equal with output flux. Thus, the barchan system is the stable.
2) , in other words, the input flux is more than output flux. Thus, the barchan system is the unstable with developing trend.
3) , in other words, the input flux is less than output flux. Thus, the barchan system is the unstable with vanishing trend.
The results obtained relation study, show that relationships between movement rates and morphological parameters are following from simple linear, power and exponential equations. The relationships between barchan morphometric parameters represents a maximum significant exponential reverse relationships between movement rate and barchans height parameter with R square of 0.915 and Std error of estimate of 0.133.
To define the steady state index, the annual displacement rate of 15 barchans was divided into 5 groups according to comparison test. Also, a zero amount that is presenting the absolute steady state was added to the previous groups. A total, the steady state index includes the 6 groups in studied barchan dunes. Then, the steady state index of each barchan dune is determined by the groubs. The results show that group 6, with annual displacement rate more than 12 meters, have the maximum number and highest rates of displacement, and have the lowest steady state.
Conclusion
The base of applied geomorphology analysis is according to systemic approach. Systemic geomorphology is based on recognition of geomorphic forms and processes and relationships among them. Efficiency of this stand point, when there are linear and nonlinear reciprocal relationships between parts and elements of system, is very important.
The morphology of barchan system reflects the dynamic sets of processes that their goal is the formation of barchan landscape. Development and evolution of Barchan system is the function of various feedbacks between forms and processes. These feedbacks lead to structural changes in the flow of matter and energy in barchan system. In other words, the structural and functional interaction of form and process will be developed barchan system.
The results show the exploration of stability and steady state models for studied barchan dunes. The stability model was involving the input and output of energy and material in the barchan system that eventually is formed a flow structure. This structure is representing the stability and equilibrium of barchan system in time. Also, the obtained results from investigation of steady state index show the barchan dunes, with annual displacement rate more than 12 meters, have the maximum number and highest rates of displacement, and have the lowest steady state. Thus this group is demanding the more attention and planning requirements for stabilization of quicksand and environmental management of mobile barchan dunes.
Keywords: Barchan, Morphodynamic, Stability index, Steady state index, Chah Jam Erg.
https://www.geomorphologyjournal.ir/article_77862_88248a78a77f31c22ea8d61b9738671b.pdf
برخان
مورفودینامیک
شاخص پایداری
شاخص پایایی
ریگ چاهجام
Keywords: Barchan
Morphodynamic
Stability index
Steady state index
Chah Jam Erg
per
انجمن ایرانی ژئومورفولوژی
پژوهشهای ژئومورفولوژی کمّی
22519424
2018-11-18
1
1
19
32
77863
پهنهبندی تحوّل و حسّاسیت کارست با استفاده از مدل رگرسیون خطّی چندمتغیّره در منطقهی کارستی شاهو
Zoning of Karst Evolution and Vulnerability, Using Multiple Linear Regression Model in the Shaho Area
محمّدصدیق قربانی
1
محمّد اونق
2
دانشگاه پیام نور
دانشگاه بنارس هندوستان
چکیده
فرایند تحوّل کارست، فرایندی پیچیده و متأثّر از متغیّرهای مختلف است. با توجّه به حسّاسیت ذاتی سیستم کارست، امروزه در برنامهریزیهای مربوط به مناطق کارستی تلاش بر این است که میزان تحوّل و حسّاسیت کارست در چهارچوب مدل یا مدلهایی مناسب مورد بررسی قرار گیرد. در این مطالعه منطقهی کارستی شاهو، بهعنوان منطقهی شاخص کارستی در زاگرس شمالغربی برای پهنهبندی تحوّل و حسّاسیت کارست با استفاده از مدل رگرسیون خطّی چندمتغیّره مورد بررسی قرار گرفته است. لایههای اطلاعاتی و نقشههای رستری تهیّه شده در محیط (GIS) شامل سنگشناسی، میزان فاصله از گسل، شیب، ارتفاع و جهت دامنه، بهعنوان متغیّرهای مستقل (پیشگوییکننده) و لایهی اطلاعاتی فروچالهها بهعنوان متغیّر وابسته، پس از پردازشهای لازم نرمافزاری وارد مدل رگرسیونی چندمتغیّره شدهاند. نتایج حاصل از معادلهی رگرسیونی یا بهگفتهای، نتیجهی حاصل از تأثیر دادن ضرایب رگرسیونی متغیّرها در ماتریس دادهها بر اساس روابطی (استعداد وقوع فروچالهها)، بهصورت طیفی از اعداد مثبت و منفی درآمده است. اعداد مثبت بیانگر وجود شرایط لازم برای توسعهی کارست و اعداد منفی بیانگر نبودن شرایط مناسب برای توسعهی کارست است. دامنهی این طیف عددی، بهصورت کیفی به پنج کلاس از استعداد بسیار زیاد تا بسیار کم تقسیم شده است و در قالب جدول و نقشهی استعداد توسعهی کارست برای منطقه مطالعاتی ارائه شده است. درنهایت، بر اساس نقشههای استعداد توسعهی کارست، نقشهی حسّاسیت کارست در سه کلاس حسّاسیت زیاد، حسّاسیت متوسّط و حسّاسیت کم ارائه شده است. همخوانی بالای نقشهها و نتایج حاصله با واقعیّت منطقهی مورد مطالعه، گویای کارایی و قابلیّت اعتماد مدل است.
