scholarly journals Vegetation cover effects on sediment concentration and overland flow under artificial rainfall intensity

2021 ◽  
Vol 71 (2) ◽  
pp. 135-150
Author(s):  
Mounia Boussaadi ◽  
Liatim Mouzai
Keyword(s):  
Flow Velocity ◽  
Vegetation Cover ◽  
Rainfall Intensity ◽  
Overland Flow ◽  
Plant Cover ◽  
Sediment Concentration ◽  
Mean Flow ◽  
Artificial Rainfall ◽  
The Impact ◽  
Cover Density

Soil erosion depends on a number of factors including rainfall intensity, density of plant cover, and area cover. The objective of this study is to investigate the impact of these factors on flow velocity, overland flow regimes, sediment concentration, and absolute soil detachment. The soil used in this study was sandy remolded agricultural soil. The soil is packed in a tray of 1 m2 fixed on a slope of 3%; five different intensities were simulated under different vegetation cover (density and area). The results indicated that the overland flow velocity with vegetation cover was best described by polynomial function. The mean flow velocity varied from 0.021 to 1.244 m/s. Overland flow regime is subcritical and laminar. However, there are significant relationships between the vegetation cover density and sediment concentration and absolute soil detachment. The sediment concentration ranged from 1.38 to 5.65 kg/m3 whereas the absolute soil detachment ranged from 0.021?10-3 to 1.244?10-3 kg/m2/s. Finally, the vegetation cover presented a good protector to soil sediment from erosion.

scholarly journals Lake Evolution, Hydrodynamic Outburst Flood Modeling and Sensitivity Analysis in the Central Himalaya: A Case Study

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 237 ◽  
Author(s):  
Ashim Sattar ◽  
Ajanta Goswami ◽  
Anil. V. Kulkarni ◽  
Adam Emmer
Keyword(s):  
Flow Velocity ◽  
Hazard Assessment ◽  
Failure Time ◽  
Central Himalaya ◽  
Flow Depth ◽  
Mean Flow ◽  
Outburst Flood ◽  
Worst Case ◽  
Inundation Depth ◽  
The Impact

Climate change has led to the formation of numerous high-altitude lakes of glacial origin in the Himalaya. Safed Lake is one of the largest glacial lakes, located at an elevation 4882 m a.s.l. in the state of Uttarakhand, central Himalaya, India. A temporal analysis of the lake surface using satellite imagery shows that the lake has grown more than double its size from 0.10 km2 to 0.23 km2 over the past 50 years. In this study, we performed a hazard assessment of the lake using 1D and 2D hydrodynamic modeling. We identified the potential glacial lake outburst flood (GLOF) triggering factors and evaluated the impact of a moraine breach event of the lake on the nearest village located 16.2 km downstream of the lake. A series of dynamic simulations were performed for different scenario-models based on varied breach depths, breach widths and time of moraine failure. In a worst-case GLOF scenario where breach depth reached up to 60 m, hydrodynamic routing of the breach hydrograph along the given channel revealed inundation depth up to 5 m and flow velocities up to 3.2 m s−1 at Milam village. Considering the flat geometry of the frontal moraine, hazard assessment of the lake was performed by for different breach incision depths (30 and 15 m). In addition, the study incorporated a series of hydrodynamic routing to understand the sensitivity of GLOF to different model input parameters and terrain conditions. The sensitivity of the initial GLOF hydrograph to breach formation time (Tf) was evaluated by considering different hypothetical breach scenarios with a varied time of failure. Increases of 11.5% and 22% in the peak flooding were recorded when the moraine failure time was decreased by 15 and 30 min respectively. The two-dimensional sensitivity revealed flow velocity (m s−1) to be more sensitive to change in Manning’s N when compared to the inundation depth (m). Changes of 10.7% and 0.5% in the mean flow velocity (in m s−1) and flow depth (in m) were recorded when dN was 0.01. The flow velocity was more sensitive to the slope and the top-width of the channel when compared to the inundation depths. A regression of flow velocity versus slope gives a correlation coefficient of 0.76. GLOF flow hydraulics are sensitive to changes in terrain elevation, where flow depth and velocity vary in a similar manner.

scholarly journals Estimation of Velocity Profile in a Hyper-Concentrated Flow: a Critical Analysis of Bagnold Equation

10.29007/kd81 ◽  
2018 ◽  
Author(s):  
Donatella Termini ◽  
Antonio Fichera
Keyword(s):  
Velocity Profile ◽  
Debris Flow ◽  
Flow Velocity ◽  
Critical Analysis ◽  
Sediment Concentration ◽  
Concentrated Flow ◽  
Impact Forces ◽  
The Impact ◽  
The Vertical Distribution ◽  
Distribution Of Flow

