Modeling the impacts of cave ventilation and CO2 dynamics on speleogenesis

2020 ◽  
Author(s):  
Matthew Covington ◽  
Franci Gabrovšek
Keyword(s):  
Field Data ◽  
Numerical Models ◽  
Field Studies ◽  
Spatial And Temporal Variability ◽  
Primary Control ◽  
Dissolution Rates ◽  
Liquid Phases ◽  
Slope Sediment ◽  
Karst Systems ◽  
Longitudinal Variability

<div>Approximately 10 years worth of field observations of dissolved and gaseous CO<sub>2</sub> within caves and karst springs across a variety of settings suggest that CO<sub>2</sub> dynamics provide a first-order control on both the spatial and temporal variability in dissolution rates within karst systems. Three primary effects emerge from the field studies: 1) Changes in stream slope, sediment characteristics, and resulting CO<sub>2</sub> production and exchange can drive longitudinal variability in dissolution rates along cave streams; 2) Cave airflow patterns, and resulting cave gaseous CO<sub>2</sub> concentrations, can be the primary control on the variability of in-stream dissolution rates over storm to seasonal timescales; 3) The maturation of karst systems and resulting increases of permeability within the vadose zone can increase ventilation of the subsurface, reduce the PCO<sub>2</sub> of water flowing through cave passages, and ultimately reduce dissolution rates within these passages. While these effects are evident from the field data, it is difficult to quantify the long-term impacts of these effects on the evolution of karst systems using field data alone. The processes of CO<sub>2</sub> production, cave ventilation, and CO<sub>2</sub> exchange between gas and liquid phases have not been included in previous numerical models of speleogenesis. Here we extend existing models of speleogenesis to incorporate a suite of processes that are relevant for simulating physically realistic CO<sub>2</sub> dynamics. We use this new model to explore the impacts of ventilation and CO<sub>2</sub> exchange over timescales relevant for the evolution of karst aquifers. </div><div> </div>

F. E. J. Fry's Field Studies: Good Field Data Provoke New Questions

1990 ◽  
Vol 119 (4) ◽  
pp. 574-584 ◽  
Author(s):  
Thomas H. Whillans ◽  
Henry A. Regier ◽  
W. Jack Christie
Keyword(s):  
Field Data ◽  
Field Studies

scholarly journals Longitudinal Stress Gradients and Basal Shear Stress of a Temperate Valley Glacier

1979 ◽  
Vol 24 (90) ◽  
pp. 507-508 ◽  
Author(s):  
Robert Bindschadler
Keyword(s):  
Shear Stress ◽  
Strain Rate ◽  
Field Data ◽  
Numerical Models ◽  
Lateral Strain ◽  
Longitudinal Stress ◽  
Base Shear ◽  
Stress Gradients ◽  
Valley Glacier ◽  
Image Position

AbstractFor the first time field data from a temperate valley glacier, the Variegated Glacier, are used to investigate the behavior of longitudinal stress gradients predicted by the relation(1)whereHis the local depth, andysandybare the surface and bed elevations respectively. This equation is similar to one derived by Budd (1970) for plane strain-rate, to evaluate the importance of longitudinal stress gradients, but a shape factorfis included to account approximately for lateral strain-rate gradients. Predictive numerical models of valley glaciers require the local base shear stress to be known as accurately as possible. It has been argued on theoretical grounds that whenTis averaged over distances of more than five to ten times the depth, this term is negligible. At larger averaging scales, 2Gcan then be considered a correction to the simple geometric expression of base stress due to the presence of longitudinal stress gradients. Field data of velocity and geometry are used to evaluate the terms of Equation (1), whereτband 2Gare estimated asandat intervals of 100 m,Usis the measured surface center-line velocity,Aandnare the flow-law parameters, andis the surface longitudinal strain-rate. The expression for 2Gis an approximation proposed by Budd (1970).

scholarly journals Taking into Account both Explicit Conduits and the Unsaturated Zone in Karst Reservoir Hybrid Models: Impact on the Outlet Hydrograph

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3221
Author(s):  
Lucie Dal Soglio ◽  
Charles Danquigny ◽  
Naomi Mazzilli ◽  
Christophe Emblanch ◽  
Gérard Massonnat
Keyword(s):  
Unsaturated Zone ◽  
Numerical Models ◽  
Karst Aquifer ◽  
Hybrid Models ◽  
Model Parameters ◽  
Transit Times ◽  
The Matrix ◽  
Karst Reservoir ◽  
Karst Systems ◽  
The One

