فهرست مطالب

پژوهش های فرسایش محیطی - سال هشتم شماره 2 (پیاپی 30، تابستان 1397)

فصلنامه پژوهش های فرسایش محیطی
سال هشتم شماره 2 (پیاپی 30، تابستان 1397)

  • تاریخ انتشار: 1397/06/13
  • تعداد عناوین: 6
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  • کیانوش بهرهی، غلامعباس صیاد، احمد لندی* ، حمیدرضا پیروان صفحات 1-22
    پژوهش حاضر به منظور بررسی نوع کاربری اراضی و اثر طبقات شیب بر رسوب تولید شده، با استفاده از شبیه ساز باران در حوزه ی آبخیز کاکاشرف از سرشاخه های حوضه ی آبخیز کرخه در استان لرستان انجام گرفت. دستگاه شبیه ساز باران مورد استفاده، از نوع باران ساز غیر فشاری از جنس پلکسی گلاس بود. واحد های کاری نیز بر اساس نقشه ی کاربری اراضی و توپوگرافی منطقه انتخاب شد. بر این اساس، در شش واحد کاری (زیرحوضه) با سه نوع کاربری جنگل، مرتع و زراعت و در سه طبقه شیب 10، 20 و 30 درصد و در طی 93 مورد، آزمایش شبیه ساز باران با شدت بارش موثر بر فرسایش با ویژگی حداکثر شدت بارندگی ده ساله با تداوم 30 دقیقه ای برابر 36 میلی متر در ساعت، ایجاد و مقدار رسوب اندازه گیری شد. حداکثر شدت بارندگی ده ساله با تداوم 30 دقیقه ای درحوزه ی آبخیر مورد مطالعه 36 میلی متر بود و برای تجزیه و تحلیل آماری از نرم افزار SAS استفاده شد. با توجه به نتایج به دست آمده، میانگین مقدار رسوب در طبقات شیب 10، 20 و 30 درصد به ترتیب برابر 49/7، 41/23 و 06/61 گرم و میانگین رسوب در سه کاربری جنگل، مرتع و زراعت به ترتیب 07/46، 88/30 و 02/15 گرم در واحد سطح پلات دستگاه باران ساز برابر 1 متر مربع برآورد شد. بنابراین، در شیب30 درصد و کاربری جنگل بیشترین مقدار رسوب تولید شد که علت آن از یک سو به وزن پایین تر خاک های جنگل مرتبط است و از سوی دیگر، به تخریب خاکدانه ها در اثر بهره برداری بیش حد. نتایج تجزیه ی واریانس نشان داد که بین کاربری های مختلف تحت بررسی در زیر حوضه های مختلف، از نظر رسوب تولید شده تفاوت معنی دار در سطح پنج درصد وجود داشت. همچنین اثر متقابل زیر حوضه × نوع کاربری اراضی از نظر مقدار رسوب، در سطح یک درصد معنی دار بود. نتایج مقایسه ی میانگین آزمون دانکن نشان داد که بین مقدار رسوب و طبقات شیب و بین سه کاربری جنگل، مرتع و زراعت از نظر مقدار رسوب تفاوت معنی دار در سطح یک درصد وجود داشت و با افزایش شیب از 10 به 30 درصد، مقدار رسوب تولید شده افزایش یافت. نتایج ماتریس همبستگی نشان داد که بین پارامتر های خاک و مقدار رسوب همبستگی معنی دار وجود ندارد.
    کلیدواژگان: آزمون دانکن، توپوگرافی، تخریب جنگل، فرسایش خاک، رواناب
  • محسن آرمین* ، معصومه بازگیر، سیدعلی صالح ولایتی نژاد صفحات 23-41
    بررسی دستور العمل های طراحی سدهای کوتاه نشان می دهد که معمولا موضوع تولید رسوب و اثر رسوب گذاری آینده بر عمر سد و ذخیره ی آب در آن قابل توجه نیست و اغلب بر طراحی مهندسی عمران و جنبه های سازه ای آن توجه می شود. عملیات احداث سد مخزنی در خروجی حوزه ی آبخیز کوه برد با مساحت 29/38 کیلومتر مربع در استان کهگیلویه و بویراحمد، از سال 1390 شروع شده است. حوزه ی آبخیز کوه برد یکی از حوزه های آبخیز بدون آمار رسوب است که استفاده از مدل های تجربی برآورد رسوب در آن الزامی به نظر می رسد تا داده های حاصل شده، مبنایی برای برنامه ریزی های مدیریتی در حوضه ی سد باشد. هدف از تحقیق حاضر، برآورد تولید رسوب حوزه ی آبخیز کوه برد با استفاده از یک مدل تجربی ویژه، همچنین ارزیابی فنی سد در حال احداث در خروجی حوضه با استفاده از یک سری شاخص های ساده است که در مناطق مختلف دنیا توسعه یافته اند. در این تحقیق با استفاده از نقشه های پایه و اطلاعات بررسی های صحرایی، امتیاز 3 عامل موثر بر میزان تولید رسوب در مدل تجربی مذکور در قسمت های همگن حوضه تعیین و کل حوضه میانگین گیری وزنی شد. سپس با قرار دادن امتیازهای به دست آمده در رابطه ی مدل، میزان تولید رسوب برآورد شد. نتایج نشان داد میزان رسوب تولیدی در حوضه ی سد کوه برد 13/8 تن بر هکتار در سال است که با احتساب نسبت تحویل رسوب 18/0، میزان فرسایش خاک حوضه معادل 16/45 تن بر هکتار در سال است. پیش بینی می شود که بعد از 20 سال (عمر مفید سد) ، حدود 27 درصد از ظرفیت ذخیره ی اولیه ی سد از دست برود. نتایج این تحقیق برای برنامه ریزی اقدامات اصلاحی در زمینه ی حفاظت خاک در سطح حوزه ی آبخیز و کاهش حجم رسوبات ورودی به مخزن سد و در نتیجه افزایش عمر آن مفید خواهد بود.