Debris flow velocity is an important factor which influences the impact forces and runup. Due to the complexity of the phenomenon, it is difficult to define predictive methodologies. The present work reports some results of an experimental run conducted in order to investigate the velocity and sediment concentration distributions. A modified Bagnold’s approach to calculate the vertical distribution of flow velocity is presented.

scholarly journals In Vitro Red Blood Cell Segregation in Sickle Cell Anemia

2021 ◽  
Vol 9 ◽  
Author(s):  
Viviana Clavería ◽  
Philippe Connes ◽  
Luca Lanotte ◽  
Céline Renoux ◽  
Philippe Joly ◽  
...  
Keyword(s):  
Red Blood Cells ◽  
Flow Velocity ◽  
Sickle Cell ◽  
Sickle Cell Anemia ◽  
Blood Cells ◽  
Vascular Wall ◽  
Mean Flow ◽  
The Mean ◽  
The Impact ◽  
Mean Flow Velocity

Red blood cells in sickle cell anemia (sRBC) are more heterogeneous in their physical properties than healthy red blood cells, spanning adhesiveness, rigidity, density, size, and shape. sRBC with increased adhesiveness to the vascular wall would trigger vaso-occlusive like complications, a hallmark of sickle cell anemia. We investigated whether segregation occurs among sRBC flowing in micron-sized channels and tested the impact of aggregation on segregation. Two populations of sRBC of different densities were separated, labeled, and mixed again. The mixed suspension was flowed within glass capillary tubes at different pressure-drops, hematocrit, and suspending media that promoted or not cell aggregation. Observations were made at a fixed channel position. The mean flow velocity was obtained by using the cells as tracking particles, and the cell depleted layer (CDL) by measuring the distance from the cell core border to the channel wall. The labeled sRBC were identified by stopping the flow and scanning the cells within the channel section. The tube hematocrit was estimated from the number of fluorescence cells identified in the field of view. In non-aggregating media, our results showed a heterogeneous distribution of sRBC according to their density: low-density sRBC population remained closer to the center of the channel, while the densest cells segregated towards the walls. There was no impact of the mean flow velocity and little impact of hematocrit. This segregation heterogeneity could influence the ability of sRBC to adhere to the vascular wall and slow down blood flow. However, promoting aggregation inhibited segregation while CDL thickness was enhanced by aggregation, highlighting a potential protective role against vaso-occlusion in patients with sickle cell anemia.

scholarly journals Modeling Hydro-Dynamics in a Harbor Area in the Daishan Island, China

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 192 ◽  
Author(s):  
Yuting Li ◽  
Zhiyao Song ◽  
Guoqiang Peng ◽  
Xuwen Fang ◽  
Ruijie Li ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Flow Velocity ◽  
Suspended Sediment ◽  
Hydrodynamic Model ◽  
Transport Model ◽  
Measurement Data ◽  
Cross Flow ◽  
Sediment Concentration ◽  
Suspended Sediment Transport ◽  
The Impact

This study presents an incorporation and application of a two-dimensional, unstructured-grid hydrodynamic model with a suspended sediment transport module in Daishan, China. The model is verified with field measurement data from 2017: water level, flow velocities and suspended sediment concentration (SSC). In the application on the Daishan, the performance of the hydrodynamic model has been satisfactorily validated against observed variations of available measurement stations. Coupled with the hydrodynamic model, a sediment transport model has been developed and tested. The simulations agreed quantitatively with the observations. The validated model was applied to the construction of breakwaters and docks under a different plan. The model can calculate the flow field and siltation situation under different breakwater settings. After we have analyzed the impact of existing breakwater layout schemes and sediment transport, a reasonable plan will be selected. The results show that the sea area near the north of Yanwo Shan and Dongken Shan has a large flow velocity exceeding 2.0 m/s and the flow velocity within the isobath of 5 m is small, within 0.6 m/s. According to the sediment calculation, the dock project is feasible. However, the designed width of the fairway should be increased to ensure the navigation safety of the ship according to variation characteristics of cross flow velocity in channel.

scholarly journals Slope–velocity equilibrium and evolution of surface roughness on a stony hillslope

2017 ◽  
Vol 21 (6) ◽  
pp. 3221-3229 ◽  
Author(s):  
Mark A. Nearing ◽  
Viktor O. Polyakov ◽  
Mary H. Nichols ◽  
Mariano Hernandez ◽  
Li Li ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Rainfall Intensity ◽  
Overland Flow ◽  
Surface Condition ◽  
Relative Increase ◽  
Unique Function ◽  
Slope Gradient ◽  
Hydraulic Roughness ◽  
Artificial Rainfall ◽  
Discharge Rates

