توزیع اندازه ذرات منتقله در اثر فرسایش سطحی در شدت‌های مختلف باران و درجات شیب

نوع مقاله : مقالات پژوهشی

نویسندگان

دانشگاه زنجان

چکیده

رواناب سطحی یکی از عوامل مهم‌ در انتقال ذرات خاک و در نتیجه فرسایش سطحی خاک است. شدت باران و شیب سطح دو عامل مهم و تأثیرگذار در فرسایش سطحی می باشند. در این پژوهش، انتقال پذیری ذرات اولیه خاک به وسیله رواناب سطحی بر روی یک خاک میان بافت (رس لومی) در نه شدت باران ( از 10 تا 90 میلی متر بر ساعت) و پنج درجه شیب ( از صفر تا 40 درصد) به صورت فاکتوریل در قالب طرح کاملاً تصادفی انجام گرفت. فرسایش سطحی و توزیع اندازه ذرات فرسایش یافته با استفاده از فلوم هایی به ابعاد cm 32 × 50 تحت باران های شبیه سازی شده به مدت 45 دقیقه اندازه گیری شد. بر اساس نتایج، شدت باران 20 میلی متر بر ساعت به عنوان آستانه شدت باران و شیب 10 درصد، به عنوان آستانه شیب برای وقوع فرسایش سطحی خاک بود. میزان فرسایش سطحی تحت تأثیر شدت باران (001/0>P) و شیب سطح (001/0>P) قرار گرفت به طوری که با افزایش شدت بارندگی و شیب سطح، میزان فرسایش سطحی به طور چشم گیری افزایش یافت. تفاوت اساسی بین ذرات اولیه خاک از نظر ویژگی انتقال پذیری وجود داشت. انتقال پذیری ذرات توسط جریان سطحی نیز به شدت تحت تأثیر شدت باران (001/0>P) و شیب سطح (001/0>P) قرار گرفت. با افزایش شدت باران انتقال پذیری ذرات سیلت افزایش و انتقال پذیری ذرات شن کاهش یافت. میزان انتقال ذرات رس تحت تأثیر شیب سطح قرار نگرفت. با وجود آن که میزان انتقال ذرات شن (به جز شن بسیار درشت) با افزایش شیب به شدت کاهش یافت، انتقال پذیری ذرات سیلت و رس تحت تأثیر شیب سطح قرار نگرفت. ذرات سیلت بیشترین سهم مواد فرسایش یافته را شامل شدند. حساسیت ذاتی بالای ذرات سیلت و حتی رس به فرسایش سطحی عواملی بودند که موجب شدند با افزایش درجه شیب، انتقال آن ها تحت تأثیر قرار نگیرد. با توجه به سهم بسیار بالای ذرات سیلت در هدررفت خاک، این ذره به عنوان حساس ترین ذره خاک در برابر فرآیندهای فرسایش آبی شناخته شد.

کلیدواژه‌ها


عنوان مقاله [English]

Particle Size Distribution of Surface-Eroded Soil in Different Rainfall Intensities and Slope Gradients

نویسندگان [English]

  • Ali Reza Vaezi
  • Mahdi Ebadi
University of Zanjan
چکیده [English]