Extended Abstract
Introduction
Large areas of the ice-free continental area of the Earth are underlain by karst developed on carbonate rocks and roughly 20–25% of the global population depends largely or entirely on groundwaters obtained from them (Ford & Williams, 2007, 1). So that karst system has a critical role on the development of human communities all around the world. karst evolution is a complicated process and relates to numerous factors such as lithology, hydrology, hydrogeology and etc. Karst resources have widespread scientific, cultural and economic values. In developing countries, human activities threat these valuable and non renewable resources seriously. Nowadays decision makers in their plans for karstic areas in order to protect these valuable resources, regarding the intrinsic vulnerability of karst systems, attempt to propose methods and models for determine the degree of karstification and its sensitivities. Regional assessment of karst system vulnerability especially in the watersheds is a useful tool for management and protection of karstic areas and helps local authorities and decision makers to choose best policies to use karst recourses. In this paper a well known karstic area, called Shaho in the NW Zagros, using a multiple linear regression model has been studied for evaluating its vulnerability and design vulnerability maps.
Methodology
In this research, firstly, we designed the karst geomorphology map of the area using topographic maps (1:50000), aerial photographs (1:55000), IRS panchromatic image at 5 meter resolution. The position of sinkholes and shafts were mapped mainly in the filed works. Then for our purpose using GIS tools, Slope, aspect and elevation maps were derived from topographic maps. Lithology and liniment maps were prepared in the same way from geology maps (1:100000). For designing and overlaying maps, we used Ilwis 3.3 and Arc View 3.1softwares. Statistical analysis was done by Spss 11.5.
Then GIS-based raster maps including lithology, distance from faults, slope, aspects and elevation as independent variables and the sinkhole and shaft's map(geomorphology) as independent factor (predictive factors) were entered in the multiple linear regression model.
Results and Discussion
GIS-based maps and data sets related to variables (distance from faults, slope, aspects, and elevation) all were converted to raster maps. Lithology and geomorphology maps as quality maps by a different process were converted to raster maps. Lithology map by applying weighs (1-5) in which 1 belonged to less effective formation and 5 belonged to most effective formation, was converted to a raster map. The geomorphology map was rasterized by converting it to 0, 1 map which 0 was related to the non karstic parts and 1 was related to karstic parts. The number of records was taking into account in the linear regression equation for all maps equally were 12783 records. Results obtained from regression equation or in the other phrase, multiplying the impact factor of regression coefficients by the data matrixes resulted in a range of positive and negative figures. Positive figures relate to the parts of the area that are well karstified or are capable for karstification and negative figures are vice versa. In fact, overlaying kart geomorphology map of the area with the derived map from regression model show that the results of the model are reliable. Because the pattern of positive figures mostly cover the distribution of sinkhole and shafts. The derived map from linear regression model (karst capability map), that shows the karstic parts and predict the capable parts for karst development was classified into five classes (very high, high, moderate, low, very low) which very high refers to the parts of the area that have well developed surface karsts or are very capable for karst development and very low refers to the non karstic parts or parts of very low capability for karstification. In the vulnerability point of view areas with high rates of karsification are very sensitive for contaminant infiltrations and human interference. Finally the vulnerability map was derived from primary map (capability map) and classified into three high, moderate and low classes and symbolized with colors. High class with blue color refers to the very sensitive parts and low class with yellow color refers to the parts with the low sensitivities.
Conclusion
The results obtained from linear regression model including tables and maps especially vulnerability map, are highly correspond to the real conditions of Shaho karstlands and express the more reliability of multiple linear regression model. According to our vulnerability classifications (high, moderate and low) and assessment of the human impacts, karst system in this area is seriously under threat. About 23% of the area has been located at the high sensitivity class, 26.34% at moderate sensitivity class and 50.65% at low sensitivity class. Obviously any unplanned activities including quarrying, construction of roads and buildings, irregular livestock grazing and recreational activities inside the high and moderate classes can make damages and seriously affect the karst system. In this area mostly the catchments of karstic springs that have a well developed surface karst, correspond to the high sensitivity class and high permeability as well. Thus in these parts disposal of waste and contaminants resulting from human activities can put groundwater resources at risk. In order to reduce the human impacts and protect the karst sources in this area local authorities and decision maker should pay proper attention to them.
