بررسی آزمایشگاهی اثر پوشش سنگ ریزه سطحی بر ضریب زبری، تنش برشی و تلفات خاک

نوع مقاله: مقاله پژوهشی

نویسندگان

1 استادیار گروه علوم خاک دانشگاه ارومیه

2 دانشجوی دکتری علوم خاک دانشگاه شهرکرد

3 دانشیار گروه علوم خاک پردیس کشاورزی و منابع طبیعی دانشگاه تهران

4 عضو هیات علمی پژوهشکده حفاظت خاک و آبخیزداری

چکیده

شرایط سطح خاک مانند زبری، ساختمان، پوشش گیاهی و پوشش سنگ­ریزه اهمیت زیادی در کنترل نفوذ آب به خاک، رواناب و فرسایش خاک دارد. پوشش سنگ­ریزه سطحی به طور مستقیم فرآیندهای فرسایش را به خصوص در مناطق خشک و نیمه خشک که پوشش گیاهی کمی دارند، تحت تاثیر قرار می­دهد. هدف از تحقیق حاضر، بررسی آزمایشگاهی اثر پوشش سنگ­ریزه سطحی بر میزان تلفات خاک و خصوصیات هیدرولیکی جریان نظیر ضریب زبری و تنش برشی در یک نمونه خاک لسی از استان گلستان بود. در این تحقیق، شبیه­سازی رواناب با استفاده از یک فلوم 5/0×6 متر و در شیب ثابت سه درصد انجام شد. تیمارها شامل سطوح مختلف پوشش سنگ­ریزه (­صفر، 10، 20 و 30 درصد) و دبی جریان­های سطحی (­4-10×5/0، ­4-10×1و ­4-10×5/1 مترمکعب در ثانیه) بودند. براساس نتایج، با افزایش پوشش سنگ­ریزه از صفر به 30 درصد در دبی­های جریان ­4-10×5/0، ­4-10×1و ­4-10×5/1، به ترتیب سرعت نسبی جریان 9/68، 74/67 و 9/70 درصد کاهش یافت. مقادیر ضریب زبری و تنش برشی نسبی با افزایش پوشش سنگ­ریزه به صورت خطی (99/0=R2) افزایش یافت. علاوه بر آن، با افزایش پوشش سنگ­ریزه از صفر به 30 درصد، مقدار تلفات خاک نسبی در دبی جریان­های ­4-10×5/0، ­4-10×1و ­4-10×5/1 به ترتیب 0/85، 7/83 و 6/73 درصد کاهش یافت. کاهش تلفات خاک رابطه نمایی (98/0=R2) با پوشش سنگ­ریزه را نشان داد.

کلیدواژه‌ها


عنوان مقاله [English]

Laboratory Investigation of Surface Rock Fragment Cover Effects on Roughness Coefficient, Shear Stress and Soil Loss

نویسندگان [English]

  • Farrokh Asadzadeh 1
  • Salman Mirzaee 2
  • Manoochehr Gorji 3
  • Ali Jafari-Ardakani 4
1 Assistant Professor, Department of Soil Science, Urmia University, Iran
2 PhD Student, Department of Soil Science, Shahrekord University, Shahrekord, Iran
3 Associate Professor, Department of Soil Science, University of Tehran
4 Soil Conservation and Watershed Management Research Institute, Tehran, Iran
چکیده [English]

Soil surface conditions such as roughness, structure, vegetation and rock fragment cover have very important effects on infiltration, run-off and soil erosion. Rock fragments at the soil surface directly affects soil erosion processes, particularly in arid and semiarid environments where vegetation cover is poor. The objective of the present research was to study the influence of rock fragment cover on the rate of soil loss and the hydraulic properties of flow such as roughness coefficient and shear stress in a loess soil sample from Golestan province. The investigation was conducted using a flume with 6 m length, 0.5 m width, and 3% gradient. The treatments included rock fragment covers (0, 10, 20 and 30%), and flow discharges of 0.5, 1.0 and 1.5 (10-4 m3 s-1). With increasing of rock fragment cover from 0 to 30% in flow discharges of 0.5, 1.0 and 1.5 (10-4 m3 s-1), relative velocity of water flow decreased 68.9, 67.7 and 70.9%, respectively. The value of relative roughness coefficient and shear stress increased linearly (R2=0.99) with increasing of rock fragment covers. In addition, with increasing of rock fragment cover from 0 to 30%, the rate of relative soil loss in flow discharges of 0.5, 1.0 and 1.5 (10-4 m3 s-1) decreased 85.0, 83.7 and 73.6%, respectively. Decreasing soil loss rate was related to Rock fragment cover by an exponential function (R2=0.98).
 

کلیدواژه‌ها [English]

  • Rock fragment cover
  • Roughness coefficient
  • Shear stress
  • Soil loss
References

Agassi M and Levy GJ. 1991. Stone-cover and rain intensity: Effects on infiltration, erosion and water splash. Australian Journal of Soil Research, 29: 565–575.

Allen JRL. 1994. Fundamental properties of fluids and their relation to sediment transport processes. In: Pye K (ed.). Sediment Transport and Depositional Processes, pp: 345-364.

