Routing overland flow through sinks and flats in interpolated raster terrain surfaces

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.

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The Role of Soil Pipes and Pipeflow in Headcut Migration Processes

10.5194/egusphere-egu2020-1875 ◽

2020 ◽

Author(s):

Ximeng Xu ◽

Glenn V. Wilson ◽

Fenli Zheng ◽

Qiuhong Tang

Keyword(s):

Shallow Water ◽

Water Table ◽

Migration Rate ◽

Overland Flow ◽

Shallow Water Table ◽

Perched Water ◽

Scour Hole ◽

Free Drainage ◽

Flow Through ◽

Soil Pipe

Headcut formation and migration is sometimes mistaken as the result of overland flow without realizing that the headcut was formed by or significantly influenced by flow through soil pipes into the headcut. To determine the effects of a soil pipe and flow through a soil pipe on headcut migration, laboratory experiments were conducted under free-drainage conditions and conditions of a shallow water table. Soil beds with a 3-cm deep initial headcut were formed in a flume with a 1.5-cm diameter soil pipe 15 cm below the bed surface. Overland flow and flow into the soil pipe was applied at a constant rate of 68 L/min and 1 L/min, respectively, at the upper end of the flume. The headcut migration rate and sediment concentrations in both surface (channel) and subsurface (soil pipe) flows were measured with time. The typical response without a soil pipe was the formation of a headcut that extended in depth until an equilibrium scour hole was established at which time the headcut migrated upslope. The presence of a soil pipe below the channel, and particularly the phenomena of flow through a soil pipe and into the headcut, whether by seepage from a shallow water table or upslope inflow, significantly impacted the headcut migration. Pipeflow caused erosion inside of the soil pipe at the same time that runoff was causing a scour hole to deepen and migrate. When the headcut extended to the depth of the soil pipe, surface runoff entering the scour hole interacted with flow from the soil pipe also entering the scour hole. This interaction dramatically altered the headcut processes, greatly accelerated the headcut migration rates and sediment concentrations. Conditions in which a perched water table provided seepage into the soil pipe in addition to pipeflow increased the sediment concentration by 42% and the headcut migration rate by 47% compared with pipeflow under free-drainage conditions. The time that overland flow converged with subsurface flow was advanced under seepage conditions by 2.3 and 5.0 minutes compared with free-drainage condition. This study confirmed that pipeflow dramatically accelerates headcut migration especially under conditions of shallow perched water tables and highlights the importance of understanding these processes in headcut migration processes.

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Effect of Microtopography, Slope Length and Gradient, and Vegetative Cover on Overland Flow through Simulation

Journal of Hydrologic Engineering ◽

10.1061/(asce)1084-0699(2004)9:5(375) ◽

2004 ◽

Vol 9 (5) ◽

pp. 375-382 ◽

Cited By ~ 62

Author(s):

Q. Q. Liu ◽

V. P. Singh

Keyword(s):

Overland Flow ◽

Vegetative Cover ◽

Slope Length ◽

Flow Through

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Simulating Climate Change Impacts on the Recharge Dynamics of a Mediterranean Karst Aquifer

10.5194/egusphere-egu2020-17009 ◽

2020 ◽

Author(s):

Lysander Bresinsky ◽

Jannes Kordilla ◽

Emanuel Thoenes ◽

Thibault Würsch ◽

Irina Engelhardt ◽

...

Keyword(s):

High Performance ◽

Overland Flow ◽

Karst Aquifer ◽

Extreme Rainfall ◽

Small Scale ◽

Surface Zone ◽

Dry Valleys ◽

Flow Through ◽

Infiltration Excess ◽

The Impact

Integrated surface-subsurface flow models solving the Richards&#8217; equation allow to simulate flow within all compartments (e.g. vadose, phreatic and surface zone) and their reciprocal interaction, and provide a useful tool to investigate the impact of climatic changes on infiltration dynamics. The Mediterranean karst aquifers are in particular prone to shifting climates, as a decrease in mean precipitation with increasing intensity and frequency of short-duration extreme rainfall, may have a significant impact on recharge dynamics and the overall water budget. Here, we use the finite element, distributed, multi-continuum flow simulator HydroGeoSphere (Aquanty, 2015) on a high-performance-computing platform to simulate infiltration and groundwater flow of the Western-Mountain-Aquifer (WMA) considering changing hydrologic conditions. A thin soil cover and abundant exposed bare karstic carbonate rock compose the recharge area, providing efficient pathways for fast direct infiltration along karst features (e.g., sinkholes and dolines). The lowered total annual precipitation may not result in a decrease in recharge since the severity and frequency of individual rainfall storms are projected to increase. To account for the duality of karst flow dynamics, both in the vadose and phreatic zones, with rapid flow through conduits and slow flow through the fractured rock matrix, we apply a double-continuum approach based on the volume-effective Richards&#8217; equation with van Genuchten parameters. A 2-D friction-based overland flow continuum, coupled via a first-order exchange term to the subsurface, accounts for overland flow due to infiltration excess. This allows to represent the partitioning of rainfall into diffuse and rapid direct recharge, e.g., along dry valleys or sinkholes. This modeling approach, therefore, accounts for complex spatially distributed infiltration characteristics of the rock-soil landscape, with focused recharge along karst features and transmission losses of ephemeral streams (wadis) under variable precipitation patterns.To get a better understanding of the complex interaction dynamics of the surface and subsurface domain in a coupled unsaturated single- and dual-continuum model we carried out small-scale process-oriented studies. Two types of synthetic karst features, (1) a dry valley averaged from field data (i.e., Wadi Natuf) and (2) an analytical generalized doline, were investigated. Geometries close to natural systems, such as sub-catchments of the WMA, were implemented. Sensitivity studies reveal complex dependencies of domain properties on linear- and log-scales. However, the exchange parameters controlling the coupling between the subsurface continua are insensitive.

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Development of apical pits in chloride cells of the gills of Pimephales promelas after chronic exposure to acid water

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100076044 ◽

1983 ◽

Vol 41 ◽

pp. 462-463

Author(s):

Richard L. Leino ◽

Jon G. Anderson ◽

J. Howard McCormick

Keyword(s):

Confidence Interval ◽

Chronic Exposure ◽

Lake Superior ◽

Pimephales Promelas ◽

Chloride Cells ◽

Fathead Minnows ◽

Secondary Lamellae ◽

Untreated Water ◽

Water Ph ◽

Flow Through

Groups of 12 fathead minnows were exposed for 129 days to Lake Superior water acidified (pH 5.0, 5.5, 6.0 or 6.5) with reagent grade H2SO4 by means of a multichannel toxicant system for flow-through bioassays. Untreated water (pH 7.5) had the following properties: hardness 45.3 ± 0.3 (95% confidence interval) mg/1 as CaCO3; alkalinity 42.6 ± 0.2 mg/1; Cl- 0.03 meq/1; Na+ 0.05 meq/1; K+ 0.01 meq/1; Ca2+ 0.68 meq/1; Mg2+ 0.26 meq/1; dissolved O2 5.8 ± 0.3 mg/1; free CO2 3.2 ± 0.4 mg/1; T= 24.3 ± 0.1°C. The 1st, 2nd and 3rd gills were subsequently processed for LM (methacrylate), TEM and SEM respectively.Three changes involving chloride cells were correlated with increasing acidity: 1) the appearance of apical pits (figs. 2,5 as compared to figs. 1, 3,4) in chloride cells (about 22% of the chloride cells had pits at pH 5.0); 2) increases in their numbers and 3) increases in the % of these cells in the epithelium of the secondary lamellae.

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