    کلیدواژگان: ظرفیت سد، فرسایش خاک، نوع و زهکشی خاک، وضعیت پوشش گیاهی
  • ابراهیم اصغری کلجاهی* ، خانم سکینه حسین پور اصل کلیبر، عطاالله ندیری صفحات 42-61
    دریاچه ی ارومیه یکی از بزرگترین دریاچه های آب شور جهان است که در حال خشک شدن می باشد. یکی از نگرانی هایی که در این باره وجود دارد، انتشار ریزگردهای نمکی از پهنه های خشک شده ی این دریاچه به وسیله ی باد است. در این راستا، به بررسی پتانسیل ایجاد گرد و غبار نمکی در پهنه ی شمال شرقی دریاچه ارومیه که نزدیک ترین پهنه به شهر تبریز محسوب می شود پرداخته شده است. براساس بررسی عکس های ماهواره ای، بازدیدهای محلی و با توجه به جنس رسوبات، این پهنه به 4 زیرپهنه تفکیک شده است. این چهار زیرپهنه به ترتیب از سمت خشکی به دریاچه، زیرپهنه ی خاک طبیعی، خاک نمک دار، سنگ نمک خاک دار و سنگ نمک خالص نامگذاری شده که مساحت هر کدام به ترتیب 160، 220، 170 و 58 کیلومتر مربع است. برای بررسی موضوع، ابتدا بر اساس آمار و اطلاعات موجود به بررسی شرایط اقلیمی پرداخته و گلباد منطقه تهیه شد. جهت غالب بادهای منطقه به سمت شرق و شمال شرقی است. با نمونه برداری از زیرپهنه های مختلف و آزمایش های فیزیکی و مدل سازی و آزمایش های تونل باد، مدول فرسایش بادی رسوبات در ساحل شمال جزیره ی اسلامی، 1157 گرم بر متر مربع و مدول فرسایش بادی رسوبات ساحل شرفخانه، 1948 گرم بر متر مربع در دقیقه تعیین شده است. برای پهنه های نمکی هر دو منطقه مدول، فرسایش بادی خیلی کم (با امکان فرسایش ناچیز) حاصل شد. در زیرپهنه های نمک خالص و نمک خاک دار که نمک به صورت متبلور و سنگ نمک دیده می شود احتمال ایجاد گرد و غبار نمکی خیلی کم است، اما در زیرپهنه ی خاک نمک دار به خصوص در سواحل جزیره ی اسلامی، پتانسیل ایجاد گرد و غبار نمکی کم و بیش وجود دارد. مساحت این زیرپهنه حدود 35 درصد پهنه ی مورد مطالعه است. در مجموع بر خلاف ارزیابی های اولیه، خوشبختانه پتانسیل ایجاد گرد و غبار نمکی در این پهنه اندک است.
    کلیدواژگان: تونل باد، دریاچه ی ارومیه، ریزگرد، فرسایش بادی، نمک
  • عقیل مددی، ایمانعلی بلواسی* صفحات 62-83
    فرسایش یکی از مهم ترین عوامل موثر در هدر رفت منابع ارضی است. آگاهی از میزان خطر فرسایش، امکان شناسایی نواحی بحرانی و اولویت بندی برنامه های مدیریتی و حفاظتی را فراهم می سازد. هدف از این پژوهش، ارزیابی خطر فرسایش خاک با استفاده از مدل منطق فازی، فناوری سنجش از دور و سیستم اطلاعات جغرافیایی در حوضه ی آبریز سیمره چنار است. بدین منظور، ابتدا داده های 7 پارامتر تاثیرگذار در فرسایش خاک شامل شیب، جهت شیب، لیتولوژی، کاربری اراضی، بارش، خاک و آبراهه در محیط GIS آماده شد. برای تهیه ی نقشه ی خطر فرسایش با مدل منطق فازی از اپراتورهای عملگر اجتماع فازی (Fuzzy OR) ، اشتراک فازی (Fuzzy AND) ، ضرب جبری فازی (Fuzzy Algebraic Product) ، جمع جبری فازی (Fuzzy Algebraic Sum) و گاما فازی (Fuzzy Gamma) استفاده شد. برای ارزیابی و اعتبارسنجی نتایج حاصل از عملگرهای مدل منطق فازی، طی بررسی میدانی موقعیت 90 نقطه از نقاط دارای فرسایش با استفاده از دستگاه GPS مشخص و این نقاط با نقشه ی نهایی فرسایش انطباق داده شد. ارزیابی نتایج به دست آمده از ضریب آماری کاپا نشان می دهد که عملگر گامای فازی 9/0 با ضریب کاپای 83/0، در پهنه بندی خطر فرسایش خاک در حوضه ی آبریز سیمره چنار دقت بسیار خوبی دارد. بر اساس پهنه بندی صورت گرفته با استفاده از عملگر گاما فازی 9/0، به ترتیب 59/16، 37/31، 72/27، 98/17 و 34/6 درصد از مساحت منطقه در کلاس های فرسایش خیلی کم، کم، متوسط، زیاد و خیلی زیاد قرار گرفته است.
