References of "Erpicum, Sébastien"
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See detailEffective soil hydraulic conductivity predicted with the maximum power principle
Westhoff, Martijn ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

Conference (2016, April)

Drainage of water in soils happens for a large extent through preferential flowpaths, but these subsurface flowpaths are extremely difficult to observe or parameterize in hydrological models. To ... [more ▼]

Drainage of water in soils happens for a large extent through preferential flowpaths, but these subsurface flowpaths are extremely difficult to observe or parameterize in hydrological models. To potentially overcome this problem, thermodynamic optimality principles have been suggested to predict effective parametrization of these (sub-grid) structures, such as the maximum entropy production principle or the equivalent maximum power principle. These principles have been successfully applied to predict heat transfer from the Equator to the Poles, or turbulent heat fluxes between the surface and the atmosphere. In these examples, the effective flux adapts itself to its boundary condition by adapting its effective conductance through the creation of e.g. convection cells. However, flow through porous media, such as soils, can only quickly adapt its effective flow conductance by creation of preferential flowpaths, but it is unknown if this is guided by the aim to create maximum power. Here we show experimentally that this is indeed the case: In the lab, we created a hydrological analogue to the atmospheric model dealing with heat transport between Equator and poles. The experimental setup consists of two freely draining reservoirs connected with each other by a confined aquifer. By adding water to only one reservoir, a potential difference will build up until a steady state is reached. From the steady state potential difference and the observed flow through the aquifer, and effective hydraulic conductance can be determined. This observed conductance does correspond to the one maximizing power of the flux through the confined aquifer. Although this experiment is done in an idealized setting, it opens doors for better parameterizing hydrological models. Furthermore, it shows that hydraulic properties of soils are not static, but they change with changing boundary conditions. A potential limitation to the principle is that it only applies to steady state conditions. Therefore the rate of adaptation of hydraulic properties should be faster than the rate of change in boundary conditions. [less ▲]

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See detailDiscretization of the divergence formulation of the bed slope term in the shallow-water equations and consequences in terms of energy balance
Bruwier, Martin ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

in Applied Mathematical Modelling (2016)

In this research, the influence on energy balance of the discretization scheme of the divergence formulation of the bed slope term in the shallow-water equations is analysed theoretically (for a single ... [more ▼]

In this research, the influence on energy balance of the discretization scheme of the divergence formulation of the bed slope term in the shallow-water equations is analysed theoretically (for a single topographic step) and based on two numerical tests. Different values of the main parameter controlling the discretization scheme of the divergence formulation are analysed to identify the formulation which minimizes the energy variation resulting from the discretization. For a wide range of ambient Froude numbers and relative step heights, the theoretical value of the control parameter minimizing the energy variation falls within a very narrow range, which can reasonably be approximated by a single “optimal” value. This is a result of high practical relevance for the design of accurate numerical schemes, as confirmed by the results of the numerical tests. [less ▲]

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See detailCan the maximum power principle predict effective conductivities of a confined aquifer? A lab experiment
Westhoff, Martijn ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

Conference (2015, December 14)

Power can be performed by a system driven by a potential difference. From a given potential difference, the power that can be subtracted is constraint by the Carnot limit, which follows from the first and ... [more ▼]

Power can be performed by a system driven by a potential difference. From a given potential difference, the power that can be subtracted is constraint by the Carnot limit, which follows from the first and second laws of thermodynamics. If the system is such that the flux producing power (with power being the flux times its driving potential difference) also influences the potential difference, a maximum in power can be obtained as a result of the trade-off between the flux and the potential difference. This is referred to as the maximum power principle. It has already been shown that the atmosphere operates close to this maximum power limit when it comes to heat transport from the Equator to the poles, or vertically, from the surface to the atmospheric boundary layer. To reach this state of maximum power, the effective thermal conductivity of the atmosphere is adapted by the creation of convection cells. The aim of this study is to test if the soil’s effective hydraulic conductivity also adapts in such a way that it produces maximum power. However, the soil’s hydraulic conductivity adapts differently; for example by the creation of preferential flow paths. Here, this process is simulated in a lab experiment, which focuses on preferential flow paths created by piping. In the lab, we created a hydrological analogue to the atmospheric model dealing with heat transport between Equator and poles, with the aim to test if the effective hydraulic conductivity of the sand bed can be predicted with the maximum power principle. The experimental setup consists of two freely draining reservoir connected with each other by a confined aquifer. By adding water to only one reservoir, a potential difference will build up until a steady state is reached. The results will indicate whether the maximum power principle does apply for groundwater flow and how it should be applied. Because of the different way of adaptation of flow conductivity, the results differ from that of the atmosphere. [less ▲]

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See detailEssentials of actions
Cerfontaine, Benjamin ULg; Collin, Frédéric ULg; Denoël, Vincent ULg et al