https://www.geomorphologyjournal.ir/article_77863_cbecdf75714dab5f5bdf32b1fbb3206d.pdf
شاهو
کارست
فروچاله
مدل رگرسیونی
پهنهبندی
Shaho
karst
Sinkhole
Regression Model
Zoning
per
انجمن ایرانی ژئومورفولوژی
پژوهشهای ژئومورفولوژی کمّی
22519424
2018-11-18
1
1
33
46
77864
تحلیل وضعیّت پایداری مجرای رودخانهی قزل اوزن با استفاده از روشهای تنش برشی، شاخص مقاومت نسبی بستر و مطالعات صحرایی
Analysis of the Stability of River Channels Using Methods of Bed Shear Stress and the Relative Strength Index (Ranging Between 30 km Miyaneh City to the Zanjan Political Boundaries)
محمّدحسین رضایی مقدّم
1
محمّدرضا ثروتی
2
صیّاد اصغری سراسکانرود
3
دانشگاه تبریز
دانشگاه شهید بهشتی
دانشگاه تبریز
چکیده ناپایداری مجرای رودخانه، نقش بهسزایی در ایجاد فرسایش، تخریب سواحل و تأسیسات کنارهی رودخانه دارد. این نقش بهویژه هنگامی تشدید میشود که مجرا و بستر رودخانه آبرفتی باشد. رودخانهی قزل اوزن یکی از مهمترین رودخانههای ایران است. این رودخانه اثریافته از عوامل مختلفی چون، زمینشناسی منطقه، ویژگیهای تشکیلات آبرفتی و شرایط هیدرولیکی جریان، رفتار مورفولوژیکی پویایی دارد. هدف این پژوهش، بررسی وضعیّت پایداری رودخانه با استفاده از روشهای تجربی و ریاضی و مقایسهی نتایج این روشها با نتایج مطالعات صحرایی و ویژگیهای مورفولوژیک هر کدام از بازههای مورد مطالعه در طبیعت است. برای رسیدن به این هدف، در این پژوهش با استفاده از روشهای تنش برشی و شاخص مقاومت نسبی بستر، وضعیّت پایداری رودخانه تحلیل و سپس نتایج روشهای گفتهشده با مطالعات و اندازهگیریهای صحرایی مقایسه شدند. نتایج نشان داد که در بازهی اوّل محدودهی مورد مطالعه، نتایج روشهای تجربی با مطالعات صحرایی همخوانی دارد؛ ولی در بازههای دوم و سوم نتایج روشهای تجربی با مطالعات صحرایی همخوانی ندارد. این بررسی نشان داد که روشهای تنش برشی و شاخص مقاومت نسبی بستر، تنها در مجراهای آبرفتی اهمّیّت داشته و به نتایج آنها میتوان استناد کرد. بهکارگیری این روشها در بازهای غیرآبرفتی، نتایج غیرواقعی و دور از انتظار خواهد داشت و با ویژگیهای مورفولوژیک رودخانهی مورد مطالعه همخوانی نخواهد داشت.
Extended Abstract
Introduction
Instability of the river channel has significant role in creating erosion, degradation of coastal and Facilities around the river. This role will be intensified especially when the channel of river bed is alluvial. By monitoring changes in river morphology and specific measures can be prevented from the occurrence of Instability River. The purpose of this study is investigation the stability of the river, using experimental and mathematical methods and comparing the results of these methods with results of field studies and morphological characteristics of each interval in nature. In this research, the study area is Qezel Ozan River in longitudes 47 48' to 48 27' and latitudes 37 12′ to 37 25′. In this study for the separation of mountain and plain intervals, the studied route was divided into three periods.
Methodology
At first the studied area was investigated by Topographic maps 1:50000, geological maps 1:100000 and satellite images IRS 2007 to check the status of the stability river in the studied intervals and plan map of the river were obtained from satellite images. Then, during the field Performed sampling of the sides and bed materials the river for determine particles size River and River depth was measured. Particles size of the bed sediments and its sides was performed using standard methods Ashto 80-77. To calculate the return periods of flood flow used from distribution of Gambl. The total shear stress and critical stress was calculated using the relationship Swami and Mital.
Results and Discussion
This study showed that the methods of bed shear stress and the relative strength were significant only in alluvial channels and results are reliable. Results using these techniques in non-alluvial intervals will be unrealistic and unexpected and will not match with morphological characteristics of the river. Therefore first interval as the combination of arterial and Meandering River in alluvial river bed is unstable interval and Second and third interval Introduced As the stable interval that river has been limited by Rock bed and sides.
Conclusion
Comparing the existing stresses and critical stress indicated that in the all studied stations the shear stress was greater than the critical stress and so these areas are unstable. Based on this index, highly erosion and low shear strength in the studied stations have been caused increasing of changes studied intervals. Also investigation of RBS index showed that this index is less than unite in all stations so theirs are unstable. Survey of results of field studies, topographic maps and satellite images showed that the results of experimental methods in the second interval and very little for the third interval is different. The results of mentioned methods are quite consistent with the characteristics of the first interval that is due to morphological characteristics studied intervals.