The main outlets of karst systems are springs, the hydrographs of which are largely affected by flow processes in the unsaturated zone. These processes differ between the epikarst and transmission zone on the one hand and the matrix and conduit on the other hand. However, numerical models rarely consider the unsaturated zone, let alone distinguishing its subsystems. Likewise, few models represent conduits through a second medium, and even fewer do this explicitly with discrete features. This paper focuses on the interest of hybrid models that take into account both unsaturated subsystems and discrete conduits to simulate the reservoir-scale response, especially the outlet hydrograph. In a synthetic karst aquifer model, we performed simulations for several parameter sets and showed the ability of hybrid models to simulate the overall response of complex karst aquifers. Varying parameters affect the pathway distribution and transit times, which results in a large variety of hydrograph shapes. We propose a classification of hydrographs and selected characteristics, which proves useful for analysing the results. The relationships between model parameters and hydrograph characteristics are not all linear; some of them have local extrema or threshold limits. The numerous simulations help to assess the sensitivity of hydrograph characteristics to the different parameters and, conversely, to identify the key parameters which can be manipulated to enhance the modelling of field cases.

scholarly journals Evaluation of dynamic passing gap acceptance on two-lane highways using field data

2017 ◽  
Vol 44 (11) ◽  
pp. 871-880 ◽  
Author(s):  
Udai Hassein ◽  
Maksym Diachuk ◽  
Said Easa
Keyword(s):  
Regression Models ◽  
Field Data ◽  
Field Studies ◽  
Gap Acceptance ◽  
Data Logger ◽  
Driver Behaviour ◽  
Age And Gender ◽  
Time To Collision ◽  
And Gender ◽  
Acceptance Model

Gap availability is an important element of safe passing on two-lane highways. Time gaps are used to determine passing behaviour based on human factors. In this paper, the decision whether to accept or reject an available passing gap is modelled using logistic regression technique that included driver characteristics (age and experience) and the gap size. Field studies were conducted to collect experimental data regarding passing driver behaviour. The data were collected using dual camera Car DVRs and a GPS data logger device that records the instantaneous speed and position of the three vehicles involved in the passing maneuver: passing vehicle, impeding vehicle, and opposing vehicle. Regression models that include driver age and gender (required as input to the gap acceptance model) were established for initial passing time, starting gap, ending gap, and time to collision. The gap acceptance model was implemented in Simulink and the results revealed that driver characteristics significantly affect gap acceptance decisions.

The use of Runoff and Surface Water Transport and Fate Models in the Pesticide Registration Process

1992 ◽  
Vol 6 (3) ◽  
pp. 743-748 ◽  
Author(s):  
Paul L. Zubkoff
Keyword(s):  
Surface Waters ◽  
Environmental Fate ◽  
Transport Model ◽  
Numerical Models ◽  
Chemical Properties ◽  
Chemical Characterization ◽  
Fate And Transport ◽  
Environmental Parameters ◽  
Field Studies ◽  
Chemical Application

In support of the registration and reregistration processes under FIFRA ‘88, numerical models are used to estimate the dissolved runoff and soil erosion loadings of pesticides to surface waters and the subsequent fate and transport of pesticides in the receiving waters. Uses for simulations include:1. Helping to determine whether additional studies on the fate and distribution of a candidate chemical in the environment and/or ecological effects may be needed when full chemical characterization is incomplete.2. Helping to more fully integrate data submissions of laboratory and field observations.3. Estimating probable fate and distribution of an agrochemical after a severe runoff event.4. Comparing alternative chemical application rates and methods for the same chemical/soil/crop/environmental combinations.5. Comparing different soil/crop/environmental combinations representing different geographical areas with the same chemical.6. Evaluating preliminary designs of proposed field studies.7. Gaining insight into the environmental fate of modern chemicals that are applied at 1 to 2% of the rates of older chemicals when sampling designs and analytical methods are not available.The Office of Pesticide Programs (OPP) commonly employs the SWRRB (45, 46) and PRZM (8, 9) models for runoff and EXAMS II (5), a fate and transport model, for surface waters. These three models are used in conjunction with appropriate databases for soils, chemical properties, and meteorological and other environmental parameters. Registrants are encouraged to clearly state assumptions, identify values for parameters by citation, report results of simulations with summary tables and graphics, and interpret their results in relation to current scientific disciplines.