    کلیدواژگان: سنجش از دور و سیستم اطلاعات جغرافیایی، حوضه ی آبریز سیمره چنار، فرسایش، مدل منطق فازی
  • شیرین محمدخان* ، انور مرادی، فاطمه مرادی پور صفحات 84-103
    فرآیندهای رودخانه ای و بادی از عوامل مهم تغییر مورفولوژی در سطح زمین است. هنگامی که رودخانه ها و تپه های ماسه ای باهم برخورد می کنند، اثر انتقال رسوب بین دو سیستم می تواند به تغییر در یک یا هر دو سیستم منجر شود. با توجه به اینکه سطح گسترده ای از ایران تحت تاثیر فرسایش بادی و رودخانه ای است، بررسی اثر متقابل این دو فرآیند در راستای اهداف مدیریت یکپارچه ی سیستم های رودخانه ای و بادی بسیار پر اهمیت است. روش اجرای این تحقیق، توصیفی- تحلیلی است. در این پژوهش برای اولین بار در کشور، 304 سایت که در آنها رودخانه ها و تپه های ماسه ای با هم تلاقی دارند، با استفاده از تصاویر ماهواره ای، شناسایی و تجزیه و تحلیل شد. در هر سایت ویژگی های کلیدی مانند جهت رودخانه، جهت انتقال ماسه، زاویه ی تلاقی رودخانه ای - بادی، نوع تپه های ماسه ای و الگوی کانال رودخانه، مشخص و روابط بین هر یک از عوامل بررسی شد. براساس این داده ها، شش نوع مختلف از اثرات متقابل طبقه بندی می شود که تغییرات بین سیستم های رودخانه ای و بادی را منعکس می کند. نتایج تحقیق نشان داد که بین نوع زاویه ی برخورد و نوع تپه ماسه ای، زاویه ی برخورد و نوع اثر متقابل، و الگوی کانال و نوع اثر متقابل، ارتباط معنی داری وجود دارد. این روابط نشان داد که الگوی کانال های رودخانه ای فعال، بیشترین مکان هایی هستند که سیستم های رودخانه ای یا بادی بر یکدیگر غالب می شوند، اما تعادل بین آنها پایدار نیست. همچنین بین تپه های ماسه ای و الگوهای کانال هیچ ارتباطی وجود نداشت. با این وجود، تحقیقات بیشتری در کشور لازم است تا چگونگی تاثیر فرآیندهای رودخانه ای و بادی را بر همدیگر و تغییرات ژئومورفولوژیک ناشی از آنها بررسی کند.
    کلیدواژگان: اثرمتقابل رودخانه ای- بادی، تپه ماسه ای، رودخانه، ژئومورفولوژی، جهت باد
  • محمد علی فخاری، مجید لطفعلیان، سید عطاالله حسینی* ، عبدالواحد خالدی درویشان صفحات 104-118
    احداث جاده های جنگلی در مناطق مرطوب، مهم ترین عامل ناپایداری دامنه های شیب دار است. مواد افزودنی و اصلاحکننده ی متنوعی با هدف حفظ آب و خاک در جهان استفاده می شود که در این میان، نقش مواد اصلاحی آلی قابل دسترس و دوستدار محیطزیست بیشتر قابل توجه قرار گرفتهاست. در این پژوهش کارایی دو نوع مالچ طبیعی خرده چوب و کاه و کلش برنج بر مقدار رواناب، رسوب و استقرار نهال های کاشته شده ی توسکا قشلاقی و بید جنگلی در دامنه ی خاکریزی جاده جنگلی در مقایسه با تیمار شاهد ارزیابی شد. تعداد 27 کرت با ابعاد 2×4 متر، در سه تکرار و در دامنه ی خاکریزی جاده جنگلی احداث شد. رطوبت خاک، درصد پوشش علفی، رویش قطر یقه و ارتفاع نهال، رواناب و رسوب کرت برای 12 ماه (2/1394 لغایت 2/1395) در مقیاس رگبار برای 28 رویداد بارندگی طبیعی برداشت شد. نتایج نشان داد که خرده چوب بیشترین اثر را در کاهش حجم رواناب و جرم رسوب به ترتیب به میزان 01/54 و 07/73 درصد داشت. کاه و کلش و خرده چوب، غلظت رسوب را به ترتیب 87/23 و 61/11 درصد کاهش داد. نتایج پایش رطوبت در عمق 2 سانتی متری خاک نشان داد که کاه وکلش با 23/22% (01/0P ≤) بیشترین تاثیر را در حفظ رطوبت خاک برعهده داشت، بیشترین (48%) و کمترین (36%) پوشش علفی نیز به ترتیب در تیمار شاهد و کاه و کلش مشاهده شد. کاه و کلش بیشترین اثر را در افزایش رویش قطر یقه نهال ها به میزان 84/39 درصد و رویش ارتفاع آنها به میزان 51/4 درصد برعهده داشت. میانگین رویش قطر یقه و ارتفاع گونه توسکا به طور معنی داری بیش از بید بود. نتایج پژوهش حاضر نشان داد که ژئوتکستایل های طبیعی اثر معنی داری (05/0P ≤) در کاهش میزان رواناب و رسوب داشت؛ بنابراین می توان با استفاده از آنها، به استقرار نهال و کاهش میزان فرسایش خاک در دامنه های فرسایشی و شیب دار جاده های جنگلی کمک کرد.
    کلیدواژگان: حفاظت خاک، رواناب، رسوب، زیست مهندسی، مالچ طبیعی
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  • Kianoush Behrahi , Gholam Abbas Sayyad , Ahmad Landi*, Hamidreza Payrowan Pages 1-22
    Introduction
    The present study was performed to investigate the effects of slope percentage and land use type on the produced sediment by an artificial rainfall simulator in Kakasharaf watershed, a branch of Karkhe watershed (Lorestan province).