https://www.geomorphologyjournal.ir/article_77864_807b5909e5b0ead43a8fc73b92c16b49.pdf
ناپایداری مجرا
روشهای تنش برشی
شاخص مقاومت نسبی بستر
رودخانهی قزل اوزن
Channel Instability
Shear Stress Methods
The Relative Strength Index
Qezel Ouzan River
per
انجمن ایرانی ژئومورفولوژی
پژوهشهای ژئومورفولوژی کمّی
22519424
2018-11-18
1
1
47
58
77865
پهنهبندی مناطق متأثّر از خطر زمینلغزش در جادّهی تبریز ـ مرند با استفاده از سنجش از دور و GIS
Landslide Hazard Zonation in the Tabriz-Marand Road Using RS and GIS
شهرام روستایی
roostaei@tabrizu.ac.ir
1
حسن احمدزاده
2
دانشگاه تبریز
دانشگاه تبریز
چکیده
جادّهی تبریز ـ مرند یکی از شریانهای مهمّ ارتباطی کشور است که افزونبر ارتباطات داخلی، برای ارتباطات برونمرزی نیز اهمّیّت زیادی دارد. این جادّه که روی سازندهای سست و نیمهسست کواترنری واقع شده است، هرازچندگاهی لغزش زمین را تجربه میکند. هدف این مقاله، شناسایی پهنههای در معرض لغزش است که با بهکارگیری دادههای مختلفی همچون لیتولوژی، شیب دامنهها، کاربری اراضی، پوشش زمین، فاصله از عوارض خطّی (جادّه، رودخانه و گسل) و همپوشانی آنها، مخاطرات طبیعی تهدیدکنندهی حریم اتوبان و خطّ ریلی تبریز ـ مرند را با تأکید بر زمینلغزش و با بهرهگیری از قابلیّتهای سنجش از دور و سیستم اطلاعات جغرافیایی (GIS) مورد بررسی و ارزیابی قرار میدهد. نتایج ارزیابی نشان داد که ساختار خاصّ زمینشناختی، شرایط اقلیم محلّی و نیز تراکم نهشتههای کواترنری (در هر دو طرف جادّه) در کنار عامل گرادیان شیب، از عوامل اصلی بروز زمینلغزش است که ساختوسازهای انسانی آن را تشدید میکند. همچنین مشخّص شد که مناطق قرار گرفته در پهنه با خطر بالا، منطبق بر مناطقی است که در آنها زمینلغزش رخ داده است.
Extended Abstract
Introduction
Tabriz-Marand road is one of the important connecting networks in Iran which is not only significant inner and communications but also in abroad relations. This road rests on loose Quaternary formations and sometimes experiences landslides. The aim of this paper is to identify areas which are susceptible to slides. This paper evaluated the natural disasters that are threatening the confine of Tabriz-Marand road and railway, with the use of different data such as lithology, the slope of foothills, land use, land cover, the distance from linear features (road, river, and fault) and overlaying of them, with the emphasis on landslides and using remote sensing and GIS capabilities.
Methodology
My study area has been selected between Tabriz- Marand approximately 65 km length and 5 km wide in east Azarbayjan province that the main road and railway rests in this limit and the Tabriz- Bazargan highway is under construction. In this research, used the topography maps in 1:25000 scale, geology maps in 1:100000 scale, SPOT-5 satellite images with 10 meters spatial resolution, climatology data from Tabriz and Marand station and GPS. The overlaying and weighed methods were used for analyzing data.
Results and Discussion
The evaluations showed that in study area, the height deference is 1000 meters, and 20 percent of area has slope between 20-60 persent. It is also recognized that more landslides occurred between 1600-1900 meters height and 25-60 percent of slope range.
Furthermore, it is recognized that average annual precipitation in Tabriz station is 327 mm and in Marand station is 243.4 mm that 40.6 percent of this, occurred in spring and caused slope instability. The northern fault of Tabriz as a main individual tectonic feature that determinately continues to- Moro and Misho mountains, on the side of Quaternary loose formations accounted for a trigger in slope movement's occurrence. According to the NDVI produced from SPOT image, the vegetation index of study area determinate between -0.96 to +0.96.
The region between Sofeyan and Marand due to southern steepness slope that connecting to stream network and main road, being unstable because of spring and winter precipitations. Force of gravity is main factor to occur mass movement and falling weathered materials in this region. Feet cutting due to road and railway passes from hill slope feet and along the river, and seasonal flooding accelerated route instability.
Conclusion
In this paper, the road between Tabriz - Marand Was studied using topography and geology maps, climatologic dada, satellite images and the overlaying and weighed methods. 13.6 percent of this section is unstable that placed around of main road and Yam village. The results showed that the specific geological formation, the regional climate conditions and the density of quaternary deposits on the sides of the road along with the factor of slope gradient are among the factors that cause mass movements which are intensified by human construction activities. It was also determined that the parts located in areas with higher danger are in coincidence with areas where landslides had taken place.
