Effect of flow discharge and median grain size on mean flow velocity under overland flow

Ali, M.; Sterk, G.; Seeger, Manuel; Stroosnijder, L.

doi:10.1016/j.jhydrol.2012.05.051

Cited by 54 publications

(26 citation statements)

References 24 publications

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“…Emmett, ; Takken and Govers, ). Although some techniques, such as magnetic velocimeters and particle imaging velocimetry, hot film anemometry, and the pulse method, are being used for the measurement of the velocity of overland flow in the laboratory under controlled conditions (Lei et al ., ), the dye‐tracing technique is generally used to estimate mean flow velocity because of its convenient application without any special instrumentation (Dunkerley, , ; Ali et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Assessing the dye‐tracer correction factor for documenting the mean velocity of sheet flow over smooth and grassed surfaces

Pan

2015

Hydrological Processes

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In the investigation of overland flow hydraulics, mean flow velocity (V) is frequently estimated using the measured surface flow velocity (Vs) multiplied by a correction factor, α. In total, 291 tests were performed in a flume with three beds [smooth glass (GL), sandpaper (SD), and plastic grass (GR)] to investigate α under submerged and non-submerged flows, and Vs was observed using dye-tracer method whilst V was calculated by the measured water depth and flow rate. For GL with 5.2% slope and 100 < Re < 5000 [Reynolds number (Re)], α ranged from 0.35 to 0.79, with an average of 0.54. For SD with slopes ranging from 2.6% to 25.9% and 300 < Re < 1200, α varied from 0.18 to 0.48 with an average of 0.32. Raindrop impacts decreased α for GL at 5.2% slope, but the effect diminished for SD as the slope increased. The α-values less than the theoretical value of 0.67 in laminar flows may be attributed to the greater spatial variability in overland flow compared with channel flow. For GR with nonsubmerged flows and Re < 4200, α varied inversely with sediment concentration (SC) at 5.2% slope but was only slightly related to SC at steep slopes of 15.6% and 25.9%. The α-values were approximately 0.8 for turbulent flows and even greater than 1.0 under high flow discharges. This finding may relate to sheet flow disturbance and retarded surface velocity due to the protruding scattered grass stems. For each surface, α varied positively with Re; α was inversely related to slope for SD but positively related to slope for GR. There was a positive relation between h and α for GL and SD but a negative relation for GR, which highlights the importance of flow inundation status to α. The inundation ratio (h/Δ) is a promising indicator for predicting α; thus, further investigations using different submerged and non-submerged surfaces are required to predict α effectively based on (h/Δ).

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Section: Introductionmentioning

confidence: 99%

Assessing the dye‐tracer correction factor for documenting the mean velocity of sheet flow over smooth and grassed surfaces

Pan

2015

Hydrological Processes

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“…Actually, in the progress of section modeling, the composition of riverbank has a great impact on the hydraulic geometry relation. Recently, some scholars have studied and analyzed the effect of median grain size 50 (Chen and Lee [18], 1996; Dade [19], 2000; Rengers and Wohl [20], 2007; Song et al [21], 2009; Ali et al [22], 2012; Navratil et al [23], 2013). Rengers and Wohl [20] (2007) found that the most significant predictor of grain size is site location because local channel width appears to strongly influence the factors of grain size.…”

Section: Introductionmentioning

confidence: 99%

“…Rengers and Wohl [20] (2007) found that the most significant predictor of grain size is site location because local channel width appears to strongly influence the factors of grain size. Ali et al [22] (2012) evaluated the dependency of mean on discharge ( ), 50 , and by regression analysis, and he found that the mean flow velocities were strongly dependent on grain size and discharge.…”

Section: Introductionmentioning

confidence: 99%

A New Model for the Regulation Width of Waterway Based on Hydraulic Geometry Relation

Zhihui

Li-chun

Zhang

et al. 2013

Mathematical Problems in Engineering

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Based on the results of the width of channel regulation on the field observations and indoor experiments, a new model of the width of channel regulation on hydraulic geometry relation was proposed and its coefficients were determined in theory in terms of the principle of dimensional analysis and multiple linear regression method in this paper. Considering the action of channel width, average flow velocity, average water depth and the slope of bed river, the median grain size 50 was introduced. Through field data were verified well, and flow gradient formulas and hydraulic formulas results were compared with more consistent ones, and it was shown that this model could better reflect relatively stable riverbed. Moreover, the established expression not only was simple and explicit, but also better laid a good theoretical basis for waterway project design. Last, taking the waterway regulation project which was from Shaoguan to Qingyuan for calculation, the results showed that new calculation method was feasible and it could be a useful reference for the design of waterway regulation. 2 0.586 50 by analyzing the data of gravel river in Canada. According to the 25 stable shoal data from the Wye Submit your manuscripts at