    Methodology
    The rainfall simulator used in this research was designed and constructed by the Soil Conservation and Watershed Management Institute. This device is a portable non-pressurized piston gun with the dimensions of 119.5 × 83 cm and a height of 1.60 m. The rainfall simulator was calibrated and adjusted to the location of the test based on the maximum rainfall intensity of 30 minutes. In order to select the location of the test, after designing the units, land use, and mapping of the slopes of the studied basin, six sub-basins with the three types of forest, pasture and agriculture were selected. After collecting and recording the data, SAS and Excel softwares were used for statistical analysis and plotting. One-way analysis of variance and comparison of means were done based on Duncan test at 1% level.Results 
    The average of sediment yield obtained from rainfall simulator in three slope classes and three land uses in sub-basins of the study area showed that in three different land uses, by increasing slope percentage, the amount of sediment yield increased. This trend was not observed in the forest and agricultural land uses in sub-basins 2 and 4, and the amount of sediment yield did not correlate with the increase in slope percentage. The reason for this can be attributed to the effect of some soil characteristics such as the percentage of lime, organic matter, clay content, soil nitrogen and pH of these hill slopes. The amount of sediment yield in different sub-basins, i.e. in rangeland uses in basin of six with a mean sediment of 95.9, and in sub basin five with a mean sediment of 95.75 g in the plot, respectively, had the highest and lowest amount of sediment in pasture land uses. In agricultural land use, the highest sediment yield measured in sub-basin 2 indicated an average of 85.86g and the lowest sediment in the sub-basin showed a mean sediment of 33.31 in the plot area. Also, in 5th basin with a sediment of 1.444 g and in the sixth basin with a mean sediment of 32.27 g, the highest and lowest amount of sediment was produced on the plot area and in the forest land uses. In general, the average sediment yields from the rain fall simulator in the entire Kakashpour area at 10, 20 and 30 percent slopes were 7.49, 23.41 and 61.66 grams, respectively. By increasing the amount of slope percentage, the amount of sediment yield increased as well. The average amounts of sediment at the plot area in the forest, pasture and agriculture were 46.07, 30.88 and 15.02, respectively.Discussion &
    Conclusions
    The results showed that the average quantities of sediment resulted from the plot area with one square meter of rainfall simulator in Kakasharaf watershed were obtained as 7.49, 23.41 and 61.06 g in the slope degrees of 10, 20 and 30%, respectively, and 46.07, 30.88 and 15.02 g in the three land use types of forest, pasture and agriculture, respectively. Therefore, the highest sediment quantity was produced in the slope degree of 30% and forest land use due to the mature forest soils exposed to erosion because of the destruction of forest soils by farmers. Analysis of variance showed a significant difference (p<0.05) between the different sub-basins from the viewpoint of the produced sediment. Also, the interaction effect between sub-basin and land use type on the produced sediment indicated a significant difference at 0.01. Also, the results of Duncan`s mean comparison test indicated a significant difference between the land slope degrees and also between three land use types of pasture, forest and agriculture in terms of the produced sediment and the sediment increased significantly with an increase in the slope  rate from 10% to 30%. Based on the results of the Pearson correlation matrix, soil properties did not have a meaningful correlation with soil loss. The results of sediment yield in different uses indicated that the highest amount of sediment was in the forest and the lowest amount referred to the agricultural land. The reason of this result could be the activity of microorganisms and earthworms that increase porosity and organic matter, and lower specific gravity of soil particles that are more easily displaced by runoff. Also, the soil of forest land use in this area has become dense and hardened due to the easy access of the people of the area, and the continuous cutting of trees. In agricultural lands due to the use of organic fertilizers and the presence of straw after harvesting (which can increase organic matter) as well as the continuous tillage operations in soil, soil permeability can increase. Therefore, the amount of sediment yield was higher in rangelands and forests due to the excessive grazing and the frequent transportation of livestock and, consequently, a decrease in the permeability rate of the soil. The results also showed that the increase in the slope amounts would trigger the sediment yield increase as well. The reason is its effect on the speed of runoff and partly due to the intensification of the effects of rain drops (Toy et al., 2002). Their results showed that the effect of slope percentage on runoff and sediment was significant. Slope amount had a positive effect on the amount of separation of soil particles due to the impact of rain drops.The results of the analysis of variance and the comparison of the mean of the sediment yield in the six sub-basins showed that there is a significant difference between the sediment yields of the sub-basins at the 5% level. The reason for this difference can be attributed to various conditions such as topography of the area, geology, soil characteristics, land use in each sub-basin, as well as the impact of human and managerial factors in the sub-basins, which ultimately affect the amount of sediment produced in the six sub-basins.
    Keywords: Duncan test, forest Destruction, Runoff, Soil erosion, Topography
  • Mohsen Armin*, Masoumeh Bazgir , Sayed Alisaleh Velayatinejad Pages 23-41
    Koohbord dam watershed with a total area of 38.29 square kilometers in Kohgiluyeh and Boyerahmad province is one of the watersheds without sedimentation data, which requires the use of empirical models to estimate the sediment for estimating sediment, so the results obtained through data is the basis of the management plans of dam watershed. In this research, using base maps and field data, the score three factors affecting the amount of sediment yield were determined using a special empirical model of the dam watershed in the homogeneous parts of the watershed and weighed for the whole watershed and by estimating the obtained scores in the model relationship, sediment yield was estimated. The results showed that the amount of sediment yield in the Koohbord dam watershed is 13.8 tons per hectare per year, taking into the account of sediment delivery proportion of 0.18, which is equivalent to 45.16 tons per hectare per year for soil erosion. It is estimated that after 20 years lifetime of the dam, about 27% of the initial capacity of dam’s storage is lost. Meanwhile, due to the evaporation, about 32% of dam’s volume is lost too.
    Introduction: There are strong links between the availability of water for agricultures and livestock productions, and the incomes for poor rural nation. Rainfall variations, particularly droughts, effect on their living as well One meaning of increasing people’s resilience to these shocks is to store water in dams – so that crops can be irrigated and cattle watered during dry seasons. Many of the small dams are constructed in semi-arid regions of Africa which is rapidly filled with sediments and sometimes only after a few years. When dams silt up the rural areas that is relied on them for cattle watering or small-scale irrigations that deprived of the water and food security that dams provide them, and their source of income is seriously affected too. Predicting soil erosions, sediment yields and dam sedimentation rates can be a complex task, it requires professional experts, and in generally it has poorly covered in small dam design manuals. These results in many small dams constructed with little or no consideration of the impact of future siltation of a dam’s life or on water yields. This issue is poorly covered in most small dam design manuals, which mostly focuses on civil engineering designing and construction aspects. A capability to estimate future siltation rates in small dams is essential to ensure that:  dams are not constructed in catchments with excessively high sediment yields; dams are sized correctly; catchments where the rapid introduction of soil and water conservation or other measures will be essential if a reasonable dam life is being obtained, are identified early enough for remedial activities to have a significant impact on dam siltation.