Learning material (2015)

This document deals with the philosophy of safety in civil engineering structures, including loads and load combinations to be applied when designing a structure. It contains general concepts that are ... [more ▼]

This document deals with the philosophy of safety in civil engineering structures, including loads and load combinations to be applied when designing a structure. It contains general concepts that are presented and discussed as well as values for some important input data that can be used as order of magnitude in the initial phase of a project. [less ▲]

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See detailPotential damping of extreme floods in the river Meuse between Ampsin (B) and the Belgian-Dutch border
Bruwier, Martin ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

in Lenders, H.J.R.; Collas, F.P.L.; Geerling, G.W. (Eds.) et al Bridging gaps between river science, governance and management. Book of Abstracts NCR-Days 2015 (2015, October)

In the framework of the Interreg IVB project AMICE, hydraulic modelling of floods in the river Meuse was performed by coordinating existing models (Dewals et al. 2012a). The influence of climate change ... [more ▼]

In the framework of the Interreg IVB project AMICE, hydraulic modelling of floods in the river Meuse was performed by coordinating existing models (Dewals et al. 2012a). The influence of climate change scenarios was incorporated indirectly in the simulations through a transnational hydrological scenario (Drogue et al. 2010; Dewals et al. 2013). For a “wet” future climate, this scenario assumes that the peak discharge Q100 of the 100-year flood would increase by 15 % for the time horizon 2021-2050 and by 30 % for the time horizon 2071-2100. However, the design discharge currently used for planning in the Netherlands is higher than those considered to date in the AMICE project. From this perspective, it becomes relevant to analyse flood scenarios corresponding to a peak discharge above Q100+30 %, referred to hereafter as an “extreme” flood. The aim of the study is to give an appreciation of the potential damping of one extreme flood scenario along the river Meuse between Ampsin (Belgium) and the Belgian-Dutch border (Figure 1). This analysis is based on the hydraulic model WOLF 2D (Erpicum et al. 2010) applied to a coarse grid with simplifications in the schematisation. The hydraulic model WOLF 2D has been already used in several studies to simulate floods (Ernst et al. 2010; Beckers et al. 2013, Bruwier et al. 2015, Detrembleur et al. 2015). The coarsening of the grid for simulating the extreme flood scenario is necessary to preserve the computational efficiency, since both the total flood duration and the inundation extents (hence the number of grid cells) increase considerably between the Q100 + 30 % scenario considered previously and the extreme scenario considered here. [less ▲]

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See detailValidation and test cases for a free surface SPH model
Goffin, Louis ULg; Erpicum, Sébastien ULg; Dewals, Benjamin ULg et al

in Advances in hydroinformatics - Simhydro 2014 (2015, September)

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See detailPhysical modeling of lateral dike breaching due to overtopping
Rifai, Ismail; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in River, Coastal and Estuarine Morphodynamics, RCEM 2015 (2015, August)

Dikes are commonly used as defense structures for river flow channelization, protecting population and property from floods and against lateral riverbed migration. However, the aging of these structures ... [more ▼]

Dikes are commonly used as defense structures for river flow channelization, protecting population and property from floods and against lateral riverbed migration. However, the aging of these structures, combined with their increased vulnerability to extreme hydrological events may cause the dikes to breach, and subsequently to break. Furthermore, statistics show that flow overtopping is the main cause of dike failure, which emphasizes the need to understand thoroughly the process of breaching. Indeed, from a risk management perspective it is particularly important to have a detailed understanding of the mechanisms (e.g. internal erosion, overtopping erosion) underlying the formation of breaches due to overtopping and reliable information on flows passing through them. Conversely, the current knowledge of breaching mechanisms remains fragmented, especially because dike failure involves complex interactions between flows, materials of the structure, soil and foundations. The existing studies have addressed partially these interactions as the considered idealized dikes were generally homogenous, the piping erosion unaccounted for and the overtopping replicated in a dam-break like configuration. Yet, river embankments are subjected to high flow velocities parallel to the direction of the dike and to flow in the floodplain, which highly influence the shape of the breach and its evolution. The objective of the present work is to fill this gap. A laboratory experimental investigation is planned in the National Laboratory for Hydraulics and Environment (LNHE) of EDF R&D (France) and in the research group Hydraulics in Environmental and Civil Engineering (HECE) of the University of Liege (Belgium), reproducing realistic configurations of river dikes, accounting for the tangential flow in both main channel and floodplain. It enables thus the assessment of, on the one hand, the effect of the increase of the water level, and on the other hand, the influence of waves. The laboratory tests also consider the effect of a surface layer and composition of the dike core by testing different material mixtures. Geometry and composition of the idealized dikes are representative of typical field dikes, based on the similarity theory. [less ▲]

