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See detailDynamic modelling of reservoir sedimentation in a semi-arid watershed
Adam, Nicolas; Erpicum, Sébastien ULg; Chenaoui, Bakhta et al

E-print/Working paper (2014)

Sedimentation in large reservoirs is a major issue in semi-arid regions characterized by severe seasonal water scarcity. As a contribution to improved sediment management, this study analyses the real ... [more ▼]

Sedimentation in large reservoirs is a major issue in semi-arid regions characterized by severe seasonal water scarcity. As a contribution to improved sediment management, this study analyses the real case of the reservoir of Sidi Yacoub in the north of Algeria. First, a dynamic model of the reservoir was set up and used to estimate hydraulic and sediment inflows, during the period 1990-2010, based on data recorded by the dam operator and measurements at a gauging station located downstream of the reservoir. Second, based on a statistical characterization of inflow and outflow discharges, a projection of future sedimentation was performed until 2030, using the assumption of stationarity of the statistical distributions. Third, the model was used to investigate the influence of possible climate change and to quantify the positive effects of measures to control erosion in the watershed. [less ▲]

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See detailValidation of a SPH model for free surface flows
Goffin, Louis ULg; Erpicum, Sébastien ULg; Dewals, Benjamin ULg et al

Conference (2014)

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See detailCan meandering flows in shallow rectangular reservoir be modelled with the 2D shallow water equations?
Peltier, Yann ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

E-print/Working paper (2014)

In this article, the ability of the 2D shallow water equations to model meandering flows in shallow rectangular reservoirs is discussed. Four meandering flows, of various shallowness, were modelled using ... [more ▼]

In this article, the ability of the 2D shallow water equations to model meandering flows in shallow rectangular reservoirs is discussed. Four meandering flows, of various shallowness, were modelled using the academic flow model WOLF 2D, which includes a depth-averaged k- model accounting for the horizontal and vertical turbulent length-scales. The bottom friction was modelled with the Colebrook-White formula and different roughness heights were considered. A Proper Orthogonal Decomposition (POD) was applied to the simulation results to extract the behaviour of the main structures responsible for the meandering flow. The same POD analysis was also performed for the reference experimental flow fields, obtained by Large-Scale Particle Image Velocimetry. The first two POD modes obtained from the numerical simulations assuming a smooth bottom are in good agreement with the experimental modes in terms of energy, as well as temporal and spatial variations, whatever the shallowness. In contrast, the remaining simulated modes are not well rendered. The effect of an increased roughness height in the simulations is finally discussed. It leads to an improved reproduction of the first two modes and of the following modes, except when significant viscous effects govern in the flow. [less ▲]

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See detailMeandering jets in shallow rectangular reservoir
Peltier, Yann ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in 7th International Conference in River Hydraulics, River Flow 2014 (2014)

In this article, meandering flows in a shallow rectangular reservoir are experimentally and numerically investigated. Two experiments were performed in a smooth shallow horizontal flume and the surface ... [more ▼]

In this article, meandering flows in a shallow rectangular reservoir are experimentally and numerically investigated. Two experiments were performed in a smooth shallow horizontal flume and the surface velocity fields were measured by Large-Scale PIV (LSPIV). The flow conditions were chosen in such a way that the friction regime of both flows was different. These flows were then modelled using the academic code WOLF2D, which solves the 2D shallow water equations and uses a depth-averaged k- model for modelling turbulence. The main characteristics of the measured and simulated flows were finally extracted from a Proper Orthogonal Decomposition (POD) of the surface velocity fields and depth-averaged velocity fields respectively and were compared. When the mean fluctuating kinetic energy of the considered POD mode is greater than 1×10-5 m²/s², the numerical modelling and the experiments are in good agreement whatever the friction regime of the flow. [less ▲]

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See detailClosure to “Parapet Wall Effect on Piano Key Weir Efficiency”
Erpicum, Sébastien ULg; Machiels, Olivier; Pirotton, Michel ULg et al

in Journal of Irrigation & Drainage Engineering (2014)

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See detailExperimental parametric study and design of Piano
Machiels, Olivier; Pirotton, Michel ULg; Archambeau, Pierre ULg et al

in Journal of Hydraulic Research (2014)

Piano Key Weirs are an effective solution for dam rehabilitation as well as new dam projects with a high level of hydraulic constraints. In order to improve the efficiency of their design, an experimental ... [more ▼]