    Methodology
    Sediment yield from a small dam catchment is determined by rates of soil erosion, and the sediment transport ation and deposition processes that control the delivery of eroded sediment via the fluvial system to the catchment outlet. The characteristics of the catchment, including soil types, land use, rainfall distribution and intensity, and conservation activities all affect sediment yields, which in semi-arid regions vary widely from year to year. Koohbord dam watershed with a total area of 38.29 square kilometers in Kohgiluyeh and Boyerahmad province is one of the watersheds without a sedimentation data, which requires the use of empirical models for estimating sediments, so that the obtained data is the basis for the management plans of dam watershed. The used procedure based on an empirical sediment yield predictor that combines quantitative information on the catchment area, annual rainfall and slope, with qualitative factors describing soils, vegetative cover, and evidence of accelerated erosion. The qualitative factors scored in a rapid catchment characterization exercise. Scores for soil type and drainage, erosion status and vegetation cover used with data describing the slope of the main stem river, the catchment area, and the annual rainfall. From the information the sediment yield can predicted, using an empirical function (which is) developed from small dam catchment and sedimentation data. The catchment annual rainfall and area also will calculate. The slope of the main stem river is obtained from 1:50 000 maps. The elevation difference between the catchment boundary and the river bed at the dam location is divided by the distance, measured along the main stem river, from the catchment boundary to the dam site.

    Results
    The results showed that the amount of sediment yield in the Koohbord dam watershed is 13.8 tons per hectare per year, taking into account the sediment delivery ratio of 0.18, this sediment yield rate is equivalent to 45.16 tons per hectare per year for soil erosion. It is estimated that after 20 years the lifetime of the dam, about 27% of the initial capacity of dam’s storage is lost. Meanwhile, due to the evaporation, about 32% of dam’s volume is lost too.
     Discussion & Conclusions: The catchment must be large enough to ensure that the annual runoff fills a dam.  It is suggested a lower limit for the catchment area derived by dividing the dam capacity by 10% of the annual rainfall (Dam capacity in m3, rainfall in m, gives the minimum catchment area in m2). If the runoff coefficient for the catchment were 0.1, a typical value for small, semi-arid catchments, this criterion results in a ratio of dam capacity to annual inflow volume of 1, i.e. the dam would store all of the annual runoff generated in an average year. Minimum extracted watershed area of this indicator (38/7 km2) is approximately equal to the area of the catchment area of the Koohbord dam (38/30 km2) and technically the dam has been properly located. A catchment area larger than the minimum area derived using the criteria described above will increase the probability of the dam filling from emptiness in drier than average years. However, there is also an upper limit on catchment areas, particularly in regions with significant sediment yields. Dams in catchments with a large annual runoff in comparison to their storage volume will have rapid siltation rates, and will require large and costly spillways. A lower limit on the ratio between dam capacities to the annual inflow of 0.1 recommended for small dams, in catchments where significant sediment yields anticipated dams with a capacity to inflow ratio of less than 0.3 are not recommended. In the Koohbord dam watershed, the ratio between the capacities of the dam to the annual flow is 1.2, In fact, the annual flow is 0.8 times the capacity of the dam. It seems that the dam has not been properly located. The ratio of the volume of stored water to the volume of earthwork required to justify constructing a dam (in economic terms) depends on the value of the stored water compared to the dam construction costs. It suggested that this ratio should be above eight, and if it is below five the dam site should reject. In the Koohbord dam watershed, the ratio between the volumes of stored water to the volume of earthwork required to constructing a dam is 12, which suggests that the construction of the Koohbord dam is economically feasible.
    Keywords: reservoir capacity, soil erosion, soil type, drainage, vegetation status
  • Ebrahim Asghari, Kaljahi Dr*, Sakineh Hoseinpour , Ata Ollah Nadiri Dr Pages 42-61
    Introduction
    Urmia Lake as the largest domestic lake in Iran is drying. Climate change in the northwest of Iran, rainfall reduction and evaporation, due to the increase in average temperature in the Northwest of the country accompanied with the involvement of human factors such as dam construction, have caused an irreparable environmental hazard in the northwestern of Iran. Undoubtedly, extending the frequency of events and expanding the range of salt dust originating from the bed of Urmia Lake is the most important consequence of the lake’s dryness (Zarasavandi, 2014).
    There have been various ideas about the risk of salt dust caused by the dryness of Urmia Lake. It seems that some of them do not have an exact scientific basis. In this article, the north-eastern zone of Urmia Lake is divided into different parts in terms of texture and sediments and has been investigated for the potential of salt dust generation.

    Methodology
    In this research, the determination of producing the potential of salt dust is carried out through four steps including: collecting information, field and laboratory studying, checking meteorological data, and determining the winds speed and direction in regions. Different physical and chemical tests have been carried out on samples taken. Sampling and evaluating of the texture and structural properties of surface sediments, such as determining the horizons that makes sediment in each area, thickness of salt shells, type of salt shells, presence of sand cover at sediment surface to integrate with the results of wind tunnel tests, meteorological information (climate region and wind speed and direction), grain size which determine the production of salt dust potential in the area has been studied.
    The sampling was done according to the texture changes and the types of sediments in studied areas. Wind tunnel was used to study the evaluation of erosion of the sediments of the study area. At first, the samples were dried to be placed in the most suitable condition for wind erosion. Subsequently, samples were poured into test trays and its surface was carefully flattened and then weighed.  Afterwards, it was placed inside the wind tunnel channel.

    Results
    The results of the research were obtained from satellite images, field studies, meteorological studies, sampling, and laboratory experiments and local inquiries. Satellite images of the 15 past years have been surveyed and the lake’s drying process has been investigated. Based on the survey of satellite images in the northeast of the lake between the Sharaf- Khaneh port and the Islamic island, it has dried up over 500 square kilometers and has come out of the water. In order to investigate the prevailing winds in the region, according to the weather data of Tabriz station, wind rose-diagram has been drawn. Due to the fact that low-speed winds are not capable of producing dust storms, winds were eliminated at speeds less than 8 m/s and wind rose-diagram was drawn. The direction of most winds is to eastward.
