اثر رگبارهای متوالی بر مولفه‌های فرسایش پاشمانی طی دو شدت مختلف بارندگی در شرایط آزمایشگاهی

نوع مقاله : پژوهشی

نویسندگان

1 دانش ‏آموختۀ دکتری گروه مهندسی آبخیزداری، دانشکدۀ منابع ‏طبیعی، دانشگاه تربیت مدرّس و عضو انجمن آبخیزداری ایران

2 استاد گروه مهندسی آبخیزداری، دانشکدۀ منابع ‏طبیعی، دانشگاه تربیت مدرس

چکیده

واضح است که هیچ فرسایشی اتفاق نمی‏افتد مگر اینکه ابتدا جدایش توسط قطرات باران یا رواناب رخ دهد. فرسایش ناشی از اثر قطرات باران (RIIE) در نتیجۀ انرژی قطرات باران اتفاق می‏افتد. بدین‌منظور مجموعه‏ای از آزمایش‏ها برای بررسی اثر رگبارهای متوالی بر مؤلفه‏های RIIE (مانند پاشمان بالادست، پاشمان پایین‏دست، پاشمان خالص، پاشمان کل و نسبت پاشمان بالادست/پایین‏دست) برنامه‏ریزی شد. آزمایش‏ها تحت شدت‏های بارندگی 30 و 90 میلی‏متر در ساعت و در شیب پلات 5 درصد روی یک نمونه خاک جمع‏آوری‌شده از مراتع حوضۀ آبخیز کجور در شمال ایران در شرایط شبیه‏ساز باران و فرسایش خاک انجام پذیرفت. طبق نتایج مقایسۀ مؤلفه‏های پاشمان بالادست با پایین‏دست در شدت بارندگی 30 و همچنین در شدت بارندگی 90 میلی‏متر در ساعت در توالی‏های مختلف دلالت بر نبود اختلاف معنا‏دار در آنها (05/0 > P) با استفاده از آزمون تحلیل واریانس یک‏طرفه در نرم‌افزار آماری SPSS نسخۀ 22 داشته است. همچنین تحلیل نتایج مقایسه‏ای مؤلفه‏های RIIE شامل پاشمان بالادست، پاشمان پایین‏دست و پاشمان کل در توالی سوم، چهارم و پنجم در دو شدت بارندگی 30 و 90 میلی‏متر در ساعت در سطح 95 درصد معنا‏دار بود. در حالی ‏که پاشمان خالص و نسبت بالادست/ پایین‏دست تحت شدت‏های بارندگی 30 و 90 میلی‏متر در ساعت در توالی‏های مختلف رگبار غیر‌معنا‏دار (05/0 ≥ P) بوده است. همچنین نتایج بیان‌کنندۀ افزایش 5/2 برابری ضریب تغییرات پاشمان خالص و کل در شدت بارندگی 30 میلی‏متر در ساعت نسبت به 90 میلی‏متر در ساعت بود.
 
 
 

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effects of consecutive storms on splash erosion components for two different rainfall intensities under laboratory conditions

نویسندگان [English]

  • Mahboobeh Kiani-Harchegani 1
  • Seyyed Hamidreza Sadeghi 2
1 PhD Graduate, Department of Watershed Management Engineering, Faculty of Natural Resources, Tarbiat Modares University and Member of Watershed Management Society of Iran
2 Professor, Department of Watershed Management Engineering, Faculty of Natural Resources, Tarbiat Modares University
چکیده [English]

Obviously, no erosion occurs unless detachment takes place first, either by raindrop or runoff. The Raindrop-Impact-Induced Erosion (RIIE) occurs when detachment is caused by raindrop energy. For this purpose, a set of laboratorial experiments were scheduled to examine the effects of consecutive storms on RIIE components (i.e. upward splash, downward splash, net splash, total splash and upward splash/downward splash). The experiments were conducted for two different rainfall intensities of 30 and 90 mm h−1 at slope of 5% under rainfall simulation and soil erosion for a soil collected from Kojour rangeland watershed in the Alborz Mountains, northern of Iran. The comparative analysis of the results showed that there was no significant difference between upward with downward splash under rainfall intensity of 30 as well as under rainfall intensity of 90 mm h−1 in consecutive storms (p ≤ 0.05) using One-Way ANOVA in SPSS Statistics 22 software. In addition, the obtained results indicated that RIIE components viz. total and upward and downward splash were significantly different (p ≤ 0.01) under rainfall intensities of 30 and 90 mm h−1 in the third, fourth and fifth consecutive storms. However, net splash and upward/downward splash proportion was not significantly different (p > 0.05) under rainfall intensities of 30 and 90 mm h−1 in different consecutive storms. The results also indicated a 2.5-fold increase in coefficient of variation of net splash and total splash under rainfall intensity of 30 mm h-1 then the rainfall intensity of 90 mm h-1.

کلیدواژه‌ها [English]

  • Event Storm
  • Rainfall simulation
  • splash cup
  • net splash
 
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