بررسی تغییرات زمانی فرسایش شیاری در خاک حساس به فرسایش تحت باران‌های با شدت متفاوت

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری، گروه علوم خاک، دانشکده کشاورزی، دانشگاه زنجان

2 دانشیار گروه علوم خاک ، دانشکده کشاورزی، دانشگاه زنجان

چکیده

فرسایش شیاری، یکی از عوامل اصلی هدررفت خاک در سازندهای مارنی است. این سازندها بسیار حساس به فرآیندهای فرسایش آبی بوده و گستره نسبتاً بزرگی را در برخی حوزه‌های آبخیز مناطق خشک و نیمه‌خشک دربر می‌گیرد. اطلاعات در مورد تغییرات زمانی فرسایش شیاری طی یک رخ‌داد بارندگی و تأثیر ویژگی‌های جریان بر آن می‌تواند در شناخت فرآیند فرسایش شیاری در دامنه‌ها کمک نماید. از این رو، این پژوهش با هدف بررسی تغییرات زمانی فرسایش شیاری و ویژگی‌های جریان در خاک مارنی تحت باران‌های با شدت متفاوت انجام شد. آزمایش در 10 رخ‌داد باران شبیه‌سازی شده با شدت‌های متفاوت از 10 تا 100 میلی‌متر بر ساعت به مدت ثابت یک ساعت با سه تکرار در شرایط آزمایشگاهی انجام گرفت. نمونه‌های خاک از سازندهای مارنی در غرب زنجان برداشت شد و در فلومی به طول چهار متر و عرض 94/0 متر و با شیب 10 درصد ریخته شد. فرسایش شیاری در کنار ویژگی‌های جریان (دبی و غلظت جریان) در فاصله زمانی پنج دقیقه از آغاز رواناب در هر یک از باران‌های شبیه‌سازی شده مورد بررسی قرار گرفت. نتایج نشان داد که تفاوت‌های اساسی از نظر زمان آغاز جریان، دبی جریان، غلظت جریان و فرسایش شیاری بین شدت‌های بارندگی وجود داشت (0001/0>p). جریان شیاری و فرسایش شیاری با افزایش شدت بارندگی سریع‌تر اتفاق افتاد. فرسایش شیاری با گذشت زمان به‌شدت افزایش یافت و در زمان‌های پایانی (حدود 45 دقیقه) تقریباً ثابت شد. غلظت جریان نیز الگویی مشابه با فرسایش شیاری نشان داد. با این حال، دبی جریان در زمان‌های پایانی افزایش چشم‌گیر پیدا کرد. به‌طورکلی این پژوهش نشان داد که با تغییر شدت باران، آستانه وقوع فرسایش شیاری و اوج آن طی بارندگی تغییر کرد. هم‌چنین روند تغییرات فرسایش شیاری طی بارندگی، با افزایش شدت بارندگی شدید شد.

کلیدواژه‌ها


عنوان مقاله [English]

Investigating temporal variation of rill erosion in an erosion-susceptible soil under different rainfall intensities

نویسندگان [English]

  • Majid Foroumadi 1
  • Alireza Vaezi 2
1 Ph.D. Student of Soil Science, Faculty of Agriculture, University of Zanjan
2 Associate professor of soil science, Soil Science Department, Faculty of Agriculture, University of Zanjan
چکیده [English]

Rill erosion is a major factor of soil loss in the marl formations. The marl formations are very susceptible to water erosion processes and cover a wide area in some watersheds in arid and semi-arid regions. Knowledge of temporal variation of rill erosion and its effect during a rainfall event can provide information on the mechanism of rill erosion in the hill slopes. Therefore, this study was conducted to investigate the temporal variation of flow characteristics and rill erosion in a marl soil under different simulated rainfalls. A laboratory experiment was carried out using 10 simulated rainfall intensities ranging from 10 mm h-1 to 100 mm h-1 with three replications. Soil samples were collected from the marl formations in west of Zanjan and separately purred to a flume with 4m in length and 0.94 m in width putted on 10% slope. Rill erosion and flow characteristics (discharge and concentration) were measured at 5-min from starting flow/ runoff in each rainfall intensity. Results indicated that there are substantial differences in the flow starting time, flow concentration and rill erosion among the rainfall intensities (P< 0.0001). Rill flow and erosion rapidly occurred with increasing rainfall intensity. Rill erosion increased speedily during rainfall and reached to approximately constant value in the last times (about 45 min). The flow concentration appeared also a similar trend with the rill erosion, while flow discharge showed an increasing trend in the last times. The study revealed that the threshold and pick time of rill erosion were strongly varied during rainfall. The variation trend of rill erosion during rainfall increases with increasing the rainfall intensity.

کلیدواژه‌ها [English]

  • Erodible particles
  • Flow concentration
  • Flow discharge
  • Marl soil
  • Rainfall simulation
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