Abstract. Slope–velocity equilibrium is hypothesized as a state that evolves naturally over time due to the interaction between overland flow and surface morphology, wherein steeper areas develop a relative increase in physical and hydraulic roughness such that flow velocity is a unique function of overland flow rate independent of slope gradient. This study tests this hypothesis under controlled conditions. Artificial rainfall was applied to 2 m by 6 m plots at 5, 12, and 20 % slope gradients. A series of simulations were made with two replications for each treatment with measurements of runoff rate, velocity, rock cover, and surface roughness. Velocities measured at the end of each experiment were a unique function of discharge rates, independent of slope gradient or rainfall intensity. Physical surface roughness was greater at steeper slopes. The data clearly showed that there was no unique hydraulic coefficient for a given slope, surface condition, or rainfall rate, with hydraulic roughness greater at steeper slopes and lower intensities. This study supports the hypothesis of slope–velocity equilibrium, implying that use of hydraulic equations, such as Chezy and Manning, in hillslope-scale runoff models is problematic because the coefficients vary with both slope and rainfall intensity.

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

2012 ◽  
Vol 452-453 ◽  
pp. 150-160 ◽  
Author(s):  
M. Ali ◽  
G. Sterk ◽  
M. Seeger ◽  
L. Stroosnijder
Keyword(s):  
Grain Size ◽  
Flow Velocity ◽  
Overland Flow ◽  
Mean Flow ◽  
Flow Discharge ◽  
Mean Flow Velocity

scholarly journals AN ASSESSMENT OF DISTURBANCE EFFECTS ON PLANT COVER OF NUMTO NATURAL PARK (KHANTY-MANSIYSK AUTONOMOUS OKRUG - UGRA)

2020 ◽  
pp. 81-89
Author(s):  
D. V. Moskovchenko ◽  
S. P. Aref’ev ◽  
V. A. Glazunov ◽  
I. V. Filippov
Keyword(s):  
Vegetation Cover ◽  
Oil And Gas ◽  
Plant Cover ◽  
Oil Extraction ◽  
Oil Field ◽  
Nature Management ◽  
Field Development ◽  
Natural Park ◽  
Oil Deposits ◽  
The Impact

The Numto Natural Park, Khanty-Mansi Autono-mous Okrug - Yugra, Russia, has recently attracted the attention of environmental organizations due to oil extraction operations in its territory. This paper presents the study of the vegetation cover dynamics and the assessment of natural and anthropogenic disturbances of Numto’s ecosystems. Due to the development of oil deposits, more than 60 adventitious plant species arrived to the park, and the synan-thropization index reached 26.4%. Tree rings showed the predominant influence of the climatic and pyrogenic components on the growth of trees. The technogenic impact that had occurred in the 1990s gave a spasmodic increase in cedar growth in the disturbed areas in the form of abnormal hard streaks. Later on, the impact of technogenic factors on the wood growth waned. Satellite imagery helped to determine changes in the vegetation cover. From 2011 to 2018, the area of disturbed sites doubled while the length of infield roads and pipelines increased by 5.7 times. The area of burnt fire sites increased manifold; how-ever, fires occurred at a considerable distance from the oil extraction sites and were of natural origin. Currently, the disturbed ecosystems, including burnt fire sites and fire-damaged ecosystems, occupy 2.1% of the oil deposits area, and the area of pyrogenic disturbances is larger than the area of technogenic ones. Compared to the oil and gas fields in the adjacent areas, the level of disturbance in the Numto Natural Park can be considered low. Since deer pastures were not disturbed by the oil extraction operations, the traditional nature management remains possible. Further oil field development requires ongoing monitoring of the ecosystem condition.

Direct and indirect effects of a dense understory on tree seedling recruitment in temperate forests: habitat-mediated predation versus competition

2008 ◽  
Vol 38 (6) ◽  
pp. 1634-1645 ◽  
Author(s):  
Alejandro A. Royo ◽  
Walter P. Carson
Keyword(s):  
Indirect Effects ◽  
Vegetation Cover ◽  
Acer Saccharum ◽  
Resource Competition ◽  
Seedling Recruitment ◽  
Plant Cover ◽  
Acer Rubrum ◽  
Fagus Grandifolia ◽  
Tree Seedling ◽  
The Impact

