Mechanisms governing incipient motion of ellipsoidal rock fragments in concentrated overland flow

2007 ◽  
Vol 14 (6) ◽  
pp. 469-480 ◽  
Author(s):  
J. W. A. Poesen ◽  
D. Torri
Keyword(s):  
Overland Flow ◽  
Incipient Motion ◽  
Rock Fragments

scholarly journals Effect of rock fragment cover on nutrient loss under varied rainfall intensities: a laboratory study

2017 ◽  
Vol 49 (2) ◽  
pp. 390-406 ◽  
Author(s):  
Hanzhi Li ◽  
Dengxing Fan ◽  
Jianzhi Niu ◽  
Guodong Jia ◽  
Jiamei Sun ◽  
...  
Keyword(s):  
Overland Flow ◽  
Northwest China ◽  
Bare Soil ◽  
Nutrient Loss ◽  
Rock Fragment ◽  
Nutrient Losses ◽  
Runoff Generation ◽  
Flow Discharge ◽  
Rock Fragments ◽  
Nutrient Conservation

Abstract Surface rock fragments retard overland flow discharge, reduce the runoff generation rate and soil erosion as well as nutrients loss. In Northwest China, a common method for minimizing water, soil, and nutrient losses is the use of rock fragment cover. We used lab stimulation testing to evaluate rock fragment cover efficacy for nutrient conservation. Nutrient losses were determined in both the runoff and sediments under three rain intensities (30, 60 and 90 mm·h−1), four rock fragment covers (0, 10, 20 and 30%) and a slope of 10°. The results showed that rock fragment cover significantly reduced the nutrient losses. Compared with the bare soil control, the rock fragment cover reduced the runoff volume and sediments by 18–38 and 11–69%, respectively, and reduced N and P losses by 9–43 and 16–70%, respectively. These results indicate that rock fragment cover is an effective method for reducing land degradation and improving local environmental conditions.

scholarly journals Soil surface roughness: comparing old and new measuring methods and application in a soil erosion model

2014 ◽  
Vol 1 (1) ◽  
pp. 981-1012 ◽  
Author(s):  
L. M. Thomsen ◽  
J. E. M. Baartman ◽  
R. J. Barneveld ◽  
T. Starkloff ◽  
J. Stolte
Keyword(s):  
Soil Erosion ◽  
Land Management ◽  
Laser Scanning ◽  
Overland Flow ◽  
Soil Surface ◽  
Depth Sensing ◽  
Catchment Scale ◽  
Erosion Model ◽  
Roller Chain ◽  
Rock Fragments

Abstract. Quantification of soil roughness, i.e. the irregularities of the soil surface due to soil texture, aggregates, rock fragments and land management, is important as it affects surface storage, infiltration, overland flow and ultimately sediment detachment and erosion. Roughness has been measured in the field using both contact methods, such as roller chain and pinboard, and sensor methods, such as stereophotogrammetry and terrestrial laser scanning (TLS). A novel depth sensing technique, originating in the gaming industry, has recently become available for earth sciences; the Xtion Pro method. Roughness data obtained using various methods are assumed to be similar; this assumption is tested in this study by comparing five different methods to measure roughness in the field on 1 m2 agricultural plots with different management (ploughing, harrowing, forest and direct seeding on stubble) in southern Norway. Subsequently, the values were used as input for the LISEM soil erosion model to test their effect on the simulated hydrograph on catchment scale. Results show that statistically significant differences between the methods were obtained only for the fields with direct drilling on stubble; for the other land management types the methods were in agreement. The spatial resolution of the contact methods was much lower than for the sensor methods (10 000 versus at least 57 000 points per m2 respectively). In terms of costs and ease of handling in the field, the Xtion Pro method is promising. Results from the LISEM model indicate that especially the roller chain underestimated the RR values and the model thereby calculated less surface runoff than measured. In conclusion: the choice of measurement method for roughness data matters and depends on the required accuracy, resolution, mobility in the field and available budget. It is recommended to use only one method within one study.

Incipient Motion Criterion for Plane Bed Channels

2009 ◽  
Vol 36 (1) ◽  
pp. 80-95
Author(s):  
Achanta Ramakrishna Rao ◽  
Bimlesh Kumar
Keyword(s):  
Incipient Motion

Algebraic Solution of the Horton-Izzard Turbulent Overland Flow Model of the Rising Hydrograph

1977 ◽  
Vol 8 (4) ◽  
pp. 249-256 ◽  
Author(s):  
Mohammad Akram Gill
Keyword(s):  
Differential Equation ◽  
Turbulent Flow ◽  
Flow Model ◽  
Overland Flow ◽  
Flow Equation ◽  
Algebraic Solution ◽  
Mixed Flow ◽  
Overland Flow Model

In the differential equation of the overland turbulent flow which was first postulated by Horton, Eq.(6), the value of c equals 5/3. For this value of c, the flow equation could not be integrated algebraically. Horton solved the equation for c = 2 and believed that his solution was valid for mixed flow. The flow equation with c = 5/3 is solved algebraically herein. It is shown elsewhere (Gill 1976) that the flow equation can indeed be integrated for any rational value of c.

Modelling of Solute Transfer to Surface Runoff

1992 ◽  
Vol 26 (7-8) ◽  
pp. 1851-1856 ◽  
Author(s):  
J. L. Lai ◽  
K. S. L. Lo
Keyword(s):  
Potassium Chloride ◽  
Surface Runoff ◽  
Laboratory Experiments ◽  
Overland Flow ◽  
Chloride Concentration ◽  
Runoff Water ◽  
Mixing Depth ◽  
Change Rate ◽  
Solute Transfer ◽  
The Media

A mixing-based model for describing solute transfer to overland flow was developed. This model included a time-dependent mixing depth of the top layer and a complete-mixed surface runoff zone. In a series of laboratory experiments, runoff was passed at various velocities and depths over a medium bed. The media were saturated with uniform concentration of potassium chloride solution. Runoff water was sampled at the beginning and end of the flume and the potassium chloride concentration analyzed. Using this model, dimensionless ultimate mixing depth and dimensionless change rate of mixing depth from experimental data were investigated and implemented. The results showed that the Reynolds number and relative roughness are two important factors.

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