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See detailComposite hydraulic modeling to design a complex dam spillway
Erpicum, Sébastien ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

Conference (2015, July 01)

The paper presents the application of a composite hydraulic modeling approach to the rehabilitation studies of a complex dam spillway. First, a physical scale model of the existing works has been built ... [more ▼]

The paper presents the application of a composite hydraulic modeling approach to the rehabilitation studies of a complex dam spillway. First, a physical scale model of the existing works has been built and operated. It enabled to define very accurately the actual discharge capacity and to validate a numerical model of the system. Second, the numerical model has been used to rapidly test several rehabilitation solutions. Finally, the final design has been validated and optimized using the physical model. The paper shows how composite hydraulic modeling enables to combine the inherent advantages of physical and numerical modeling approaches, which are complementary, while being beneficial to the delay as well as the quality of the analysis. [less ▲]

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See detailImpacts of climate change on future flood damage on the river Meuse, with a distributed uncertainty analysis
Detrembleur, Sylvain; Stilmant, Frédéric ULg; Dewals, Benjamin ULg et al

in Natural Hazards (2015), 77(3), 1533-1549

Flood-risk assessments are an objective and quantitative basis for implementing harmonized flood mitigation policies at the basin scale. However, the generated results are subject to different sources of ... [more ▼]

Flood-risk assessments are an objective and quantitative basis for implementing harmonized flood mitigation policies at the basin scale. However, the generated results are subject to different sources of uncertainty arising from underlying assumptions, data availability and the random nature of the phenomenon. These sources of uncertainty are likely to bias conclusions because they are irregularly distributed in space. Therefore, this paper addresses the question of the influence of local features on the expected annual damage in different municipalities. Based on results generated in the frame of a transnational flood-risk-assessment project for the river Meuse (Western Europe) taking climate change into account, the paper presents an analysis of the relative contributions of different sources of uncertainty within one single administrative region (the Walloon region in Belgium, i.e. a river reach of approximately 150 km). The main sources of uncertainty are not only found to vary both from one municipality to the other and in time, but also to induce opposite effects on the computed damage. Nevertheless, practical conclusions for policy-makers can still be drawn. [less ▲]

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See detailModélisation mathématique des risques d’inondation dans le bassin liégeois suivant différents scénarios de changements climatiques et d’aménagement du territoire
Dewals, Benjamin ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

Conference (2015, June 03)

Dans une ancienne région minière, affectée par des affaissements significatifs de surface, la ville de Liège est actuellement efficacement protégée contre les crues par débordement de la Meuse grâce ... [more ▼]

Dans une ancienne région minière, affectée par des affaissements significatifs de surface, la ville de Liège est actuellement efficacement protégée contre les crues par débordement de la Meuse grâce essentiellement à une canalisation du fleuve. Une analyse prospective a été entamée, visant à évaluer la pérennité de la protection actuelle de la ville sous différents scénarios d’évolutions climatiques et d’aménagement du territoire. Prenant sa source en France et traversant la Belgique pour rejoindre son embouchure aux Pays-Bas, la Meuse ne peut être étudiée qu’en tenant compte de ce contexte transnational. C’est pourquoi, l’analyse prospective menée a été concertée à toutes les étapes non seulement avec les acteurs scientifiques et les gestionnaires de l’eau dans les régions limitrophes concernées, mais également avec des organisations représentatives de la société civile. En particulier, les scénarios climatiques retenus ainsi que les modélisations hydrauliques et hydro-économiques effectuées ont systématiquement été coordonnés, voire harmonisés, à l’échelle du bassin versant international du fleuve. Les résultats de l’analyse mettent en évidence un accroissement significatif de l’aléa inondation dans la ville de Liège à l’échéance de la fin du siècle. Ils permettent également de circonscrire le potentiel d’adaptation de la ville pour atténuer l’impact d’inondations, tant par des mesures techniques locales qu’à plus grande échelle. La portée de diverses politiques d’aménagement du territoire à Liège et au-delà a également pu être évaluée et l’analyse révèle un degré d’efficacité très contrasté selon les communes concernées. [less ▲]

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See detailA shallow-water model with depth-dependent porosity for urban flood modeling
Bruwier, Martin ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

in E-proceedings of the 36th IAHR World Congress (2015, June)

The availability of high-resolution topographic data enables the modeling of urban floods with a high level of accuracy. However, such a modelling has a poor computational efficiency. Subgrid models ... [more ▼]