Piano Key Weirs are an effective solution for dam rehabilitation as well as new dam projects with a high level of hydraulic constraints. In order to improve the efficiency of their design, an experimental study of the influence of the main geometric parameters has been performed. Thirty one configurations were tested for a wide range of discharges. The results of the study show the influence of the weir height, the keys widths and the overhangs lengths on the discharge capacity and flow characteristics. Based on hydraulic considerations, optimum values of the main geometric ratios are provided. An analytical formulation is developed to predict the discharge capacity of the weir as a function of its geometry. It shows an accuracy of 10% compared to the experimental results of this study and from other sources. [less ▲]

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See detailBi-stable flow fields and two-way couplings between flow and sedimentation in shallow reservoirs
Dewals, Benjamin ULg; Peltier, Yann ULg; Pirotton, Michel ULg et al

in 3rd IAHR Europe Congress, Book of Proceedings, Porto, Portugal, 14-16 April 2014 (2014)

Shallow reservoirs are structures commonly used in civil and environmental engineering. Recent experimental and numerical research has focused on the velocity fields and sediment deposits in rectangular ... [more ▼]

Shallow reservoirs are structures commonly used in civil and environmental engineering. Recent experimental and numerical research has focused on the velocity fields and sediment deposits in rectangular shallow reservoirs. These analyses highlighted the existence of fascinating complex flow fields and sedimentation patterns, involving bi-stable flow fields and significant two-way couplings between flow and sedimentation in such reservoirs. We review here the findings of the latest research and present on-going developments. [less ▲]

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See detailDiscussion of "Two-dimensional depth-averaged finite volume model for unsteady turbulent flows"
Erpicum, Sébastien ULg; Pirotton, Michel ULg; Archambeau, Pierre ULg et al

in Journal of Hydraulic Research (2014), 52(1), 148-150

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See detailHybride Modellierung deichbruchinduzierter Strömungen
Roger, Sebastian; Dewals, Benjamin ULg; Schüttrumpf, Holger

in Heimerl, S.; Meyer, H. (Eds.) Vorsorgender und nachsorgender Hochwasserschutz (2014)

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See detailLocal head-loss coefficient at the rectangular transition from a free-surface channel to a conduit
Van Nam, Nguyen; Archambeau, Pierre ULg; Dewals, Benjamin ULg et al

in Journal of Hydraulic Engineering (2013), 139(12), 1318-1323

Experimental tests have been performed to observe and determine, in stationary flow conditions, the local head loss at the transition from a free surface channel to a conduit. These investigations ... [more ▼]

Experimental tests have been performed to observe and determine, in stationary flow conditions, the local head loss at the transition from a free surface channel to a conduit. These investigations considered a wide range of discharge and varied dimensions and positions of a rectangular cross section conduit connected to the downstream extremity of a rectangular free surface channel. From the head loss evaluation results, simple analytical expressions to predict the local head loss coefficient value at the rectangular transition from a channel to a conduit are proposed and validated. [less ▲]

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See detailAssessing the vulnerability of sites in the East African Rift Valley to natural hazards: case study of Bujumbura, Burundi
Nibigira, Léonidas ULg; Havenith, Hans-Balder ULg; Dewals, Benjamin ULg et al

Conference (2013, November 13)

Due to the geomorphologic, structural and climatic context, the East African Rift Valley is prone to many natural hazards. The locally high density of the population contributes to related risk. As a ... [more ▼]

Due to the geomorphologic, structural and climatic context, the East African Rift Valley is prone to many natural hazards. The locally high density of the population contributes to related risk. As a result, the impacts on the habitat and infrastructures are constantly increasing. This work is based on a case study near the city of Bujumbura, which, for decades, has been affected by severe floods. Based on a study focusing on one of its rivers, the river Ntahangwa, this work tries to answer some questions related to the potential causes and ways of prevention and management of flood risk. The analysis is based on hydrological considerations while having a look at the possible mutual influences between these hydrological risks and geodynamic hazards. The methodology uses rainfall, geographic, demographic, topographic, and elevation data. Hydraulic modeling reveals the extent of the flood hazard according to its likelihood of occurrence and its sensitivity to geodynamic disturbances. This led us to propose solutions and related prevention/remediation measures. Considering the vulnerability of the population, it is clear that a change of people’s behavior is needed to reduce the total risk they’re exposed to, both with respect to the choice of construction areas and to all kinds of activities related to rivers exploitation. [less ▲]

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See detailLa facture salée des inondations - Construire en zone inondable : un risque chiffré par l'Université de Liège
de Muelenaere, Michel; Dewals, Benjamin ULg; Pirotton, Michel ULg

Article for general public (2013)

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See detailA fundamental study of the inception of motion of coarse sediments
Duma, Diana ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Proceedings of 2013 IAHR World Congress (2013, September)

This research aims to provide new knowledge about the inception of motion in rivers with coarse sediments and, possibly, macro-roughness flow regime, for which, so far, civil and environmental engineers ... [more ▼]