Towards a process-based model to predict dune erosion along the Dutch Wadden coast

2012 ◽  
Vol 91 (3) ◽  
pp. 357-372 ◽  
Author(s):  
B.G. Ruessink ◽  
M. Boers ◽  
P.F.C. van Geer ◽  
A.T.M. de Bakker ◽  
A. Pieterse ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Current Knowledge ◽  
Numerical Models ◽  
Field Studies ◽  
Breaking Waves ◽  
Sand Transport ◽  
Breaking Wave ◽  
Field Observations ◽  
Erosion Model ◽  
Dune Erosion

AbstractAn equilibrium dune-erosion model is used every six years to assess the capability of the most seaward dune row on the Dutch Wadden islands to withstand a storm with a 1 in 10,000 probability for a given year. The present-day model is the culmination of numerous laboratory experiments with an initial cross-shore profile based on the central Netherlands coast. Large parts of the dune coast of the Wadden islands have substantially different dune and cross-shore profile characteristics than found along this central coast, related to the presence of tidal channels, ebb-tidal deltas, beach-plains and strong coastal curvature. This complicated coastal setting implies that the predictions of the dune-erosion model are sometimes doubtful; accordingly, a shift towards a process-based dune-erosion model has been proposed. A number of research findings based on recent laboratory and field studies highlight only few of the many challenges that need to be faced in order to develop and test such a model. Observations of turbulence beneath breaking waves indicate the need to include breaking-wave effects in sand transport equations, while current knowledge of infragravity waves, one of the main sand transporting mechanisms during severe storm conditions, is strongly challenged by laboratory and field observations on gently sloping beaches that are so typical of the Wadden islands. We argue that in-situ and remote-sensing field observations, laboratory experiments and numerical models need to be the pillars of Earth Scientific research in the Wadden Sea area to construct a meaningful process-based dune-erosion tool.

scholarly journals Effects of Instrumented Bottom Tripods on Process Measurements

2011 ◽  
Vol 28 (6) ◽  
pp. 827-837 ◽  
Author(s):  
Rodolfo Bolaños ◽  
Laurent O. Amoudry ◽  
Ken Doyle
Keyword(s):  
Field Data ◽  
Numerical Models ◽  
Three Dimensional ◽  
Wave Structure ◽  
Tidal Currents ◽  
Ocean Bottom ◽  
Sources Of Information ◽  
Wave Effect ◽  
Sea Bed ◽  
Process Measurements

Abstract The measurement and assessment of ocean bottom processes are important sources of information for understanding bedform evolution and sediment entrainment and for improving numerical models. Instrumented tripods have been used to investigate bottom boundary layer and sediment dynamics processes for several decades. In this paper, the effects of instrumented tripods on hydrodynamics and on the sea bed are investigated via numerical modeling and field data collected under moderate to strong tidal currents and mild surface waves. Under high currents, streamlines are modified and structure-induced vertical velocities are produced. To minimize this effect, a rotation of the three-dimensional current measurement under the frame is recommended. Acceleration of the flow under the frame is also significant (on the order of 10%–20%), which leads to an increase in bottom stress and can produce a large scour pit in energetic currents. Wave–structure interactions mainly increase turbulence near the frame. No significant wave effect has been observed near the bed, and scouring thus mostly relates to tidal currents.

scholarly journals FLOW COMPUTATIONS NEARBY A STORM SURGE BARRIER UNDER CONSTRUCTION WITH TWO-DIMENSIONAL NUMERICAL MODELS

1986 ◽  
Vol 1 (20) ◽  
pp. 143
Author(s):  
H.E. Klatter ◽  
J.M.C. Dijkzeul ◽  
G. Hartsuiker ◽  
L. Bijlsma
Keyword(s):  
Numerical Model ◽  
Storm Surge ◽  
Field Data ◽  
Numerical Models ◽  
Flow Patterns ◽  
Scale Model ◽  
Energy Losses ◽  
Local Energy ◽  
Two Dimensional ◽  
Physical Scale