https://www.geomorphologyjournal.ir/article_77865_6ce1e0f84f73589d33f3ff6d850bfdcc.pdf
مخاطرات طبیعی
زمینلغزش
زمینشناسی
جادّهی تبریز ـ مرند
سنجش از دور و GIS
natural hazard
Landslides
Geology
Tabriz-Marand Road
Remote Sensing and GIS
per
انجمن ایرانی ژئومورفولوژی
پژوهشهای ژئومورفولوژی کمّی
22519424
2018-11-18
1
1
59
68
77866
بررسی خطر سیلخیزی در زیرحوضه های استان آذربایجانغربی
The Study of Flood Risk in Western Azerbaijan Province Sub-basins Using GIS
منوچهر فرج زاده اصل
1
دانشگاه تربیت مدرس
چکیده
سیل از پدیدههای مخرّب طبیعی است. بهطورکلّی، سیلخیزی، وضعیّت سیلاب در آن حوضه را مشخّص میکند. عوامل بسیاری در بروز سیلابهای کشور نقش دارند که از آن میان میتوان به رخداد بارشهای شدید، ذوبّ ناگهانی برف در منطقهی کوهستانی و عملکرد همزمان هر دو عامل اشاره کرد. منطقهی یک حوضهی آبریز، بهسبب وجود شرایط طبیعی مختلف، از پتانسیل رخداد متفاوتی برخوردار است. طبقهبندی و اولویتبندی زیرحوضهها، گام اول را برای مقابله یا کاهش اثرهای سیلاب در حوضههای آبریز برعهده دارد. بر همین اساس، هدف از مطالعهی پیش رو، تبیین وضعیّت سیلاب در زیرحوضههای استان آذربایجانغربی است. در همین راستا، خسارات و خطرات سیل بر اساس آمار و اطلاعات ثبت شده در گذشته تحلیل شده است. برای استخراج دقیق محدودهی سیلخیزی با استفاده از روش استراهلر به طبقهبندی رودخانههای استان پرداخته شد. سپس با استفاده از این طبقهبندی برای هر یک طبقهها، یک پهنه بهعنوان محدودهی خطر سیل در محیط GIS تعیین شد، در ادامه با استفاده از نقشههای 100000/1 زمین شناسی، واحد تشکیلات کواترنری( Qal) به این محدوده افزوده شد. در گام بعد برای اینکه شدّت خطر سیلپذیری در زیرحوضههای استان مشخّص شود، از آمار وقوع سیل در زیرحوضههای استان استفاده شد و درنهایت، شدّت خطرپذیری سیل در زیرحوضههای استان بهدست آمد. نتایج بهدست آمده نشان میدهد که زیرحوضهی زنگمار در خطر سیلپذیری شدید قرار دارد و لازم است تا تدابیری برای کاهش آثار سیل در این منطقه انجام گیرد.
Extended Abstract
Introduction
Flood is one of complex and destroyed phenomenon. Generally flood risk determines flood situations in each basin. Iran country have a arid climate that rainfall with high density is the main climatic features and caused many floods with destruction human, buildings and engineers structures. The object of this study is the analysis of flood situations in sub-basins of westerns Azerbaijan province. To do this statistics of flood hazards and destruction analyzed.
Methodology
Westerns Azerbaijan province located in the north west of Iran and have a temperate climate with rainy season in winter and autumn. Data used in this study are lithology, slope gradient, thickness of materials, humidity coefficient and rainfall rate, temperature, land use. Other data were used is
Satellite data including ETM images of 2005 studied and using color composite images of 7, 4 and 1 bands recognized. Then in order to flood susceptibility areas take places with high accuracy, Straher method for river classification were used. Using this classification for each of these classes, one area titled hazard flood area calculated in GIS environment and finally Qal geology formation added this area from geology map scaled 1:100000. In next step in order to calculation of flood intensity used historical flood records.
Results and Discussion
The result indicated that Zangbar sub-basins have high flood hazards and need required works to mitigate floods impacts. The prepared map show Simineh Rud and Zarineh Rud subbasins have high intensity and Simineh rod have high flood areas. In generally the analysis shows 3033 residential centre and 36 urban areas located in studied province that 603 residential and 10 urban areas were located in flooded zones. The western subbasins with 125 residential centers have highest number of located in flooded areas.
Conclusion
Consider to location of western n Azerbaijan and due to high latitude and high elevation have high rate of snow. In addition spring season rainfall increase and caused flood occurrence. In totally all subbasins have flood susceptibility areas with low and high intensity. Then in order to combat with flood hazards in these areas is vital and different methods can be used.
https://www.geomorphologyjournal.ir/article_77866_a93219734f8dd5f333b83f42f2f048e5.pdf
خطرپذیری سیل
آذربایجانغربی
شدّت سیل خیزی
GIS
Flood Risk
Western Azerbaijan
Flood Intensity
Remote Sensing
GIS
per
انجمن ایرانی ژئومورفولوژی
پژوهشهای ژئومورفولوژی کمّی
22519424
2018-11-18
1
1
69
81
77867
مورفودینامیک ساحلی و نقش آن در تحوّل سدهای ساحلی دلتای رود جگین
Coastal Morphodynamic Processes and Its Role in the Evolution of Coastal Barriers in Jegin River Delta
مجتبی یمانی
myamani@ut.ac.ir
1
سمیّه عمادالدّین
2
قاسم لرستانی
3
دانشگاه تهران
دانشگاه تهران
دانشگاه تهران
چکیده
سواحل محلِّ تلاقی محیطهای آبی و خشکی بوده و از این دو تأثیر میپذیرند. متغیّرهای گوناگونی مانند ویژگیهای زمینشناسی، اقلیمی، زیستی و حرکات آب دریا، عوامل شکلزای اصلی بهشمار آمده و لندفرمهای گوناگونی را ایجاد میکنند. در این پژوهش، فرایندهای هیدرودینامیکی خشکی و دریایی تأثیرگذار در پیدایش لندفرمهای خطّ ساحلی قاعدهی دلتای رودخانهی جگین، در شرق بندرگاه جاسک مورد بررسی قرار گرفته است. برای بررسی دقیقتر نیز، روی فرایندهای تشکیل و تحوّل سدهای ساحلی این دلتا تأکید شده است. تصاویر ماهوارهی لندست، نقشهها و نرمافزارها، ابزارهای اصلی پژوهش را تشکیل دادهاند. تصاویر ماهوارهای در نرمافزار ENVI تحلیل شده و همچنین برای تلفیق دادهها و تحلیل مقایسهای آنها، نقشهها و دادهها در نرمافزارهای Arc GIS و Freehand ترسیم و تطبیق داده شدهاند. روش کار، مقایسهی تغییرات سدهای ساحلی در یک دورهی 33 ساله بهوسیلهی تصاویر ماهوارهای و عکسهای هوایی با استفاده از نرمافزارهای مذکور و نیز کنترل میدانی بوده است. هدف اصلی، تعیین میزان تغییرات در بازهی زمانی یاد شده و بررسی نقش عوامل هیدرودینامیک دریا و خشکی در روند این تغییرات بوده است. نتایج نشان میدهند که حجم چشمگیری از رسوبهای وارد شده توسّط رودخانهی جگین به محدودهی خطّ ساحلی، تحت تأثیر امواج غالب جنوبشرقی، در امتداد خطّ ساحلی بهسمت غرب توزیع شده و تحت تأثیر آن سدهای ساحلی و تالابهای جزرومدّی شکل گرفتهاند. مقایسهی زمانی تغییرات نشان میدهد که سدهای ساحلی در بخش شرقی دلتا حجیمتر بوده و تغییرات وسعت و ابعاد آنها، در درجهی اوّل تابع تغییر مسیر دورهای رودخانهی جگین در سطح دلتا و سپس راستای امواج غالب است. بیشترین میزان تغییرات طیّ دورهی زمانی مورد مطالعه، مربوط به سدهای ساحلی بخش شرقی دلتاست که دامنه آن گاهی به بیش از 400 متر میرسد.