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“…The definition of the flow states and hydrodynamic features on vegetated slopes still deserve further study [18]. Furthermore, although many studies have investigated the flow characteristics of vegetated slopes via simulations, few studies have focused on the distribution of the velocity and turbulence characteristics along water depth for overland flow conditions, which was due to the shallow depth, unsteady state, and complex boundary conditions of such areas [19].The magnitude of the effect of vegetation on flow dynamics was found to be highly related to geometric characteristics, e.g., the vegetation type in terms of rigidity or flexibility [20,21], density [22], stem diameter [23]. In recent years, the spatial position and the distribution pattern of vegetation along a hillslope have attracted increasing attention from forest managers [5], since soil particles removed from the upper slope and re-deposited in low-lying section were physically protected against being washed away by vegetation cover at different slope positions [24].…”

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confidence: 99%

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Experimental Study of Overland Flow through Rigid Emergent Vegetation with Different Densities and Location Arrangements

Wang

Zhang

Yang

et al. 2018

Water

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The effect of vegetation density on overland flow dynamics has been extensively studied, yet fewer investigations have focused on vegetation arrangements with different densities and position features. Flume experiments were conducted to investigate the hydrodynamics of flow through rigid emergent vegetation arranged in combinations with three densities (Dense, Middle, and Sparse) and three positions (summit, backslope, and footslope). This study focused on how spatial variations regulated hydrodynamic parameters from two dimensions: direction along the slope and water depth. The total hydrodynamic parameters of bare slopes were significantly different from those of vegetated slopes. The relationship between Re and f illustrated that Re was not a unique predictor of hydraulic roughness on vegetated slopes. In the slope direction, all hydrodynamic parameters on vegetated slopes exhibited fluctuating downward/upward trends due to the clocking effect before the vegetated area and the rapid conveyance effect in the vegetated area, whereas constant values were observed on bare slopes. The performance of hydrodynamics parameters suggested that the dense rearward arrangement (SMD) was the optimal vegetation pattern to regulate flow conditions. Specifically, the vertical profiles of the velocity and turbulence features of the SMD arrangement at different sections demonstrated the significant role of vegetation density in identifying the velocity layers along the water depth. The maximum velocity and Reynolds Stress Number (RSN) indicated the position where local scour was most likely to occur, which would improve our basic understanding of the mechanisms underlying hydraulic and soil erosion processes.Thus, determining the optimum conditions for flow within vegetated slopes is vital for water and soil conservation and control.To understand the mechanisms underlying the hydraulic and soil erosion processes on vegetated hillslopes, hydrodynamic characteristics, which were mainly quantified by hydraulic parameters, e.g., water depth, mean velocity, flow pattern and resistance, kinetic energy and momentum distributions were considered as fundamental variables [6,7]. The hydrodynamic effects of emergent vegetation have been widely investigated in controlled laboratory experiments. In previous studies, well-defined rigid cylinder rods were assumed to represent an appropriate model for groups and trees or reeds and to generate accurate representations of the geometric characteristics [8]; thus, this method has been utilized as vegetation stems in numerous laboratory studies [7]. Generally, vegetation promotes the water depth [9], slows down the flow [10,11], enhances flow resistance [12], raises energy and momentum coefficients [13], attenuates the turbulence intensity [14], and promotes diffusion and deposition processes [15]. Dunkerley et al. [16] pointed out that plants could stabilize the flow state as laminar flow, whereas Hamilton et al. [17] stated that mixed flow states occurred on vegetated slopes. The definition of t...

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Effect of flow discharge and median grain size on mean flow velocity under overland flow

Cited by 54 publications

References 24 publications

Assessing the dye‐tracer correction factor for documenting the mean velocity of sheet flow over smooth and grassed surfaces

Assessing the dye‐tracer correction factor for documenting the mean velocity of sheet flow over smooth and grassed surfaces

A New Model for the Regulation Width of Waterway Based on Hydraulic Geometry Relation

Experimental Study of Overland Flow through Rigid Emergent Vegetation with Different Densities and Location Arrangements

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