This paper discusses the application of two-dimensional tidal models to the hydraulic research for the storm surge barrier in the Eastern Scheldt in the Netherlands. At the site of the barrier local energy losses dominate the flow. Three methods are discussed for dealing with these energy losses in a numerical model based on the long wave equations. The construction of the storm surge barrier provided extensive field data for various phases of the construction of the barrier and these field data are used as a test case for the computation at methods developed. One method is preferred since it gives good agreement between computations and field data. The two-dimensional flow patterns, the discharge and the head-difference agree well,, The results of scale model tests were also available for comparison. This comparison demonstrated that depth-averaged velocities, computed by a two-dimensional numerical model, are as accurate as values obtained from a large physical scale model. Even compicated flow patterns with local energy losses and sharp velocity gradients compared well.

scholarly journals Assessment of Climatic and Anthropogenic Controls on Bridge Deck Drainage and Sediment Removal

Water ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 3556
Author(s):  
Alexander Michalek ◽  
Admin Husic ◽  
Joshua Roundy ◽  
Amy T. Hansen
Keyword(s):  
Bridge Deck ◽  
Removal Rate ◽  
Hydraulic Testing ◽  
Primary Control ◽  
Sediment Removal ◽  
Longitudinal Slope ◽  
The Face ◽  
Hydraulic Infrastructure ◽  
Slope Sediment ◽  
Projected Changes

Bridge deck drainage is essential to prevent hydroplaning and maintain safety along major roadways. With projected changes in climate, current designs may not be sufficient and a better understanding of the primary controls (climate, bridge deck, and inlet design) on the hydraulic efficiency and sediment removal of drainage systems is needed to maintain public safety. To evaluate the controls on hydraulic drainage efficiency, 576 controlled laboratory experiments were conducted testing grate type (rectangular bar vs. curved vane) and downspout configuration (square vs. circular and 20 cm vs. 25 cm) across a range of flow rates, cross slopes, and longitudinal slopes. An additional 144 sediment erosion experiments were performed to identify controls on the removal of sediment. Hydraulic testing indicated that inflow driven by climate is a primary control on drainage efficiency and spread of water on a roadway. For anthropogenic controls, downspout opening size was found to be the primary control followed by longitudinal slope. Sediment removal results indicated that inflow regime and grate type were the primary controls on the sediment removal rate. Given that inflow, driven by climate, is a control on both hydraulic and sediment removal performance, hydraulic engineers should consider forecasted changes in rainfall intensity in their present-day drainage designs. We provide design guidance and discussion for developing a proactive approach to hydraulic infrastructure in the face of future climate uncertainty.

scholarly journals Wenn Baumwunden dazu beitragen, Steinschlagmodelle weiterzuentwickeln

2017 ◽  
Vol 168 (2) ◽  
pp. 84-91 ◽  
Author(s):  
Verena Eichenberger ◽  
Brian McArdell ◽  
Marc Christen ◽  
Daniel Trappmann ◽  
Markus Stoffel
Keyword(s):  
Field Data ◽  
Natural Hazard ◽  
Numerical Models ◽  
Jump Height ◽  
Mountainous Areas ◽  
Field Site ◽  
Different Types ◽  
Input Parameters ◽  
Terrain Parameters ◽  
The Difference

When tree scars contribute to develop rockfall models Rockfall is an often occurring natural hazard in mountainous areas. Because rocks proceed very quickly with different types of motion, and because their run-out path is influenced by several factors, the implementation of rockfall processes in numerical models is complex. This article presents the methods of visual scar identification on trees and of measuring rock deposits, to validate the accuracy of the RAMMS::Rockfall model within the active rockfall area of Meretschibach (Canton of Valais, Switzerland). Scenarios with different rock shapes and modified terrain parameters were applied to test the sensitivity of the model to these parameters. Using scans of natural rocks from the field site, which are representative in shape and volume resulted in more realistic modelled median jump heights compared to rocks of the same size (small or large), but also to standard RAMMS rocks which were quite similar in shape and volume to the scanned rocks. The best simulations resulted when the terrain type was defined as two classes softer than registered in terrain. In this case, the difference between the simulated median jump height and the height of the scars on trees was just 23 cm. These results led to improvements in the model and handbook. This study highlights the importance of precise field data to better specify input parameters for rockfall modelling.

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