The availability of high-resolution topographic data enables the modeling of urban floods with a high level of accuracy. However, such a modelling has a poor computational efficiency. Subgrid models enable to decrease the computational time by using coarse cells while preserving information from the detailed topographic data to some degree. In particular, shallow-water models with porosity constitute a subgrid model well-adapted for urban flood modeling. In this article, a new set of fully dynamic shallow-water equations with depth-dependent porosities is presented. Then, the implementation of the model is detailed and preliminary results obtained for a theoretical two-dimensional urban area are analyzed. Unlike recent works, the new model solves the fully dynamic shallow-water equations with depth-dependent and anisotropic porosities, a divergent formulation of the bed slope term, a non-staggered grid with quadrilateral cells and an efficient use of look-up tables to store the porosity relations. [less ▲]

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See detailApplication of the morphological acceleration factor in fluvial hydraulics
Dewals, Benjamin ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in E-proceedings of the 36th IAHR World Congress (2015, June)

The morphological acceleration factor (Morfac) has been widely used to speed-up morphodynamic simulations, mostly in coastal applications. The value of Morfac was generally set by trial and error and ... [more ▼]

The morphological acceleration factor (Morfac) has been widely used to speed-up morphodynamic simulations, mostly in coastal applications. The value of Morfac was generally set by trial and error and little theoretical background is available to identify an optimal value of Morfac for a given application and a target level of accuracy. In the present research, we generalize the few previous theoretical analyses regarding two main aspects. First, the range of the considered parameters (Froude number, relative roughness, transport rate …) has been considerably extended to cover typical values characterizing fluvial applications and not only coastal settings. Second, we show that the optimal value of Morfac depends greatly on the specific mathematical formulation of the flow model and on the flow regime. [less ▲]

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See detailLanduse change and future flood risk: an integrated and multi-scale approach
Dewals, Benjamin ULg; Bruwier, Martin ULg; Mohamed El Saeid Mustafa, Ahmed ULg et al

in E-proceedings of the 36th IAHR World Congress (2015, June)

The goal of this research is a better understanding of the complex interactions between landuse change and future flood risk. Landuse change is mainly driven by population growth and socio-economic ... [more ▼]

The goal of this research is a better understanding of the complex interactions between landuse change and future flood risk. Landuse change is mainly driven by population growth and socio-economic factors. It affects future flood risk by altering catchment hydrology and vulnerability in the floodplains, as well as through the feedback effect that changes in flood hazard may have on landuse evolution. The research is based on a chain of modelling tools, including: stochastic landuse change modelling, traffic modelling as well as Land-Use and Transport Interactions models, continuous hydrological modelling and efficient hydraulic modelling of floodplains inundation. The coupling of these modelling tools will allow assessing direct and indirect impacts of land use change on future flood risk, while considering the uncertainties related to each of these processes and their combinations at a 2100 time horizon. [less ▲]

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See detailDoes the soil’s effective hydraulic conductivity adapt in order to obey the Maximum Entropy Production principle? A lab experiment
Westhoff, Martijn ULg; Zehe, Erwin; Erpicum, Sébastien ULg et al

Conference (2015, April)

The Maximum Entropy Production (MEP) principle is a conjecture assuming that a medium is organized in such a way that maximum power is subtracted from a gradient driving a flux (with power being a flux ... [more ▼]

The Maximum Entropy Production (MEP) principle is a conjecture assuming that a medium is organized in such a way that maximum power is subtracted from a gradient driving a flux (with power being a flux times its driving gradient). This maximum power is also known as the Carnot limit. It has already been shown that the atmosphere operates close to this Carnot limit when it comes to heat transport from the Equator to the poles, or vertically, from the surface to the atmospheric boundary layer. To reach this state close to the Carnot limit, the effective thermal conductivity of the atmosphere is adapted by the creation of convection cells (e.g. wind). The aim of this study is to test if the soil’s effective hydraulic conductivity also adapts itself in such a way that it operates close to the Carnot limit. The big difference between atmosphere and soil is the way of adaptation of its resistance. The soil’s hydraulic conductivity is either changed by weathering processes, which is a very slow process, or by creation of preferential flow paths. In this study the latter process is simulated in a lab experiment, where we focus on the preferential flow paths created by piping. Piping is the process of backwards erosion of sand particles subject to a large pressure gradient. Since this is a relatively fast process, it is suitable for being tested in the lab. In the lab setup a horizontal sand bed connects two reservoirs that both drain freely at a level high enough to keep the sand bed always saturated. By adding water to only one reservoir, a horizontal pressure gradient is maintained. If the flow resistance is small, a large gradient develops, leading to the effect of piping. When pipes are being formed, the effective flow resistance decreases; the flow through the sand bed increases and the pressure gradient decreases. At a certain point, the flow velocity is small enough to stop the pipes from growing any further. In this steady state, the effective flow resistance of the sand bed will be compared with the theoretical optimal flow resistance obtained with the MEP principle. For this study, different magnitudes of the forcing will be tested, while also the effect of dry spells will be explored. [less ▲]

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