Extended Abstract
Introduction
The coasts are concourse water and land environments that they are influenced from both. The main morphogenesis factors are Include Variety of variables such as geological characteristics, climatic, biological and water sea movements that create Varity of landforms. In this study, has been examined the hydrodynamic processes in land and sea that were affective in the appearance coastline landforms in below of the Jegin River delta in the east harbor Jask. For closer examination, has been emphasized on the formation and evolution processes in coastal bars of Jegin River Delta. Jegin river delta is the largest delta in coastal plain of Western Makran and Hormozgan province. The area spanning latitude 25° 30´ to25° 40´ N and 58° 5´ to58° 30´ E. it has 23.7 km long.
Methodology
For analysis of Temporal and spatial variations Jegin River has been used Land Sat satellite images, (The MSS sensor in October 1975 with bands 1 to 4, The TM images in June 1987 with bands 1 to 7, The ETM images in April 2001 and May 2005 with bands 1 to 7) and also aerial photographs from 1961 and 1983 has been used.
Gabrik and Yekdar topography maps with 1:50000 scale for base maps and Gabrik geology map with 1:10000 scale for Separation Old Jegin river terraces has been used. The images were processed in ENVI software. And changes in area and dimension of coastal bars have been extracted to timing maps.
For analysis tidal range has been used of daily tides Statistics from 2000 to 2010 in National Cartographic Center. To examine the effects of wind in sand transport direction in surface of coastal bars, Seasonal wind roses in WERPLOT view software has been drawn and their relationships with formation of coastal bars in region has been studied.
Eventually, all of the dates have been transferred on the base maps and have been delineate and adapted in the software ArcGIS and Freehand
Method of study was comparison of changes in coastal bars through a period of 33 years of satellite images and aerial photographs using the above soft wares and field control.
Results and Discussion
Effective variables in formation coastal bars Jegin River are mainly influenced by hydrodynamic processes of the sea (waves, tidal and coastal currents) and Jegin River hydrodynamic in delta surface of land. The erodiblility of Ophiolite complex formation Makran and river flooding are the origin large volumes of sediments transfer to the sea. Sedimentary material is transported by water network and finally, the distribution of sediment along the coastline with interaction other environmental factors lead to the formation of coastal bars.
The waves and tidal currents are the most important marine hydrodynamic processes which in creation of coastline Landforms are distinct than other factors. Deposits are transferred to the coastline by Dora waves and are collided With the Southeast part of delta coast and are distributed along the coastline.
Miles Collision Create the Currents along coastline that Causes sediments move toward the West. Finally function of tidal and coastal currents create by waves, density of silt - sand particles, are formed coastal bars in below of the Jegin River delta.
Conclusion
The results show that significant volume of sediments into coastline by Jegin River is distributed along the coastline toward the west, affected by waves with southwest direction and formed coast bars and tidal lagoon. Time comparison of changes show that the coastal bars been more massive in the eastern part of the coastal delta and changes in area and dimension are function of periodical track change in Jegin river delta firstly and direction of dominant wave secondly. The most change during the period studied is related to the coastal bars in the eastern part of Jegin River delta that it sometimes reaches to 400 meters.