Introduction: Soil water erosion on the slope lands involves detachment, transport and deposition of soil materials due to erosive forces of raindrops and surface runoff. Surface runoff can produce relatively high soil loss and is often the dominant hillslope erosion process. The rate of surface runoff which controls surface erosion on the uniform areas in the hillsolpes, is dependent on rainfall intensity and slope steepness. In various studies, the relationships between rainfall characteristics and surface runoff were well known. Many studies have been performed on the relationship between runoff and rainfall characteristics and soil loss.The effects of slope steepness on the surface runoff and soil loss were also investigated by many researchers. In a few studies, the transportation of soil particles has been studied. For examples, some studies showed that the soil particles have different susceptibility to transport by surface flow . However, limited information is available on the effects of rainfall intensity and slope steepness on the transportability of soil particles by surface runoff in the semi-arid areas. Therefore, the objective of this study was to investigate the effects of rainfall intensity and slope steepness on the transport rate of soil particles by surface runoff in a medium soil texture in semi-arid region.
Materials and Methods: A clay loam soil with similar particle size distribution (33.15% sand, 33.22% silt and 33.63% clay) was provided to study the detachability of soil particles by surface runoff. Soil loss and particle size distribution of eroded material were determined in the soil under zero, 10%, 20%, 30% and 40% slope steepness using simulated rainfall with 10, 20, 30, 40, 50, 60, 70, 80 and 90 mm h-1 in intensity. Soil samples were filled to 32 cm  50 cm flumes with 7 cm depth and exposed to simulated rainfalls. Surface runoff, surface soil erosion and particle size distribution (PSD) of eroded material were determined in the slopes under simulated rainfalls. A total of 135 trials were carried out on 45 soil samples using the factorial completely randomized
design with three replications. Data of surface soil erosion and transportation of soil particles were compared using the Duncan's test among the rainfall intensities and slope steepness.
Results and Discussion: No surface runoff and surface soil erosion were observed in 10 mm h-1 rainfall intensity. Rainfall intensity of 20 mm h-1 appeared to be the threshold rainfall intensity to make surface runoff and surface soil erosion. Based on the results, surface runoff, surface erosion and kind of eroded soil particles were significantly affected by rainfall intensity (P< 0.001). Significant relationships were found between rainfall intensity and surface runoff (R2= 0.98) and surface erosion (R2= 0.99). Surface runoff increased strongly with increasing rainfall intensity. Increases in the rainfall intensity caused more runoff production as well as more detachment of soil surface particles . Surface runoff and surface erosion were affected strongly by the slope steepness. With an increase in the slope steepness, more surface runoff was produced and in consequence, surface soil erosion was considerably increased. Significant differences were found in the PSD of eroded material among the diffrent rainfall intensities (P< 0.001) and the slope steepness (P< 0.001). Silt showed to be the sensitive soil particles to surface erosion in rainfall intensities and slope steepness. Silt included about 66% and 74% of eroded soil particles in the rainfall intensities and the slope steepness, respectively. Sand fractions (very coarse sand, coarse sand, medium sand, fine sand, very fine sand) were the resistant soil particles to surface erosion in the rainfall intensities and the surface slopes. In higher rainfall intensities and slope steepness, more surface soil erosion was produced which was associated with the more transport of silt.
Conclusion: Rainfall intensity was the more important factor than the slope steepness in the soil loss and transportation rate of soil particles by surface runoff. Silt was the most susceptible soil particle to erosion by surface runoff in the rainfall intensities and the slope steepness. The transportation of very coarse sand and clay didn’t appear significant differences for both the rainfall intensities and the slope steepness. Protection of soil surface from raindrop impact is essential for prevention of runoff and soil loss in steep slopes especially for intensive rainfalls.

کلیدواژه‌ها [English]