    In studied areas, samples from soil or saline sediments were removed from a few points on each substrate and transferred to the laboratory. Different physical and chemical tests have been carried out on samples taken. The most important experiments including grading tests, morphometric soil particle studies, salt content determination, XRD and wind tunnel testing. To study of the sediment potential for dust generation as well as sediment erosion threshold speed has been used of wind tunnel. The experiment began with low wind speed and gradually increased the wind speed to determine the speed of erosion threshold. At low speeds, there was no effect in wind erosion, but with increasing the speed for each sample at a rate of speed (threshold speed), erosion began.
    This experiment was performed on samples from different subzones. At low velocities, any erosion was not observed in sediments. Also were tested salt samples in wind tunnel. The samples were placed for 15 minutes in wind tunnel at different speeds up to 30 m/s. Its weight did not change before and after being placed in the tunnel, this is a sign of a lack of wind erosion impact on the salt shells. Sharaf- Khaneh and Sheikhvali area sediments have the most erosion modulus because of the coarse size of the sediment grains compared with the sediments of the Islamic island. The wind erosion modulus of the studied sediments at speeds of about 22 m/s, the equivalent of 80 km/h increased.  Discussion & Conclusions: Based on satellite images studies and field studies, and types of sediments, the North East Zone of Urmia Lake is divided into four subzones. Subzones separated outwards from the old coast of lake to center of lake that contains, loose soil subzone, soil saltyferous subzone, salt soilferous, subzone and pure salt subzones. The area of these subzones are about 160, 220, 170 and 58 square kilometers, respectively. Each of these subzones has special sedimentary texture.According to the results of wind tunnel testing, the module of sediment erosion of northern area of the Islamic island is 1157  and for Sharaf-Khaneh sediments is 1948 . The lowest threshold speed of wind erosion belongs to the saline sediments of the northern shore of the Islamic island. The size of sediments in this area is smaller than other areas and the amount of salinity of sediments in this area is more than other areas too. The amount of erosion for the coastal deposits of Sheikhvali and Sharaf-Khaneh areas has been high, which is due to the coarser size of these sediments grains than the northern shore of the Islamic island. The size of sediments grains in these areas was more sand and at a very low rate silt and clay and therefore, they had low dusting potential.  According to the results of sediment grading tests, wind tunnel and field investigations, it was found that the area near the Islamic island has a higher dust potential than the northern parts of the Sharaf-Khaneh shore and the Sheikhvali shore. Wind tunnel tests showed that the soil moisture plays a major role in preventing wind erosion. Fortunately, the results of this research show that the salt storms did not have considerable impact on agriculture and gardening of area so far.
    Keywords: Salt dust storm, Urmia Lake, Wind tunnel, Wind erosion
  • Aghil Madadi , Imanali Belvasi I* Pages 62-83
    Introduction
         Soil erosion is a process in which soil is separated from its original bed and transported to another location with the help of a moving agent [17]. Soil erosion is one of the serious problems in the watersheds of Iran and can be considered as one of the most important barriers to sustainable agriculture and natural resources development [6]. Soil erosion results in the destruction of agricultural land, the reduction of soil fertility, environmental negative impacts, and a very important threat to the sustainable production of agricultural products [8]. Erosion, the result or results of the interaction of a set of natural and human factors, which, in accordance with the specific circumstances of the region, are one or more factors acting as the main and determining factors [7]. In general, erosion is a natural phenomenon that human activities can exacerbate. Historical evidence suggests that erosion and destruction of soil have resulted in the collapse and destruction of human civilizations [9] .Awareness of the extent of erosion in catchment areas, the possibility of comparing them and identifying critical basins and implementing watersheds. The amount of erosion and destruction of the land requires the zoning of erosion of the land for the preparation and collection of information [8]. Destruction of vegetation (especially the plant species of moss, which is the dominant species of the region) and the cutting of trees and shrubs (oak and orange trees, which form the largest area of the forests of the area) cause soil to be deflated against erosion and cause debris to be gutted and even swept away.

    Methodology
         In this research geological maps, topographic maps, Landsat 8 satellite images, climatic data of the study area in research, including temperature and precipitation, and the 30-meter-high elevation digital model of the study area were used to prepare the slope map, the slope direction and the extraction of the waterways. ArcGIS software was used to create databases, spatial and spatial analysis, and finally to implement the model and use the ENVI software to process satellite imagery. Fuzzy logic is a logic of several values, that is, its parameters and variables, in addition to the number of 0 or 1, can take all the values between these two numbers. The basis of the differences between fuzzy methods and other methods is to define the membership function. The membership function can be used to determine the degree of attribution of the elements of the reference set to its subset. The operator of the fuzzy society is the collection community. In this way, it extracts the maximum membership. The fuzzy subscription operator is the collection subscription. In that way, it extracts the minimum degree of membership. Fuzzy algebraic multiplication multiplies all the information layers together. Because of the nature of the numbers between zero and one, which is the same as the membership in a fuzzy set, the operator makes the number of the numbers smaller and goes down to zero. The complementary fuzzy algebra operator is obtained by the algebraic multiplication. Therefore, in the outbound map, unlike the fuzzy algebraic operator, the value of pixels goes toward one. The fuzzy gamma operator is the product of multiplication, fuzzy coherent multiplication in the fuzzy algebraic summation. The results obtained from this operator are more accurate than other operators. To evaluate the accuracy of the model, Kappa statistical coefficient was used.