https://www.geomorphologyjournal.ir/article_77867_27a0a4e5a53455f83af357a68de1608b.pdf
سدّ ساحلی
دینامیک دریا
دلتای جگین
ژئومورفولوژی
ساحل
Coastal bars
Sea dynamic
Jegin delta
geomorphology
Coast
per
انجمن ایرانی ژئومورفولوژی
پژوهشهای ژئومورفولوژی کمّی
22519424
2018-11-18
1
1
83
104
77868
هیدرولوژی سیلابهای قدیمی با استفاده از رسوبات آب راکد (مطالعهی موردی: رودخانهی درونگر خراسان)
The Study of Paleoflood Hydrology Using Slack-water Deposits (Case Study: Darungar Basin)
سیّدرضا حسینزاده
srhosseinzadeh@um.ac.ir
1
مهناز جهادی طرقی
2
دانشیار ژئومورفولوژی گروه جغرافیا، دانشگاه فردوسی مشهد
استادیار دانشگاه پیام نور
چکیده هیدرولوژی پالئوسیلاب که شاخهای از ژئومورفولوژی رودخانهای و مبتنی بر ژئومورفولوژی تاریخی است، سیلابهای قدیمی یعنی سیلابهایی که با ایستگاههای دبیسنجی یا مشاهدههای مستقیم انسان ثبت نشدهاند را مطالعه میکند. در این شاخهی علمی از شواهد بسیاری برای تشخیص سیلابها استفاده میشود که یکی از مهمترین آنها رسوبهای آب راکد است. این مطالعه به کشف و تحلیل چینهشناسی نمونههایی از این رسوبها در بخشی از حوضهی آبریز رودخانهی درونگر و همچنین بازسازی جریانهای سیلابی قدیمی در سایتهای مربوطه میپردازد. در این پژوهش نخست با بازدیدهای میدانی دقیق، سایتهای رسوبات آب راکد مورد شناسایی قرار گرفته و پس از تحلیل چینهشناسی در محل، نمونههایی از رسوب برای مطالعهی دقیقتر به آزمایشگاه انتقال داده شده است. برای برآورد سطح سیلابها با توجّه به ارتفاع رسوبات آب راکد، پس از نقشهبرداری تفصیلیِ مقاطعِ عرضی و طولی کانال رود در سایتهای نمونه، دبی سیلابها با استفاده از فرمولهای رایج مدلسازی شده است. نتایج نشان میدهد که در سایتهای نمونه، تعداد 10 تا 20 سیلاب قدیمی تشخیص داده شده که دبی اوج آنها از 112 تا 519 مترمکعّب در ثانیه تغییر میکرده است. این نتایج با برآوردهای انجام شده به روشهای مرسوم هیدرولوژی اختلاف چشمگیری را نشان میدهد.
Extended AbstractIntroductionPalaeoflood hydrology is the reconstruction of the magnitude and frequency of recent, past, or ancient floods using geological evidences (Baker et al., 2002). The term "palaeo" has contributed to the general misconception that palaeoflood techniques are only used for estimating very old floods over geological timescales. However, most palaeoflood studies involve the study of the last 5000 years with an emphasis on the last millennium, or even the last100 years in ungauged basins (Benito et al., 2005).J. Harlem Bretz (Bretz, 1929) was the first scientist to use geological evidence intensively to elucidate information about past floods during his studies of the pathways followed by the cataclysmic outburst floods from Pleistocene Lake Missoula. However, the term and concepts of palaeoflood hydrology were formally introduced by Kochel and Baker (1982). They emphasized on slack-water deposits (SWD) and palaeostage indicators (PSI) as geological, geomorphological and geobotanical evidences for reconstruction of ancient floods. These indicators represent the high stage of the flood and provide the best natural record of large flood magnitude. Slak-water deposit sites include back-flooded tributary mouths, caves and alcoves in canyon walls, channel expansions where flow separation causes eddies, and overbank floodplain deposits. Ideal palaeoflood sites preserve multiple flood stratigraphic records, which can be separated into individual flow events using sedimentological criteria (Baker, 1987 Benito et al., 2003).Over the last 20 years, palaeoflood hydrology has achieved recognition as an interdisciplinary branch of geomorphology and hydrology. In addition it has seen major advances, which can be partly explained by the interest generated by global climate change and its effect on river system dynamics. Several studies, in fact, deal with the chronology of ancient floods with respect to climate changes over the past millennia, thus allowing for a better understanding of flood phenomena while taking into account changing climate environments (Laurent, 2004). Unfortunately, palaeoflood hydrology has been not interested in Iran however it is an emergence science for this country. Occurrence of 3 catastrophic floods in the Madarsoo River during 2001 to 2004 and incapability of traditional hydrologic methods to estimate of peak flood discharges, caused the authors considered to necessary of palaeoflood hydrology as a way to understanding of flood phenomena in the country (Hosseinzadeh et al., 2006 Hosseinzadeh, 2008). This paper deals with the using of slack-water sediments and hydraulic calculations for the reconstruction of the high-magnitude flood records at 3 sites in a small sub-basin upstream of Daroongar River over the last centuries. The basin area with 80 km2 is located in the northeastern of Iran across the border between Iran and Turkmenistan. At three study sites the river is confined by bedrock walls, as the river cuts west-east through the Cretaceous thick layers limestone of TIRGAN in the kopet Dagh Mountain. The river channel is a deep bedrock canyon, although at the wider gorge bends gravel bars occur. In the case of the Daroongar River the protected sites mainly include caves and alcoves in the canyon walls. Three main flood deposit sites were studied along the Shamkhal canyon. The bedrock canyon allows the assumption that little to no change in the shape of the canyon throughout the late Holocene occurred.MethodologyThe main objectives of this paper are: (1) reconstruction of the catalogue of major flood events using the stratigraphic record of slackwater flood deposits, (2) study of palaeoflood hydraulics associated with these floods with estimation of flood peak discharges, (3) analysis of palaeoclimatic conditions related to the palaeoflood periods derived from stratigraphic data. primary study to finding of slackwater deposits was using the aerial photographs with 1:20000 scale and satellite Images from google earth website. Then we walked through the canyon to mark the favorite slackwater