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:: Volume 12, Issue 40 (4-2018) ::
jwmseir 2018, 12(40): 11-22 Back to browse issues page
Flow characteristics and rill erodibility in relation to the rainfall intensity in a marl soil
Ali Reza Vaezi Dr. , Majid Foroumadi Engr.
University of Zanjan
Abstract:   (2303 Views)

Rill erosion which occurs as a result of runoff concentration on a hillslope is one of the major soil erosion types in arid and semi-arid regions especially where plant cover is poor. For this reason, understanding the factors affecting them is a high priority. Rill erodibility indicates the ease of soil particles detachment and transport by water shear force in a rill. The study was conducted to investigate the effect of rainfall intensity on the flow characteristics and rill erodibility (Kr) in a marl soil. A laboratory experiment was done in ten rainfall intensities from 10 to 100 mm.h-1 at three replications. Soil samples were taken from a semi-arid region in west of Zanjan and pureed to a flume with 0.4 m × 9 m in dimensions. Rill erodibility (Kr) was determined using the WEPP model at three artificial rills. The results showed that flow characteristics (velocity, discharge and shear stress) and rill erodibility were affected significantly by rainfall intensity (p<0.000). Threshold rainfall intensity was recognized to be 30 mm.h-1 for producing an erosive flow with 2.37×10-3 N.m-2 in shear stress and 0.018 kg.N-1s-1 in rill ertodibility (R2=0.92 , p< 0.01). Rill erodibility increased strongly with increasing rainfall intensity. This result was associated with higher disruption of soil aggregates and higher production of concentrated flow in the rills. Shear stress and flow concentration contrary to other flow characteristics increased strongly for rainfalls from 30 mm.h-1 to 60 mm.h-1 intensity and then significantly decreased due to larger increase in flow velocity and greater decrease in flow concentration. Out of the flow characteristics, flow velocity was the most important factor to explain the variation pattern of rill erodibility under the rainfall intensities, so that there was significant relationship between the two variables (R2=0.99, p< 0.001). This study indicated that the rainfall intensity is a major factor controlling the flow characteristics and rill erodibility of furrows in the marl soil.

Keywords: Concentrated flow, Flow velocity, Rainfall intensity threshold, Rill erosion
Full-Text [PDF 730 kb]   (378 Downloads)    
Type of Study: Research | Subject: Special
Received: 2016/05/17 | Accepted: 2016/10/18 | Published: 2018/03/14
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Vaezi A R, Foroumadi M. Flow characteristics and rill erodibility in relation to the rainfall intensity in a marl soil. jwmseir. 2018; 12 (40) :11-22
URL: http://jwmsei.ir/article-1-634-en.html

Volume 12, Issue 40 (4-2018) Back to browse issues page
مجله علوم ومهندسی آبخیزداری ایران Iranian Journal of Watershed Management Science and Engineering
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