This research aims to provide new knowledge about the inception of motion in rivers with coarse sediments and, possibly, macro-roughness flow regime, for which, so far, civil and environmental engineers face much uncertainty in the determination of threshold hydraulic conditions for sediment transport. The threshold conditions have to be clearly defined, at the theoretical level, and well identified, in experimental tests. Therefore, a specific program of laboratory experiments has been designed. It relies on two complementary laboratory flumes of, respectively, 6m and 20m in length (discharge up to 100 l/s, slope between 0 and 4%). Three different thresholds have been defined to distinguish between the following four states: no motion, vibration of stone, local motion, and large scale motion. Based on experimental tests conducted so far in the smaller flume, velocity profile and turbulence intensity measured in quasi-uniform and non-uniform flow conditions have been correlated with the inception of motion. Flow velocity was measured using UVP transducers. In this paper, the results of a first phase of the study are presented, with the aim of validating the experimental setup, procedure and instrumentation. They focus particularly on the feasibility of collecting the relevant flow variables (shear velocity, turbulence) from a limited number of pointwise velocity measurements. [less ▲]

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See detailHydraulic modelling of the river Meuse
Dewals, Benjamin ULg; Huismans; Stilmant, Frédéric ULg et al

Conference (2013, September)

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See detailContribution of land use changes to future flood damage along the river Meuse in the Walloon region
Beckers, Arnaud ULg; Dewals, Benjamin ULg; Erpicum, Sébastien ULg et al

in Natural Hazards & Earth System Sciences (2013), 13

Managing flood risk in Europe is a critical issue because climate change is expected to increase flood hazard in many european countries. Beside climate change, land use evolution is also a key factor ... [more ▼]

Managing flood risk in Europe is a critical issue because climate change is expected to increase flood hazard in many european countries. Beside climate change, land use evolution is also a key factor influencing future flood risk. The core contribution of this paper is a new methodology to model residential land use evolution. Based on two climate scenarios (“dry” and “wet”), the method is applied to study the evolution of flood damage by 2100 along the river Meuse. Nine urbanization scenarios were developed: three of them assume a “current trend” land use evolution, leading to a significant urban sprawl, while six others assume a dense urban development, characterized by a higher density and a higher diversity of urban functions in the urbanized areas. Using damage curves, the damage estimation was performed by combining inundation maps for the present and future 100 yr flood with present and future land use maps and specific prices. According to the dry scenario, the flood discharge is expected not to increase. In this case, land use changes increase flood damages by 1–40 %, to EUR 334–462 million in 2100. In the wet scenario, the relative increase in flood damage is 540–630 %, corresponding to total damages of EUR 2.1–2.4 billion. In this extreme scenario, the influence of climate on the overall damage is 3–8 times higher than the effect of land use change. However, for seven municipalities along the river Meuse, these two factors have a comparable influence. Consequently, in the “wet” scenario and at the level of the whole Meuse valley in the Walloon region, careful spatial planning would reduce the increase in flood damage by no more than 11–23 %; but, at the level of several municipalities, more sustainable spatial planning would reduce future flood damage to a much greater degree. [less ▲]

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See detailDam break flow modelling with uncertainty analysis
Dewals, Benjamin ULg; Erpicum, Sébastien ULg; Pirotton, Michel ULg et al

in Gourbesville, Philippe; Cunge, Jean; Caignaert, Guy (Eds.) Advances in Hydroinformatics (2013)

Handling uncertainties in dam break flow modelling is of primary interest. Therefore, a procedure is presented here to conduct systematic analysis of the uncertainties resulting from the roughness ... [more ▼]

Handling uncertainties in dam break flow modelling is of primary interest. Therefore, a procedure is presented here to conduct systematic analysis of the uncertainties resulting from the roughness coefficient, the breaching hydrograph and topographic data. The flow simulations have been conducted with the model WOLF 2D developed at the University of Liege. This two-dimensional flow model is computationally too costly to perform a high number of repeated runs, as needed for Monte Carlo simulations. Therefore, a “reduced complexity model” has been set up, in the form of multidimensional Hermite polynomials. This method, developed by Isukapalli et al. (2004) and first applied to dam break flow by Niemeyer (2007), involves a reduced number of runs of the complete model to calibrate the polynomials. This paper shows the applicability and efficiency of the methodology, but it also discusses previously unreported shortcomings of the approach, together with hints to overcome them. Results of such uncertainty analysis for dam break flow modelling disclose crucial information for practical risk management. In particular, they reveal that the uncertainty ranges on maximum water depth and time of arrival of the front are not symmetric (overestimation vs. underestimation) and very unevenly distributed in space. [less ▲]

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