Document Type : Research Article

Authors

1 Ferdowsi University of Mashhad

2 Research Center of Agriculture and Natural Resources, Fars Province

Abstract

Introduction: Soil erosion by water is one of the most widespread forms of land degradation and it has caused many undesirable consequences in last decades. On steep slopes, rill erosion is the most important type of erosion, which produces sediment and rill flow. It can be also considered as a vehicle for transporting soil particles detached from upland areas. Recent studies indicate that soil detachment rates are significantly influenced by land use. It is also known that there is a major difference between detachment rates of disturbed and natural soils (Zhang et al., 2003). Plowing rills especially in steep slopes increases sediment production. Sun et al. (2013) reported that the contribution of rill erosion in hill slope lands in china was more than 70%, which was approximately 50% of total soil erosion. In addition, measured soil loss is statistically related to hydraulic indicators such as slope, water depth, flow velocity, flow shear stress and stream power (Knapen et al., 2007). This study aims to evaluate the effects of hydraulic variables (shear stress and stream power) on spatial-temporal soil detachment rate. The focus is on the plowing rills in hillslope areas under wheat dry farming cultivation.
Materials and Methods: The study area is located in hilly slopes with the slope of 22.56% under dry farming wheat cultivation at 60 km of west of Shiraz, Iran. Top-down conventional plowing was carried out in order to create 10 meters furrows. Slope and cross sections of rills were measured throughout the experiment at 1 m intervals by rill-meter. Water was added to the top of the rills for 10 minutes and inflow rates were 10, 15 and 20 L min-1. Hydraulic parameters such as shear stress and stream power were calculated measuring rill morphology and water depth. Flow velocity and hydraulic radius along the different rill experiments were also calculated. Sediment concentrations were measured in three equal regular time and distance intervals (measurement points (MPs)), they were considered to calculate sediment detachment rate in different times and sections of each rill experiment for spatial and temporal soil detachment rate evaluation. One-way analysis of variance (ANOVA) was employed to test the significance of differences of sediment detachment rate among different treatments.
Results and Discussion: The results showed that the maximum values of shear stress and stream power were 14.07 Pa and 10.29 Wm-2 and the minimum values were 7.41 and 2.77 respectively. This research also indicated that changes in longitudinal profile of these hydraulic parameters along the rills affected the soil detachment rate values. Obtained average, minimum and maximum of the soil detachment rate were determined as 0.09, 0.02 and 0.22 kgm-2s-1, respectively. Due to Detachment-Transport Coupling mechanism, there was a significant difference between the initial and following MPs (P