deposit sites for further studies. In the next step, 3 sites were selected at the beginning of the canyon and filed works concentrated on these sites to detailed study of sedimentology, stratigraphy and channel geometry. During the period October 1-3, 2010 the flood deposit profiles were exposed by digging and cutting. This enabled a visible exposure of the entire section of the SWD relic from top to bottom, as well as correlation between sedimentary units. The sequence of deposits exposed in each profile was separated into flood deposits associated with flood events using well-established sedimentological criteria (Baker, 1987 Benito et al., 2003) (Figs. 7, 8). This sedimentological separation enabled the reconstruction of the stratigraphy at each site. Each unit of the deposits at each site was documented in detail and sampled for optional future laboratory analyses. The height of slack-water sediments in the selected sites can be extrapolated to the mainstream for a conservative estimate of peak paleoflood stage. Once peak flood depth is known, the slope-area method [Dalrymple and Benson, 1967] can be used to indirectly estimate paleoflood discharge. Field data necessary for slope-area calculations include flood depth, channel cross sections (Figure 5), estimates of floodplain and channel roughness, and estimates of water surface slope. Paleoflood discharges computed using the modified Manning equation:(Where is roughness A., is cross-sectional area (m2),R is the hydraulic radius, and S is the water surface slope. Roughness estimates varied between 0.035 and 0.04, near the values reported for bedrock streams of 0.04 to 0.05[Chow, 1959].Channel bed slope was substituted for S hence the values are probably low. The height of slack-water sediments in the selected sites can be extrapolated to the mainstream for a conservative estimate of peak paleoflood stage. Once peak flood depth is known, the slope-area method can be used to indirectly estimate paleoflood discharge. Field data necessary for slope-area calculations include flood depth, channel cross sections estimates of floodplain and channel roughness, and estimates of water surface slope.The survey used a total station with a laser rangefinder to form a series of 10 cross-sections every 40 m in average along the study segment of the upper Shamkhal canyon. The measurements include all geometric parameters of the channel and the entire canyon of the, such as width, depth, present bed river, and gradient hydraulic parameters, such as roughness coefficient, and sinuosity and the elevations and locations of all PSIs, such as driftwood lines, SWDs. Results and Discussion Site 1This site is an alcove at the left bank of river in the beginning of shamkhal canyon. four depositional sequences were found at this site which included 20 flood depositional units. these sequences are separated by none-flood stratums which characterized by human activities or extreme bio-turbation . These flood units consist of 50-60 percent silt, 20-30 percent fine to medium sand and about 20 percent clay. Sediments featuring mainly diffused lamination flow structures. The contacts usually consist of mud cracks, clay accumulations and charcoal or organic materials.Site 2This site is been formed in the end of river bend at the top part of an alluvial terrace approximately 3 m above the bed river of the Daroongar. Depositional units were found at this site, 12 of which correspond to flood deposits. The flood deposits consist of fine and medium to coarse sand, featuring diffused lamination, with many charcoal pieces mixtures with some units. The highest layer of slackwater deposits had been covered by paleosoils, rock debris and slop-wash materials. The contact lines are characterized by color and grain size changes.Site 3This site is an alcove in the steep-side gorge which is originated by faulting activity. Four depositional units were found at this site, two of which corresponds to flood deposits. The flood units consist of coarse sand to silt, featuring diffused lamination and bio-turbation. Slope-area calculations at the site indicate that the peak discharge reconstructed for floods associated with deposits at the top of site 1 is about 350 m^3/s -1 and about 340 m^3/s -1 for the top of site 2. Calculated peak paleovelocities for these floods are between 5 and 6, respectively. Peak discharge calculations after 20% increases the flood surface on the top of slack-water deposits resulted up to 500 m^3/s in both sites. Based on another flood mark on the steep-side canyon walls, peak flood discharge is been estimated about 700 m^3/s.ConclusionPaleoflood hydrology is an important topic in fluvial geomorphology, which is an emergence science for estimation of large flood magnitude and frequencies in Iran. The results of this paper shows existence of large errors in peak discharge calculations when the traditional methods is been used. The peak discharge in the Daroongar gage station has been recorded 202 m^3/s for an area with 942 Km^2, developed for study area about 65 m^3/s based regional analysis and SCS methods. We estimated the peak discharges about 350 m^3/s based on slack-water deposit hights and more than 500 m^3/s with using other paleostage indicators. Using the paleflood methods in the large rivers of Iran can improves the predicting of peak discharge methods. Duo of short period records in the gage stations, paleoflood methods will be demonstrate confident results for flood risk assessment and environment planning projects.
https://www.geomorphologyjournal.ir/article_77868_a437320f42a9dd6df9c5f1e6ccdf9532.pdf
پالئوهیدرولوژی
پالئوسیلاب
رسوبات آب راکد
بازسازی پالئودبیها
رودخانهی درونگر
کانیون شمخال
Paleohydrology
Paleoflood
Slack-water Deposits
Paleodischarge
Daroongar River
Shamkhal Canyon