نوع مقاله : مقاله پژوهشی

نویسندگان

• روح اله رضایی ارشد ¹
• مجید محمودآبادی ²
• محمد هادی فرپور ³
• مجید فکری ³

¹ دانشجوی دکتری، گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه شهید باهنر کرمان، کرمان، ایران

² دانشیار گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه شهید باهنر کرمان، کرمان، ایران

³ استاد گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه شهید باهنر کرمان، کرمان، ایران

چکیده

رگبارهای شدید و فرساینده، به‌طور معمول با وزش بادهای تند همراه است. هرچند شناخت اثرات متقابل باران و باد اهمیت ویژه­ای در پژوهش‌های فرسایش خاک دارد، ولی تاکنون مطالعه جامعی در این زمینه و در شرایط کنترل شده آزمایشگاهی انجام نشده است. پژوهش حاضر با هدف بررسی فرسایش بین­شیاری ناشی از باران در حضور سرعت­های مختلف باد بر روی چند خاک زراعی با استفاده از شبیه­ساز همزمان باد، باران و رواناب انجام شد. چهار سرعت باد شامل صفر، 6، 9 و 12 متر در ثانیه در ارتفاع 40 سانتی­متر و سه شدت باران 30، 50 و 75 میلی­متر در ساعت بر روی سه خاک زراعی، با بزرگترین اندازه ذرات 2، 75/4 و 8 میلی­متر ایجاد و شدت فرسایش بین­شیاری اندازه­گیری شد. نتایج نشان داد که سرعت باد تأثیر معنی­داری بر شدت فرسایش بین­شیاری دارد. با افزایش سرعت باد از 6 متر در ثانیه به 9 و 12متر در ثانیه، شدت فرسایش بین‌شیاری به‌طور معنی‌داری افزایش یافت که این موضوع نشان از وجود یک آستانه برای سرعت باد در تشدید فرسایش بین‌شیاری دارد. میانگین شدت فرسایش در سرعت صفر، 6، 9 و 12 متر در ثانیه باد به ترتیب ^4-10 ×43/0، ^4-10 ×54/0‌، ^4-10 ×97/0‌ و ^4-10 ×46/1‌ کیلوگرم بر متر مربع در ثانیه اندازه­گیری گردید. هم‌چنین با افزایش شدت باران و کاهش اندازه خاکدانه‌ها، شدت فرسایش بین­شیاری افزایش نشان داد. یافته­های این پژوهش، اهمیت سرعت باد به ویژه سرعت­های بیش‌تر از مقدار آستانه را در بررسی فرسایش بین‌شیاری نشان می­دهد.

کلیدواژه‌ها

• باران متأثر از باد
• فرسایش بین شیاری
• تونل باد
• شبیه سازی فرسایش

موضوعات

• فیزیک، فرسایش و حفاظت خاک

عنوان مقاله [English]

Wind-driven rain influence on interrill erosion using the simultaneous wind-rainfall-runoff simulator

نویسندگان [English]

• Ruhollah Rezaei Arshad ¹
• M Mahmudabadi ²
• Mohammad Hady Farpoor ³
• Majid Fekri ³

¹ Department of Soil Science, Agriculture Faculty, Shahid Bahonar University of Kerman, Iran.

²

³ Dep. soil science

چکیده [English]

Introduction Under natural conditions, intensive and erosive storms commonly associate with high-speed winds. In fact, wind velocity affects water erosion rate through enforcing falling drops and enhancing rainfall erosivity. Therefore, knowledge of interaction between wind and rain as erosive agents on interrill erosion is of prime importance. However, no comprehensive study has been done on this topic under controlled laboratory conditions. This study was conducted to investigate interrill erosion affected by different rain intensities and wind velocities on several soils with different aggregate size distributions using the Simultaneous Wind-Rainfall-Runoff Simulator (SWRRS). For this purpose, a multisystem was constructed for the first time in Iran to investigate the simultaneous effects of wind and rain erosivity agents on soil erosion under laboratory conditions.
Materials and Methods The simulator was calibrated in two cases. First, the intensity and uniformity of the simulated rains were assessed for each nozzle, separately. Second, the calibration procedure was performed for different combinations of the selected nozzles to achieve the best performance. For each case, different water pressures were generated to introduce several water discharges and make initial raindrop velocities. Afterwards, the interrill erosion experiment was done using four constant wind speeds including 0, 6, 9 and 12 m s^-1at the height of 40 cm which were applied in combination with three rain intensities of 30, 50 and 75 mm h^-1 on three soil samples with different aggregate size distributions (D_2mm, D_4.75mm and D_8mm). Each treatment was conducted at three replicates under laboratory controlled conditions. By using different wind speeds, rain intensities and soil aggregate sizes, interrill erosion rate was measured under steady state conditions.
Results and Discussion Results showed that wind velocity has a significant effect on interrill erosion rate and the interaction between wind and rain on interrill erosion was significant, as well. Although, there was no significant difference between the erosion rate at wind velocity of 0 and 6 m s^-1, the wind velocity of 9 and 12 m s^-1 showed significant difference with and higher erosion rates than the velocity of 6 m s^-1. The mean erosion rate at wind velocities of 0, 6, 9, 12 m s^-1 was 0.43 × 10^-4, 0.54 × 10^-4, 0.97 × 10^-4 and 1.46 × 10^-4 kg m^-2 s^-1, respectively. With increasing rain intensity from 30 to 75 mm h^-1, the erosion rate increased from 0.52 × 10^-4 to 1.16 × 10^-4 kg m^-2 s^-1. On average, the erosion rate of the soil containing larges aggregates i.e. D_8mm (0.73 × 10^-4 kg m^-2 s^-1) was less than that with the finest aggregates i.e. D_2mm (0.99 × 10^-4 kg m^-2 s^-1). The findings of this study highlighted the importance and necessity of more attention to wind speed particularly those velocities faster than a threshold velocity in the study of interrill erosion.
Conclusion In arid and semi-arid regions such as most parts of Iran, rainstorms are usually accompanied by strong winds. Despite the undeniable influence of wind on the erosive power of rain, a host of research has investigated water and wind erosion processes, separately. Therefore, this study was done to investigate the simultaneous effect of wind velocity and rain intensity on interrill erosion rate in three soil samples. The results indicated that wind velocity has a remarkable influence on interrill erosion rate due to wind-driven rain. Wind velocities faster than 6 m s^-1 increased interrill soil erosion rate, particularly those combined with higher rain intensities. This is due to an increase in the velocity of falling raindrops on the soil surface which results in greater kinetic energy. Also, the findings showed that the soil containing coarser aggregates due to greater random roughness exhibited less sensitivity and interrill erosion rates as compared with the soil having finer aggregates, especially at faster wind velocities. The rate of interrill erosion in soil D_2mm was 1.35 times higher than soil D_8mm indicating the importance of random roughness. In addition, there was no significant difference between the measured erosion rates at wind speeds of 0 and 6 m s^-1, in all cases. However, with increasing wind speed from 6 to 9 and also to 12 m s^-1, significant increases in soil erosion rates were observed. Accordingly, a threshold wind velocity can be considered in wind-driven interrill erosion. The findings of the present study can be applied for better understanding and modeling of water and wind erosion mechanisms and dominant processes.

کلیدواژه‌ها [English]

• Wind-driven rain
• Interrill erosion
• Wind tunnel
• Erosion simulation