  • Simulated Rainfall
  • runoff
  • Soil primary particles
  • Transportability
Akbari, S. and Vaezi, A.R. 2015. Investigating aggregates stability against raindrops impact in some soils of a semi-arid region, north west of Zanjan. 2015. Water and Soil Science, 25(2): 65-77. (in Persian)
2. Asadi, H., Ghadiri, H., Rose, C.W. and Rouhipour, H. 2007a. Interrill soil erosion processes and their interaction on low slopes. Earth Surface Processes and Landforms, 32(5): 711-724.
3. Asadi, H., Ghadiri, H., Rose, C. W., Yu, B. and Hussein, J. 2007b. An investigation of flow-driven soil erosion processes at low streampowers. Journal of Hydrology, 342(1): 134-142.
4. Asadi, H., Moussavi, A., Ghadiri, H. and Rose, C. W. 2011. Flow-driven soil erosion processes and the size selectivity of sediment. Journal of Hydrology, 406(1): 73-81.
5. Basic, F., Kisic, I., Nestroy, O., Mesic, M. and Butorac, A. 2002. Particle size distribution (texture( of eroded soil material. Journal of Agronomy and Crop Science, 188(5): 311-322.
6. Battany, M. and Grismer, M. 2000. Rainfall runoff and erosion in Napa Valley vineyards: effects of slope, cover and surface roughness. Hydrological Processes, 14(7): 1289-1301.
7. Biddoccu, M., Ferraris, S., Cavallo, E., Opsi, F., Previati, M. and Canone, D. 2013. Hillslope Vineyard rainfall-runoff measurements in relation to soil infiltration and water content. Procedia Environmental Sciences, 19: 351-360.
8. Blake, G. and Hartge, K. 1986. Bulk density, clod method. Methods of soil analysis: Part, 1.
9. Bouyoucos, G. J. 1962. Hydrometer method improved for making particle size analyses of soils. Agronomy Journal, 54(5):464-465.
10. Chartier, M., Rostagno, C. and Videla, L. 2013. Selective erosion of clay, organic carbon and total nitrogen in grazed semiarid rangelands of northeastern Patagonia, Argentina. Journal of Arid Environments, 88: 43-49.
11. Chamizo, S., Canton, Y., Rodriguez-Caballero, E., Domingo, F. and Escudero, A. 2012. Runoff at contrasting scales in a semiarid ecosystem: A complex balance between biological soil crust features and rainfall characteristics. Journal of Hydrology, 452:130–138.
12. Dahnke, W. and Whitney, D. 1988. Measurement of soil salinity. Recommended chemical soil test procedures for the North Central Region. North Dakota Agric. Exp. Stn. Bull. 32-34.
13. Edwards, W. M. and Larson, W. 1969. Infiltration of water into soils as influenced by surface seal development. Amer Soc Agr Eng Trans Asae.
14. Ekwue, E. and Harrilal, A. 2010. Effect of soil type, peat, slope, compaction effort and their interactions on infiltration, runoff and raindrop erosion of some Trinidadian soils. Biosystems Engineering, 105(1): 112-118.
15. Erskine, W.D., Mahmoudzadeh, A. and Myers, C. 2002. Land use effects on sediment yields and soil loss rates in small basins of Triassic sandstone near Sydney, NSW, Australia. Catena, 49(4): 271-287.
16. Foster, G. 1982. Modeling the erosion process. Hydrologic modeling of small watersheds, 297-380.
17. Goh, T., Arnaud, R.S. and Mermut, A. 1993. Aggregate stability to water. Soil Sampling and Methods of Analysis, 177-180.
18. Gonzalez-Pelayo, O., Andreu, V., Gimeno-Garcia, E., Campo, J. and Rubio, J.L. 2010. Rainfall influence on plot-scale runoff and soil loss from repeated burning in a Mediterranean-shrub ecosystem, Valencia, Spain. Geomorphology, 118(3): 444-452.
19. Gupta, O.P. 2002. Water in relation to soils and plants. Agrobios, India. Pp: 31-34.
20. Hasanzadeh, H., Vaezi, A.R. and Mohammadi, M.H. 2013. Runoff variations of different soils in plot scale under the same simulated rainfalls. Iranian J. of Soil and Water Research, 44(3): 245-254. (in Persian)
21. Huang, J., Wu, P. and Zhao, X. 2013. Effects of rainfall intensity, underlying surface and slope gradient on soil infiltration under simulated rainfall experiments. Catena, 104: 93-102.
22. Issa, O.M., Bissonnais, Y.L., Planchon, O., Favis‐Mortlock, D., Silvera, N. and Wainwright, J. 2006. Soil detachment and transport on field‐and laboratory‐scale interrill areas: erosion processes and the size‐selectivity of eroded sediment. Earth Surface Processes and Landforms, 31(8): 929-939.
23. Jin, K., Cornelis, W.M., Gabriels, D., Schiettecatte, W., De Neve, S., Lu, J. and Jin, J. 2008. Soil management effects on runoff and soil loss from field rainfall simulation. Catena, 75(2): 191-199.
24. Kemper, W. and Rosenau, R. 1986. Aggregate stability and size distribution.
25. Kim, J.K., Onda, Y., Kim, M.S. and Yang, D.Y. 2014. Plot-scale study of surface runoff on well-covered forest floors under different canopy species. Quaternary International, 344:75-85.