Keywords

1- Abrahams A.D., Li G. 1998. Effect of saltating sediment on flow resistance and bed roughness in overland flow. Earth Surface Processes and Landforms, 23, 953-960.
2- Auerswald K., Fiener P., Dikau R. 2009. Rates of sheet and rill erosion in Germany-A meta-analysis. Geomorphology, 111, 182-193.
3- Auzet A.V., Boiffin J., Papy F., Ludwig B., Maucorps J. 1993. Rill erosion as a function of the characteristics of cultivated catchments in the north of France. Catena, 20, 41-62.
4- Bahadori N. 2014. Measuring soil loss using the roots of trees and rills and comparison with MPSIAC, M.Sc Thesis. Islamic Azad University. Arsanjan Branch.
5- Brunner G.W. 1995. HEC-RAS River Analysis System. Hydraulic Reference Manual. Version 1.0, DTIC Document.
6- Bruno C., Stefano C.D., Ferro V. 2008. Field investigation on rilling in the experimental Sparacia area, South Italy. Earth Surface Processes and Landforms, 33, 263-279.
7- Faeth P. 1994. Building the Case for Sustainable Agriculture: Policy Lessons from India, Chile and the Philippines. Environment: Science and Policy for Sustainable Development, 36, 16-39.
8- Ghebreiyessus Y., Gantzer C., Alberts E., Lentz R. 1994. Soil erosion by concentrated flow: shear stress and bulk density. Transactions of the American Society of Agricultural Engineers, 37.
9- Gilley J.E., Kottwitz E., Simanton J. 1990. Hydraulic characteristics of rills. Transactions of the American Society of Agricultural Engineers, 1899-1906
10- Gimenez R., Casali J., Grande I., Diez J., Campo M.A., Álvarez-Mozos J., and Goni M. 2012. Factors controlling sediment export in a small agricultural watershed in Navarre (Spain). Agricultural Water Management, 110, 1-8.
11- Gimenez R., Govers G. 2002. Flow detachment by concentrated flow on smooth and irregular beds. Soil Science Society of America Journal, 66, 1475-1483.
12- Govers G. 1991. Rill erosion on arable land in central Belgium: rates, controls and predictability. Catena, 18, 133-155.
13- Govers G. 1992. Relationship between discharge, velocity and flow area for rills eroding loose, non-layered materials. Earth Surface Processes and Landforms, 17, 515-528.
14- Govers G., Gimenez R., Van Oost K. 2007. Rill erosion: Exploring the relationship between experiments, modelling and field observations. Earth-Science Reviews, 84, 87-102.
15- Heimsath A.M., Dietrich W.E., Nishiizumi K., Finkel, R.C. 2001. Stochastic processes of soil production and transport: Erosion rates, topographic variation and cosmogenic nuclides in the Oregon Coast Range. Earth Surface Processes and Landforms, 26, 531-552.
16- Hessel R., Jetten V. 2007. Suitability of transport equations in modelling soil erosion for a small Loess Plateau catchment. Engineering geology, 91, 56-71.
17- Huang C.h., Laflen J.M. Bradford J.M. 1996. Evaluation of the detachment-transport coupling concept in the WEPP rill erosion equation. Soil Science Society of American Journal, 60, 734-739.
18- King K.W., Flanagan D.C., Norton L.D., and Laflen J.M. 1995. Rill erodibility parameters influenced by long-term management practices. American Society of Agricultural Engineers, 38:159-164.
19- Knapen A., Poesen J., Govers G., Gyssels G., Nachtergaele J. 2007. Resistance of soils to concentrated flow erosion: A review. Earth-Science Reviews, 80, 75-109.
20- Lal R. 2001. Soil degradation by erosion. Land degradation & development, 12, 519-539.
21- Lyle W., Smerdon E. 1965. Relation of compaction and other soil properties to erosion resistance of soils. Transactions of the American Society of Agricultural Engineers, 8, 419-422.
22- Merritt W.S., Letcher R.A., Jakeman A.J. 2003. A review of erosion and sediment transport models. Environmental Modelling & Software, 18, 761-799.
23- Morgan R.P.C., Martin L., Noble C. 1987. Soil erosion in the United Kingdom: a case study from mid-Bedfordshire. Silsoe College, Cranfield Institute of Technology. 0-63
24- Nearing M., Bradford J., Parker S. 1991. Soil detachment by shallow flow at low slopes. Soil Science Society of America Journal, 55, 339-344.
25- Nearing M., L. Norton, D. Bulgakov, G. Larionov, L. West and K. Dontsova. 1997. Hydraulics and erosion in eroding rills. Water Resources Research 33: 865-876
26- Owoputi L., Stolte W. 1995. Soil detachment in the physically based soil erosion process: a review. Transactions of the American Society of Agricultural Engineers, 38, 1099-1110.
27- Pimentel D. 2006. Soil erosion a food and environmental threat. Environment, development and sustainability, 8, 119-137.
28- Poesen J., Nachtergaele J., Verstraeten G., Valentin C. 2003. Gully erosion and environmental change importance and research needs. Catena, 50, 91-133.
29- Prosser I.P., Dietrich W.E. 1995. Field experiments on erosion by overland flow and their implication for a digital terrain model of channel initiation. Water Resources Research, 31, 2867-2876.
30- Rejman J., Brodowski R. 2005. Rill characteristics and sediment transport as a function of slope length during a storm event on loess soil. Earth Surface Processes and Landforms, 30, 231-239.
31- Rose C., Williams J., Sander G., Barry D. 1983. A mathematical model of soil erosion and deposition processes: I. Theory for a plane land element. Soil Science Society of America Journal, 47, 991-995.
32- Seeger M., Errea M.P., Beguerıa S., Arnaez J., Martı C., Garcıa-Ruiz J. 2004. Catchment soil moisture and rainfall characteristics as determinant factors for discharge/suspended sediment hysteretic loops in a small headwater catchment in the Spanish Pyrenees. Journal of Hydrology, 288, 299-311.
33- Sidorchuk A. 2005. Stochastic modelling of erosion and deposition in cohesive soils. Hydrological processes, 19, 1399-1417.
34- Sun L., Fang H., Qi D., Li J., Cai Q. 2013. A review on rill erosion process and its influencing factors. Chinese Geographical Science, 23, 389-402.
35- Takken I., Govers G. 2000. Hydraulics of interrill overland flow on rough, bare soil surfaces. Earth Surface Processes and Landforms, 25, 1387-1402.
36- Wirtz S., Seeger M., Ries J. 2010. The rill experiment as a method to approach a quantification of rill erosion process activity. Zeitschrift für Geomorphologie, 54, 47-64.
37- Wirtz S., Seeger, M., Remke A., Wengel R., Wagner J.F., Ries J.B. 2013. Do deterministic sediment detachment and transport equations adequately represent the process-interactions in eroding rills? An experimental field study. Catena, 101, 61-78.
38- Wirtz, S., Seeger, M., Ries, J.B., 2012. Field experiments for understanding and quantification of rill erosion processes. Catena, 91, 21-34.
39- Wong J.S., Freer J.E., Bates P.D., Sear D.A., Stephens E.M. 2014. Sensitivity of a hydraulic model to channel erosion uncertainty during extreme flooding. Hydrological Processes, 29, 261-279.
40- Zhang G.h., Liu B.y., Liu, G.b., He X.w., Nearing M. 2003. Detachment of undisturbed soil by shallow flow. Soil Science Society of America Journal, 67, 713-719.
CAPTCHA Image