In forests characterized by a dense woody and herbaceous understory layer, seedling recruitment is often directly suppressed via interspecific competition. Alternatively, these dense layers may indirectly lower tree recruitment by providing a haven for seed and seedling predators that prey on neighboring plant species. To simultaneously test for resource competition and indirect, habitat-mediated effects, we factorially manipulated understory plant cover (removed versus intact) and predation (exclosures versus controls) at three forested sites. We found that vegetation cover created privileged foraging areas that increased seed removal and seedling predation rates. Predator preference was directly related to seed size with larger seeded species including Prunus serotina Ehrh. and Fagus grandifolia Ehrh. removed more readily than smaller seeded species such as Fraxinus americana L. We found strong species-specific evidence for habitat-mediated indirect effects; establishment of P. serotina and Acer saccharum Marsh.was significantly lower under an intact hay-scented fern ( Dennstaedtia punctilobula (Michx.) T. Moore) canopy when small mammals were present. Competition also played a strong role; both P. serotina and Acer rubrum L. survival as well as A. rubrum emergence were reduced under a fern canopy with or without seed predators. The impact of habitat-mediated indirect effects and resource competition appear to vary predictably based upon predator preferences and differences in the timing of woody seed dispersal and germination relative to vegetation cover phenology. Overall, our results suggest that habitat-mediated indirect effects may be common and occur wherever vegetation provides the potential for creating privileged foraging areas.

Abstract WP88: Relationship Between Aneurysm Size and Distal Cerebral Hemodynamics

Stroke ◽  
2017 ◽  
Vol 48 (suppl_1) ◽  
Author(s):  
Ahmed E Hussein ◽  
Denise Brunozzi ◽  
Sophia F Shakur ◽  
Fady T Charbel ◽  
Ali Alaraj
Keyword(s):  
Flow Velocity ◽  
Cerebral Hemodynamics ◽  
Flow Volume ◽  
Hemodynamic Parameters ◽  
Mean Flow ◽  
Anterior Circulation ◽  
Aneurysm Size ◽  
The Impact ◽  
The Relationship ◽  
Anterior Circulation Aneurysms

Introduction: The impact of aneurysms on distal cerebral hemodynamics is unknown. Here we examine the relationship between aneurysm size and distal hemodynamics prior to treatment. Methods: Patients seen at our institution between 2006-2015 with aneurysms within the cavernous or supraclinoid ICA segment (proximal to ICA terminus) were retrospectively reviewed. Only un-ruptured proximal anterior circulation aneurysms were included, patients with contralateral aneurysms were excluded. Patients were included if they had flow volume rate and flow velocities measured prior to any treatment using Quantitative MRA. Pulsatility index (PI) = [(systolic - diastolic flow velocity)/mean flow velocity] was calculated for ipsilateral and contralateral MCA and ICA. Hemodynamic parameters were analyzed with respect to aneurysm size. Results: 42 patients were included. Mean aneurysm size was 13.5 mm (range 2-40mm). There was significant correlation (Pearson’s) between aneurysm size and ipsilateral MCA PI ( P =0.006; r=0.441), MCA ipsilateral /ICA ipsilateral PI ratio ( P =0.003; r=0.57), and MCA ipsilateral /MCA contralateral PI ratio ( P =0.008; r=0.43). Conclusions: Larger aneurysm size is significantly associated with higher ipsilateral MCA PI, demonstrating that aneurysms change distal cerebral hemodynamics. Aneurysm treatment may thus acutely change those altered hemodynamics.

scholarly journals Slope–Velocity–Equilibrium and evolution of surface roughness on a stony hillslope

2017 ◽  
Author(s):  
Mark A. Nearing ◽  
Viktor O. Polyakov ◽  
Mary H. Nichols ◽  
Mariano Hernandez ◽  
Li Li ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Rainfall Intensity ◽  
Overland Flow ◽  
Surface Condition ◽  
Relative Increase ◽  
Unique Function ◽  
Slope Gradient ◽  
Hydraulic Roughness ◽  
Artificial Rainfall ◽  
Discharge Rates

Abstract. Slope–velocity–equilibrium is hypothesized as a state that evolves naturally over time due to the interaction between overland flow and surface morphology, wherein steeper areas develop a relative increase in physical and hydraulic roughness such that flow velocity is a unique function of overland flow rate independent of slope gradient. This study tests this hypothesis under controlled conditions. Artificial rainfall was applied to 2 m by 6 m plots at 5 %, 12 %, and 20 % slope gradients. A series of simulations were made for each treatment with measurements of runoff rate, velocity, rock cover, and surface roughness. Velocities measured at the end of each experiment were a unique function of discharge rates, independent of slope gradient or rainfall intensity. Physical surface roughness was greater at steeper slopes. The data clearly showed that there was not a unique hydraulic coefficient for a given slope, surface condition, or rainfall rate, with hydraulic roughness greater at steeper slopes and lower intensities. This study supports the hypothesis of slope–velocity–equilibrium, implying that use of hydraulic equations, such as Chezy and Manning, in hillslope scale runoff models is problematic because the coefficients vary with both slope and rainfall intensity.

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