    Results
         The results show that the kappa statistical coefficient shows that the 0.97 fuzzy gamma operator with 0.83 kappa coefficient has excellent accuracy in soil erosion zonation in Seymareh Chinar basin. Investigating the results of this study shows that areas with a steep slope, poor vegetation, bay lands, presence of limestone and dolomitic stones have much more erosion. This type of erosion is located in the northwest, south and southwest of the studied basin. In the south and southwest of the region, due to the high slope, low soil depth, excessive grazing of livestock, degradation of vegetation and forest by the inhabitants of the region and plowing the land towards the slope, led to greater erosion. In the west, south and center of the area due to uneven topography and in some areas, soil depth, cereal, steppe, in some cases, blueberries and slopes less than other parts of the area, erosion is less. According to the results of this research, as well as field observations and lack of attention of the people of the area to soil degradation and destruction of the dominant vegetation of the region, it seems that the study area in research needs urgent planning to prevent soil erosion. This suggests that in this basin, the separation and displacement of soil particles is so limited that implementation of the necessary water and land conservation programs and the use of land has a lot of limitations.  Discussion & Conclusions:      To do this study, using a fuzzy logic model, the database consists of slope, directional, petrographic, land use, lagoon, rainfall, soil and channel formation, and then the required data were obtained by processing the data. The operators of the fuzzy logic model were used. The result of the fuzzy community operator generated the maximum membership. The fuzzy share operator extracted the minimum membership. The result of the operator of the fuzzy algebraic multiplication is reduced to zero numbers. The output map of the operator of the fuzzy algebra sum of the value of the pixels is close to the maximum. In order to modulate the very high sensitivity of the fuzzy algebraic operator and the very low accuracy of the fuzzy algebraic operator, a 0.9% gamma-gamma operator was used. Based on the zoning done using fuzzy function, 16.19, 31.37, 27.77, 17.98, and 34.66 percent of the area of the area are located in very low, moderate, high and very erosion classes. Kappa coefficient was 0.83 for fuzzy logic model. Eliminating the dominant vegetation of the region, especially the mossy vegetation, which has roots and prevents soil erosion, cuts off oak trees to plow in the direction of slope and changes the unauthorized use, all have added to the severity of erosion in this area.
    Keywords: Geographic Information System, Seymareh Chinar Basin, Erosion, Fuzzy Logic Model
  • Shirin Mohammadkhan*, Anvar Moradi , Fatemeh Moradipour Pages 84-103
     
    Introduction
    Fluvial and aeolian processes are important factors in changing the surface of morphology in the Earth. When rivers and sand dunes meet, the transportation of sediment  between them can lead to one of the systems or both  of them change. With their connection between river sediment and wind systems there would be lots of reactions, but very little has been studied. According to the previous studies in Iran, river and wind systems have been studied separately. Whereas ground-level processes rarely interact with each other, there is so many important proofs that river and wind processes simultaneously are interacting. The interaction between these two processes is important for mantaining the purposes of an intergrated management of fluvial and aeolian systems, considering the wide vastness of Iran’s effect by wind and river erosion. This research is the first inventory of interactions between rivers and sand dunes with the aim of systematically analyzing of the interactions between fluvial and aeolian geomorphology and determining the dominance of Fluvial and aeolian systems in different environments.

    Methodology
    The method of this research is descriptive-analytical. This study is a visual search of  the interactions between rivers and sand dunes using satellite imagery hosted by Google Earth (GE) as well as Landsat 8 (USGS) images in the arid and semi-arid regions of Iran. Using these images, surface and landforms from fluvial and aeolian processes can be identified. Because of this reason, this study focuses on the interactions between sand dunes and rivers, where the characteristics of both are easily reconized. To intensify this research, library resources including books and articles have also been used. The search of methodology started at the margins of dryland areas visually identified within Google Earth. Than Identifiable river courses were (bieng  traced up and down the streams to find places where aeolian dunes interact with river courses. Interactions were identified at a regional scale. In this research, 304 sites, where rivers and sand dunes met, are identified and analyzed  by using imagery satellites for the first time in the country. The classification scheme of Liu and Coulthard (2015) has been used to classify the types of interactions between the sand dunes and rivers. At each site a key word   has been used to classify the types of interactions between the sand dunes and rivers. At each site key attributes such as river direction, sand transport direction, fluvial aeolian meeting angle, sand dune type, and river channel pattern were identified and their relationships between each factor was investigated. Based on the data, six different types of interactions between rivers and sand dunes were classified, that reflected changes between the fluvial and aeolian systems.

    Results
    According to the data from 304 sites in arid and semi-arid regions of the country, although longitudinal sand dunes are most occurring among all the sand dunes, a similar distribution of channel patterns can be observed for each level . Braided channel patterns have the highest frequency and straight channel patterns and others have the lowest frequency. In all of different channel patterns, the most frequent interaction is fully fluvial dominant and the  lessfrequent  one which is the type of mostly aeolian dominant and balanced. In braided channel patterns, the frequency of interactions from types of mostly aeolian dominant and balanced more than other patterns. In balanced conditions, rivers and dunes connect more in the angles of 45 to 90 degrees  Discussion & Conclusions Four variables changes has been analyzed to seek possible relationships between fluvial and aeolian systems, including dune type, channel pattern, meeting angle and the interaction. The results showed that there is a significant relationship between the type of meeting angle and the type of sand dune, the meeting angle and the type of interaction, the channel pattern and type of interaction. These relationships have shown that active river channel patterns are most common where aeolian or fluvial systems are dominated, but the balance between them is not sustainable. There was also no relationship between sand dunes and channel patterns. The results of this study are in line with Liu and Coulthard (2015) studies that show significant relationships between fluvial and aeolian processes. The results of a survey of 304 distributed sites in the arid and semi-arid regions of Iran showed an extensive interaction between rivers and sand dunes. According to the results, it can be said that in many sites, wind and river processes have a significant impact on each other and then on the landforms and geomorphology of the site. Nevertheless, more research is required to investigate how each fluvial and aeolian processes affect each other, as well as geomorphologic changes caused by them in Iran.