26. Kinnell, P. 2000. The effect of slope length on sediment concentrations associated with side-slope erosion. Soil Science Society of America Journal, 64(3): 1004-1008.
27. Leguedois, S. and Bissonnais, Y. L. 2004. Size fractions resulting from an aggregate stability test, interrill detachment and transport. Earth Surface Processes and Landforms, 29: 1117-1129.
28. Merten, G.H., Araújo, A.G., Biscaia, R.C.M., Barbosa, G.M.C. and Conte, O. 2015. No-till surface runoff and soil losses in southern Brazil. Soil and Tillage Research, 152: 85-93.
29. Peng, T. and Wang, S.J. 2012. Effects of land use, land cover and rainfall regimes on the surface runoff and soil loss on karst slopes in southwest China. Catena 90: 53–62.
30. Perez-Latorre, F. J., de Castro, L. and Delgado, A. 2010. A comparison of two variable intensity rainfall simulators for runoff studies. Soil and Tillage Research, 107(1): 11-16.
31. Quinton, J.N., Catt, J.A. and Hess, T.M. 2001. The selective removal of phosphorus from soil. Journal of Environmental Quality, 30(2): 538-545.
32. Rafahi, H.Gh. 2015. Soil Erosion by Water & Conservation. 7th edition.Tehran University Publication. 674 pp, (in Persian)
33. Rongsheng, F. and Zhanbin, L. 1993. Rainsplash and sediment transport model on the slope. Journal of Hydraulic Engineering, 6: 24-29.
34. Rubio, J. L., Forteza, J., Andreu, V. and Cerni, R. 1997. Soil profile characteristics influencing runoff and soil erosion after forest fire: a case study (Valencia, Spain). Soil Technology, 11(1): 67-78.
35. Santos, F.L., Reis, J.L., Martins, O. C., Castanheira, N.L. and Serralheiro, R.P. 2003. Comparative assessment of infiltration, runoff and erosion of sprinkler irrigated soils. Biosystems Engineering, 86(3): 355-364.
36. Shi, Z., Fang, N., Wu, F., Wang, L., Yue, B. and Wu, G. 2012. Soil erosion processes and sediment sorting associated with transport mechanisms on steep slopes. Journal of Hydrology, 454: 123-130.
37. Tan, K. H. 2005. Soil sampling, preparation, and analysis: CRC press. 75-86.
38. Thomas, G. 1996. Soil pH and soil acidity. Methods of soil analysis. Part, 3: 475-490.
39. Touma, J., Raclot, D., Al-Ali, Y., Zante, P., Hamrouni, H. and Dridi, B. 2011. In situ determination of the soil surface crust hydraulic resistance. Journal of Hydrology, 403(3): 253-260.
40. Tripathi, R. P. and Ogbazghi, W. 2016. Watershed management to enhance rainwarter conservation and crop yields in semiarid environments-A case study at Hamelmalo Agricultural College, Anseba region of Eritera. Agricultural water Management 168: 1-10.
41. USDA, S. 1972. Soil survey laboratory methods and procedures for collecting soil samples. Soil survey Investigations Rep (1).
42. Vaezi, A.R. 2014. Modeling Runoff from Semi-Arid Agricultural Lands in Northwest Iran. Pedosphere, 24(5): 595–604.
43. Vaezi, A.L., Bahrami, H., Sadeghi, H., and Mahdian, M. 2008. Modeling the USLE K-factor for calcareous soils in northwestern Iran. Geomorphology 97 (3): 414-423.
44. Vaezi, A.L., Hasanzadeh, H. and Mohammadi, M.H. 2013. Runoff variations in the soil textures samples in the plot scale under the same rainfall events. Iranian Journal of Soil and Water Research. 44(3): 243-253. (In Persian)
45. Walkly, A. and Black, I. 1982. An examination of digestion methods for determining soil organic matter and a proposed modification of the chromic and titration. Soil Science Society of America Journal, 37(2): 29-38.
46. Walling, D. 1988. Erosion and sediment yield research some recent perspectives. Journal of Hydrology, 100(1): 113-141.
47. Williams, J., Rose, C., Thorne, P., Coates, L., West, J., Harcastle, P. and Wilson, D. 1996. Observed suspended sediments in storm conditions. Coastal Engineering Proceedings, 1(25).
48. Wischmeier, W. H., & Smith, D. D. 1978. Predicting rainfall erosion losses-A guide to conservation planning. Predicting rainfall erosion losses-A guide to conservation planning.
49. Zhang, G.-H., Guo-Bin, L., Guo-Liang, W. and Yu-Xia, W. 2011. Effects of vegetation cover and rainfall intensity on sediment-bound nutrient loss, size composition and volume fractal dimension of sediment particles. Pedosphere, 21(5): 676-684.
50. Zhao, L., Liang, X. and Wu, F. 2014. Soil surface roughness change and its effect on runoff and erosion on the Loess Plateau of China. Journal of Arid Land, 6(4): 400-409.
51. Zhao, X., Huang, J., Gao, X., Wu, P. and Wang. J. 2014. Runoff features of pasture and crop slopes at different rainfall intensities, antecedent moisture contents and gradients on the Chinese Loess Plateau: A solution of rainfall simulation experiments. Catena, 119: 90-96.
CAPTCHA Image