Blake GR and Hartge KH. 1986. Bulk density. In: Klute A (ed.). Methods of Soil Analysis. Physical properties. Soil Science Society of America, Madison, Wisconsin, pp: 363–375.

Catt JA. 2001. The agricultural importance of loess. Earth Science Reviews, 54: 213-229.

Foster GR, Lan LJ, Nearing MA, Finkner SC and FlanganDC. 1989. Erosion component, in water erosion prediction project. In: Lan LJ and Nearing MA (ed.). Hillslope profile model documentation, pp: 101-112.

Fryear, DW. 1985. Soil cover and wind erosion. Transactions of the American Society of Agricultural Engineers, 28(3): 781-784.

Fu B, Chen L, Ma K, Zhou H and Wang J. 2000. The relationship between land use and oil condition in the hilly area of the loess plateau in Northern Shaanxi, China. Catena, 39: 69-78.

Govers G. 1985. Selectivity and transport capacity of thin flow in relation to rill erosion. Catena, 12: 35-49.

Gee GH and Bauder JW. 1986. Particle size analysis. In: Klute A (ed.). Methods of soil analysis. Physical properties. Soil Science Society of America, Madison, Wisconsin, 9: 383-411.

Gilley E, Finkner S, Doran J and Kottwitze E. 1990. Adsorption of bromide tracers onto sediment. Engineering in Agriculture, 6:35-38.

Li XY. 2003. Gravel–sand mulch for soil and water conservation in the semiarid loess region of Northwest China. Catena, 52: 105–127.

Li G, Abrahams AD and Atkinson JF. 1996. Correction factors in the determination of mean velocity of overland flow. Earth Surface Processes and Landforms, 21: 509–515.

Li, XY and Liu LY. 2003. Effect of gravel mulch on Aeolian dust accumulation in the semiarid region of northwest China. Soil and Tillage Research, 70:73–81.

Mandal UK, Rao KV, Mishra PK, Vittal KP, Sharma KL, Narsimlu B and Venkanna K. 2005. Soil infiltration, runoff and sediment yield from a shallow soil with varied stone cover and intensity of rain. European Journal of Soil Science, 56: 435–443.

Martinez-Zavala L, Jordan A, Bellinfante N and Gil J. 2010. Relationships between rock fragment cover and soil hydrological response in a Mediterranean environment. Soil Science and Plant Nutrition, 56: 95–104.

Nearing M, Bradford, JM and Parker SC. 1991. Soil detachment by shallow flow at low slopes. Soil Science Society of America Journal, 55: 339-344.

Nearing M, Norton LD, Bulgakov D, Larionova G, West L and Dontsova K. 1997. Hydraulics and erosion in eroding rills. Water Resourses Research, 33: 865-876.

Nelson DW and Sommers LE. 1982. Total carbon, organic carbon and organic matter. In: Miller AL and Keeney RH (ed.). Methods of soil analysis, Part 2, American Society of Agronomy, Madison, Wisconsin, pp: 539-579

Poesen J, Ingelmo-Sanchez F and Mucher H. 1990. The hydrological response of soil surfaces to rainfall as affected by cover and position of rock fragments in the top layer. Earth Surface Processes and Landforms, 15: 653–671.

Prosser IP, Dietrich WE and Stevenson J. 1995. Flow resistance and sediment transport by concentrated flow in a grassland valley. Geomorphology, 13: 73-86.

Rayment GE and Higginson FR.1992. Oxalat–extractable Fe and Al. In: Rayment GE, Higginson FR. Australian Laboratory Handbook for Soil and Water Chemical Methods. Kata Press, 22: 137-151.

Richards   LA. 1954. pH reading of saturated soil paste. United States Department of Agriculture (USDA) Handbook, pp: 132-148.

Rieke-Zapp D, Poesen J and Nearing MA. 2007. Effects of rock fragments incorporated in the soil matrix on concentrated flow hydraulics and erosion. Earth Surface Processes and Landforms, 32: 1063–1076.

Savat J and De Ploy J. 1982. Sheetwash and rill development by surface flow. In:Bryan RB and Yair A (ed.). Badland Geomorphology and Piping. pp: 231-247.

Tailong G, Quanjiu WD and Li JZ. 2010. Effect of surface stone cover on sediment and solute transport on the slope of fallow land in the semi-arid loess region of northwestern China. Soils and Sediments, 10:1200–1208.

TononI. 1999. Thresholds for incipient rilling and particle enteainment, Unpublished PhD Thesis, UtrechtUniversity, pp: 39-89.

Yao C, Lei T, Elliot WJ, McCool DK, Zhao J and Chen S. 2007. Critical Conditions for Rill Initiation. Soil and Water Division of American Society of Agricultural Engineers, 70-56.

Yu B. 2003. A Unified Framework For Water Erosion And Deposition Equations. Soil Science Society of America Journal, 67(1): 251-257.

Zang GH, Liu BY, Nearing MA, Hang CH and Zand KL. 2002. Soil detachment by shallow flow. Transactions of the American Society of Agricultural Engineers, 45: 331-357.