اثرات اندازه رسوب روی ظرفیت جداسازی جریان شیاری در شیب‌های تند سراوان رشت

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه علوم خاک، دانشکده کشاورزی، دانشگاه گیلان، گیلان، رشت، ایران

2 دانشیار گروه علوم خاک، دانشکده کشاورزی، دانشگاه گیلان، گیلان، رشت، ایران

3 دانشیار گروه مهندسی آب،، دانشکده کشاورزی، دانشگاه گیلان، رشت، ایران

4 دانشیار گروه علوم خاک، دانشکده کشاورزی، دانشگاه تهران،کرج، ایران

چکیده

حداکثر مقدار جدا شدن خاک به دلیل جریان سطحی رواناب، به عنوان ظرفیت جدا شدن خاک نامیده می­شود. مطالعه حاضر با هدف بررسی اثر کلاس‌های اندازه ذرات بر ظرفیت جداسازی جریان شیاری (Dc) در حوزه آبخیز سراوان (شمال ایران) انجام شد. برای این منظور، تغییرات Dc در نمونه­های خاک با سه کلاس اندازه ذرات (0-1 ، 1-2 و 2-3 میلی­متر) تحت شرایط آزمایشگاهی از طریق یک فلوم آزمایشی در پنج درجه شیب (1/4 تا 3/38 درصد) و پنج دبی جریان (26/0 تا 67/0 لیتر بر متر در ثانیه) با پنج تکرار اندازه­گیری شده است. نتایج نشان داد که ظرفیت جداسازی جریان شیاری در کلاس 3-2 میلی‌متر در مقایسه با سایر کلاس­های اندازه ذرات به طور معنی­داری بالاتر است (p < 0.05). قدرت جریان واحد به عنوان پیش­بینی کننده بسیار دقیق ظرفیت جداسازی جریان شیاری در زمین جنگلی حوزه آبخیز سراوان بود. فرسایش‌پذیری شیاری که با استفاده از رابطه Dc و تنش برشی جریان آب محاسبه شد، کم‌ترین مقدار را در کلاس ذرات 1-0 میلی‌متر داشت. به طور کلی، این مطالعه تأیید کرد که ذرات با اندازه بزرگتر از 2 میلی‌متر روی شیب‌های تند بیش‌تر در معرض فرسایش و جدا شدن از طریق رواناب سطحی در اکوسیستم‌های محیطی حساس مانند پارک جنگلی سراوان در بخش شمالی ایران هستند.

کلیدواژه‌ها


عنوان مقاله [English]

The Effects of Sediment Size on Rill Detachment Capacity in Steep Slopes of (Saravan, Rasht)

نویسندگان [English]

  • Misagh Parhizkar 1
  • Mahmoud Shabanpour 2
  • Mohamadreza khaledian 3
  • Hossein Asadi 4
1 Soil Science Department, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran
2 Soil Science Department, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran
3 Water Engineering Department, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran
4 Soil Science Department, Faculty of Agricultural Sciences, University of Tehran, Karaj, Iran
چکیده [English]

The maximum value of soil detachment due to overland flow is the soil detachment capacity. The present study aimed to evaluate the effect of particle size classes on the rill detachment capacity (Dc) in Saravan watershed (North of Iran). For this purpose, the variations of Dc have been measured on soil samples with three particle size classes (0-1, 1-2 and 2-3 mm) under laboratory conditions through a flume experiment at five slope gradients (4.1 to 38.3%) and five flow rates (0.26 to 0.67 Lm-1 s-1) with five replications. The results showed that the Dc in 2-3 mm class was significantly higher than the other particle size classes (p < 0.05). The unit stream power was found to be very accurate predictor of the Dc in forestland of Saravan watershed. Rill erodibility, which calculated by relationship of the Dc and the water flow shear stress, had the lowest value in 0-1 mm class. Overall, this study has confirmed that the particles with size larger than 2 mm on steep slopes are more susceptible to erosion and separation by surface runoff in delicate environment ecosystems, such as the Saravan Forest Park in Northern part of Iran.

کلیدواژه‌ها [English]

  • Forest ecosystem
  • shear stress
  • Soil erosion
  • Unit Stream Power
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