تأثیر شیب بستر جاده‌‌های جنگلی بر مقدار رواناب و رسوب تولیدی (مطالعة موردی: جنگل کوهمیان‌ـ‌آزادشهر)

نوع مقاله: مقاله پژوهشی

نویسندگان

1 کارشناس ارشد مهندسی جنگل، دانشکدۀ منابع طبیعی دانشگاه تهران، کرج، ایران

2 استادیار گروه جنگل‌داری و اقتصاد جنگل، دانشکدۀ منابع طبیعی دانشگاه تهران، کرج، ایران

3 استاد گروه احیای مناطق خشک و کوهستانی، دانشکدۀ منابع ‏طبیعی دانشگاه تهران، کرج، ایران

4 استادیار گروه مرتع و آبخیزداری، دانشگاه گنبدکاووس، گنبد، ایران

5 استاد گروه جنگل‌داری و اقتصاد جنگل، دانشکدۀ منابع طبیعی دانشگاه تهران، کرج، ایران

چکیده

جاده‌‌های جنگلی دسترسی به منابع جنگلی را آسان می‌کنند و بدون وجود آن‌ها نمی‌‌توان به‌خوبی عملیات بهره‌‌برداری، حمل‌و‌نقل، حفاظت، و اکوتوریسم را مدیریت کرد. جاده‌‌های جنگلی از مهم‌ترین منابع اصلی تولید رسوب در این مناطق به‏شمار می‌‌روند. امروزه، فرسایش خاک و پیامدهای ناشی از آن از مهم‌ترین چالش‌‌های مدیریت این جاده‌هاست و به‌‌طور جدی منابع آب و خاک را تهدید می‌‌کند. بنابراین، ساخت نامناسب جاده باعث آلودگی رودخانه‌‌های جنگلی و تهدید حیات آبزیان می‌‌شود. از مهم‌ترین استانداردهای ساخت جاده شیب طولی جادۀ جنگلی است. تعیین ارتباط شیب جاده و مقدار رسوب تولیدی کمک مؤثری به مدیریت شبکۀ جاده برای احداث جاده‌‌های جدید جنگلی مطابق با شیب مناسب می‌‌کند. این تحقیق به‌‌منظور بررسی تأثیر شیب بستر جاده بر مقدار رواناب و رسوب تولیدی با استفاده از باران‌‌ساز در سطح پلات یک متر مربعی در قالب طرح کامل تصادفی در 3 طبقۀ شیب 3ـ6 درصد، 6ـ9 درصد، و 9ـ12 درصد و 3 تکرار انجام گرفت. سپس در هریک از طبقات شیب مقدار رواناب و رسوب طی انجام شبیه‌‌‌سازی باران با شدت ثابت 81 میلی‏متر بر ساعت به‏مدت 30 دقیقه اندازه‌گیری شد. این سه بخش طوری انتخاب شد که پارامترهای دیگر از قبیل سطح رویۀ جاده، مقدار رفت‌و‌آمد، و بارندگی ثابت باشد و فقط به تأثیر شیب بر مقدار رواناب و رسوب تولیدی پرداخته شود. نتایج نشان داد متوسط رواناب ایجاد‌شده در بخش 1 (شیب 3ـ6 درصد)، بخش 2 (شیب 6ـ9 درصد)، و بخش 3 (شیب 9ـ12 درصد) به‌ترتیب 0/21، 60/35، و 10/51 لیتر به‌ازای هر متر مربع و غلظت رسوب تولیدی 54/3، 11/8، و 11/12 گرم بر لیتر برآورد شد. نتایج آنالیز واریانس نشان داد که تفاوت معنی‌‌داری در بین مقدار رواناب و رسوب طبقات شیب مختلف جاده وجود دارد و نتایج آزمون توکی نیز نشان داد که با افزایش شیب، مقدار رواناب و رسوب به‌‌طور معنی‌‌داری افزایش می‌‌یابد. نتایج این بررسی تأییدکنندة این است که رعایت شیب مجاز جاده‌‌های جنگلی عامل مهمی‌‌ در کاهش تأثیر منفی این زیرساخت‌‌هاست.
 

کلیدواژه‌ها


عنوان مقاله [English]

Effect of Forest Road Gradient on Amount of Runoff and Sediment(Case Study: Kohmiyan- Azadshahr Forest)

نویسندگان [English]

  • Mostafa Moghadamirad 1
  • Ehsan Abdi 2
  • Mohsen Mohseni Saravi 3
  • Hamed Rouhani 4
  • Baris Majnounian 5
1 M.Sc. in Forest Engineering, University of Tehran, Karaj, I.R. Iran
2 Assistant Professor, University of Tehran, Karaj, I.R. Iran
3 Professor, University of Tehran, Karaj, I.R. Iran
4 Assistant Professor, University of Gonbad e Kavoos, Gonbad, I.R. Iran
5 Professor, University of Tehran, Karaj, I.R. Iran
چکیده [English]

Roads provide access to forest resources for properly management of timber production,
transportation, forest protection and ecotourism. Forest road networks are usually the main source of
sediment in forest watersheds. Globally, soil erosion is one of the most important environmental
problems which is threaten soil and water resources. Therefore, poor planning and construction causes
pollution of forest streams and damage to aquatic life. Road Gradient is one of the main factors of road
construction standards. Determining the relation between road gradient and amount of sediment
production can be used efficiency by forest manager to choose proper gradient for new roads. This
study was conducted in Kohmiyan Forest-Gorgan, and three different segments with 3%-6%, 6%-9%
and 9%-12% gradient were selected on road network. investigation Using rainfall simulation the effect
of road gradient on amount runoff production and sediment was assessed. In three segments, other
parameter such as: roadbed, amount traffic and precipitation are similar. The results indicated that the
average amount of runoff produced in segment 1 (gradient 3%- 6%), segment 2 (6%- 9%) and
segment 3 (9%-12%) were 21.00, 35.60 and 51.10 litter respectively for each one square meter and
average amount of sediment were 3.54, 8.11 and 12.11 g/l. The results of analysis of variance showed
significant differences between amount of runoff and sediment due to road gradient. The results of
Tukey test showed significant differences among mean runoff and sediment of three segments and
increasing with increased road gradient. So keeping the road gradient in standard range is an important
factor for controlling runoff and sediment.

کلیدواژه‌ها [English]

  • Forest roads
  • Kohmiyan forest
  • Rainfall simulator
  • Road gradient
  • Runoff
  • Sediment
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