    Keywords: Fluvial–aeolian interaction, Dunes, River, wind, river direction, Geomorphology
  • Mohammad Ali Fakhari , Majid Lotfalian , Seyed Ata ollah Hosseini*, Abdolvahed Khaledi Darvishan Pages 104-118
     
    Introduction
    Erosion is a geomorphologic and natural process that is always seen across the world, but this process is triggered by human activities, such as road construction, resulting in a significant negative impact on water resources, soil, environment and national economy. According to the above, preventing soil erosion is an important target in the management and conservation of natural resources. Basic measures to reduce road environmental damage begin at the design stage. There are, however, erosion-sensitive areas in the embankment slopes that are created in various dimensions and in different ways during use of the road. Areas with mild slopes and low area, over the time, are naturally stabilized and restored, but larger or sloping mountainous areas, are stabilized and rebuilt or, despite the passage of time, not only stable, but also increasing the extent of destruction levels. Geotextiles are additives and permeability that are used in conjunction with soil, rock, or any materials associated with geotechnical engineering as a supplement, which modifies and sustains the soil structure. Geotextiles are divided into two groups of the original structure and the original disorganized structure in a general classification. They are made of synthetic fibers (polypropylene, polyethylene, and polyamide) or natural fibers (hemp, coconut fiber, chips, rice straw and grains, palm leaves) in different designs in terms of size and shape and according to their functions and needs. In this study, the effectiveness of protective treatment, including two types of uncontrolled natural straw geotextile and rice straw and wood chips on the establishment and emergence of two species of woody and native forests including alder forests and forest canola (jaw), as well as soil erosion In the ridge of the forest road was carried out.
    2-
    Methodology
    After preparing the ground, two experimental treatments including straw and chips of rice, wood chips (due to abundance, low cost and easy accessibility), along with the planting of one-year-old seedlings of two species of forest species of  Ader and forest witch (due to natural presence in Similar areas of erosion, indigenousness, easy establishment, rapid growth, abundant  rootstock, and low airy zipper (Tuttle et al., 1992) in three completely randomized blocks, and similarly, at a surface of about 72 square meters (12 × 6 m 2) ) used. Each block was divided from the margin of the road down the slope and in the direction of the slope into three rows (repeating) and each row in the direction of the alignment lines to three plots of 8 square meters (4 × 2 m 2). Therefore, each block was consisted of 9 sub plots of 8 square meters that were planted in each row (replicate) in a subset of Alder and the next plot of willow forest with density of one seedling per square meter. The remaining Crete had no seedlings in each row. The method of planting and planting seedlings in plots was based on species type and random systematic. Therefore, in each block, three plots were used for the alder species, three plots for forest beet and three plots without seedlings and no cover (control) and the plot was split plot. All of the plots in each block were enclosed around the plots in order to prevent the penetration of water and the spillage of rain fed particles into adjacent plots. Runoff and precipitations from the rain after passing through the outlet were transferred to a runoff tube (120 liters). All blocks and plots were completely identical and the blocks were separated by type of treatment and plots according to the type of planted species.3-
    Results
    The results of field studies showed that the control treatment had the highest runoff and sediment mass in comparison with the protective treatments, followed by straw and chalk and the lowest amount of runoff and sediment volume was related to woodchip treatment. In general, the difference between protective and control treatments was significant. In other words, protective treatments had significant effects on decreasing runoff and sediment mass (soil loss) (P ≤ 0.05). There is no significant difference between protective treatments, but the particle has the highest effect. The average of total runoff for control, straw, and shredded and woodchip plots was 6.99, 6.36 and 3.21, respectively. The mean amount of sediment mass for the control plots, straw and chips and wood chips. The ordering was equal to 5.35, 2.71, and 1.71 g. Straw, chop and chipped wood reduced the concentration of sediment (inflorescence) (P ≤ 0.01). In the meantime, the straw had the greatest impact. The mean concentration of sediment for control plots, chips and straw and chaff were 1.55, 1.37 and 1.18 g / liter, respectively. The results of soil moisture content in experimental plots during the measured period and in relation to rainfall intensity showed that soil moisture changes were similar for all treatments, but the observed difference was observed in their absolute value. Soil moisture content at 2 cm depth of soil in straw, wood chips and control plots was 11.49%, 10.68% and 9.4%, respectively. In other words, protective treatments have a significant effect on soil moisture increase. The depth was 2 cm (0.01 P ≤). The results showed that the effect of experimental treatments on grass cover of plots was significant (P ≤ 0.01) and reduced the percentage of grass covering. The average percentage of grass covering for trees, chips and straw was 48%, 37% and 36%, respectively.
    4- Discussion &
    Conclusions
    The reason behind the reduction of soil loss in protective plots compared to the controlling can be attributed to the fact that the use of straw and chips of rice and shrubs that cover the surface of the plots prevents the direct collisions of rain drops with the soil area of ​​the plots and the amount of roughness Thus increasing the surface, thereby reducing the energy and rainfall erosion power. Compared to protective treatments, wood chips due to wooden texture and hard fibers which blocked the flow of water and caused more water penetration in the soil and had the greatest effect on reducing the volume of runoff and sediment yield. Similar to the results in western India, hard and rough coconut fibers were able to reduce the erosion rate by 99.63% over the projected period (before the season or season of Monsoon) and 95% after the Monsoon period of 57%. The reason for this reduction is due to the presence of a protective layer that absorbs the effect of the energy of the movement generated by the rain drops and thus prevents erosion. In the semi-arid region of the north, the coffin mat and the polyester mattress reduced the average sediment content by 99/4 and 98 / 4% and the polyester network by 5 / 5 %, respectively. Although straw, chips and wood chips compared to control (bare soil), because of their ability to maintain water, soil moisture and reduce soil loss, the growth of the diameter of the collar was 39/84% and 31/92 %. The height of the seedlings increased by 4/51% and 2/92, but their effect was not significant. Increasing water and food storage capacity in the soil can improve the growth and growth of the seedlings, as well as the proper development of its root surface. As a result, in dry months of the year (two months a year) the plants keep the drought stress. This is particularly important in the reconstruction of the slope. Straw and Chicha had the highest effect among treatments due to their ability to maintain water and maintain soil moisture. The mean of collar diameter and height increment of Alnus glutinosa was significantly higher than Salix alba. In general, results of this study showed that the use of natural geotextiles had significant effects (P ≤ 0.05) on reducing runoff and sediment. Therefore, on erosion areas and steep slopes, using these bio-engineering methods could help seedling establishment and soil erosion reduction.
    Keywords: Soil Conservation, Sediment, Runoff, Bioengineering, Natural Geotextiles