References of "Erpicum, Sébastien"
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See detailMonitoring topography of laboratory fluvial dike models subjected to breaching based on a laser profilometry technique
Rifai, Ismail ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in International Symposium on River Sedimentation: Stuttgart 19th-22d september 2016 (2016, September)

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See detailSensitivity of the breaching process in the case of overtopping induced fluvial dike failure
Rifai, Ismail ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in River Flow 2016 Proceedings (2016, July)

Fluvial dikes are common structures constructed for flow channelization, prevention of river bed lateral migration and for flood protection purposes. Their aging increases their vulnerability to extreme ... [more ▼]

Fluvial dikes are common structures constructed for flow channelization, prevention of river bed lateral migration and for flood protection purposes. Their aging increases their vulnerability to extreme hydro-logical events, and subsequently may cause their failure. Many laboratory studies of overtopping induced dike failure were conducted, dealing mainly on normal configurations (i.e. dam break configuration) without ac-counting for the influence of a parallel flow. The fluvial dike breaching process remains, therefore, insuffi-ciently studied. A simplified model assuming a parameterized evolution of the breach geometry has been de-veloped to evaluate the fluvial breaching process. Results showed a sensitivity of the breaching process to the main channel configuration and to the flow conditions. Also, the evolution mode that was prescribed for the breach cross-section strongly influences the breaching duration and the sediment discharge [less ▲]

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See detailNappe Vibration Mitigation Techniques for Free-overfall Structrures
Lodomez, Maurine ULg; Crookston, Brian M.; Tullis, Blake P. et al

in Full Proceedings: Hydraulic Structures and Water System Management (2016, June 27)

Nappe vibration is a phenomenon that has been witnessed in the field for a variety of different free overflow hydraulic structures operating at low heads, such as fountains, crest gates, and weirs. This ... [more ▼]

Nappe vibration is a phenomenon that has been witnessed in the field for a variety of different free overflow hydraulic structures operating at low heads, such as fountains, crest gates, and weirs. This phenomenon is visually characterized by oscillations in the thin nappe cascading downstream of the control structure. These oscillations can produce a significant level of noise and acoustic pressure waves, which can increase the environmental and societal impacts of the hydraulic structure. As a result, a detailed investigation has been undertaken to identify practical and effective mitigation solutions for free-overfall structures where nappe vibration may be of concern. Research is being performed with a prototype-scale linear weir (weir length of 3.5 m and fall height of 3 m) located at the Engineering Hydraulics laboratory of the University of Liège, to assess the effectiveness of various crest modifications and any corresponding impacts to hydraulic efficiency (i.e., flow rate). The test matrix includes the optimization (position and spacing of elements) of three mitigation solutions which are projecting bolts, deflectors and step. In addition, a high-speed camera and audio equipment have been used to evaluate effectiveness of the configurations in reducing nappe vibration. Finally, this practical study has identified countermeasures suitable for retrofits and new construction, easy to construct, durable, hydraulically efficient, and with minimal potential for debris collection. [less ▲]

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See detailUnderground Pumped Storage Hydropower using abandoned open pit mines: influence of groundwater seepage on the system efficiency
Pujades, Estanislao ULg; Bodeux, Sarah ULg; Orban, Philippe ULg et al

Poster (2016, April)

Pumped Storage Hydropower (PSH) plants can be used to manage the production of electrical energy according to the demand. These plants allow storing and generating electricity during low and high demand ... [more ▼]

Pumped Storage Hydropower (PSH) plants can be used to manage the production of electrical energy according to the demand. These plants allow storing and generating electricity during low and high demand energy periods, respectively. Nevertheless, PSH plants require a determined topography because two reservoirs located at different heights are needed. At sites where PSH plants cannot be constructed due to topography requirements (flat regions), Underground Pumped Storage Hydropower (UPSH) plants can be used to adjust the electricity production. These plants consist in two reservoirs, the upper one is located at the surface (or at shallow depth) while the lower one is underground (or deeper). Abandoned open pit mines can be used as lower reservoirs but these are rarely isolated. As a consequence, UPSH plants will interact with surrounding aquifers exchanging groundwater. Groundwater seepage will modify hydraulic head inside the underground reservoir affecting global efficiency of the UPSH plant. The influence on the plant efficiency caused by the interaction between UPSH plants and aquifers will depend on the aquifer parameters, underground reservoir properties and pumping and injection characteristics. The alteration of the efficiency produced by the groundwater exchanges, which has not been previously considered, is now studied numerically. A set of numerical simulations are performed to establish in terms of efficiency the effects of groundwater exchanges and the optimum conditions to locate an UPSH plant. [less ▲]

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See detailDistribution of uncertainties at the municipality level for flood risk modelling along the river Meuse: implications for policy-making
Pirotton, Michel ULg; Stilmant, Frédéric; Erpicum, Sébastien ULg et al

Conference (2016, April)

Flood risk modelling has been conducted for the whole course of the river Meuse in Belgium. Major cities, such as Liege (200,000 inh.) and Namur (l 10,000 inh.), are located in the floodplains of river ... [more ▼]

Flood risk modelling has been conducted for the whole course of the river Meuse in Belgium. Major cities, such as Liege (200,000 inh.) and Namur (l 10,000 inh.), are located in the floodplains of river Meuse. Particular attention has been paid to uncertainty analysis and its implications for decision-making. The modelling chain contains flood frequency analysis, detailed 2D hydraulic computations, damage modelling and risk calculation. The relative importance of each source of uncertainty to the overall results uncertainty has been estimated by considering several alternate options for each step of the analysis; different distributions were considered in the flood frequency analysis; the influence of modelling assumptions and boundary conditions (e.g., steady vs. unsteady) were taken into account for the hydraulic computation; two different landuse classifications and two sets ofdamage functions were used; the number of exceedance probabilities involved in the risk calculation (by integration of the risk-curves) was varied. In addition, the sensitivity of the results with respect to increases in flood discharges \vas assessed. The considered increases are consistent with a "wet" climate change scenario for the time horizons 202l~2050 and 2071-2100 (Detrembleur et al., 2015). The results of hazard computation differ significantly between the upper and lower parts of the course of river Meuse in Belgium. In the former, inundation extents grow gradually as the considered flood discharge is increased (i.e. the exceedance probability is reduced), while in the downstream part, protection structures (mainly concrete walls) prevent inundation for flood discharges corresponding to exccedance probabilities of 0.01 and above (in the present climate). For higher discharges, large inundation extents are obtained in the floodplains. The highest values of risk (mean annual damage) are obtained in the municipalities which undergo relatively frequent flooding (upper part of the river), as well as in those of the downstream part of the Meuse in which flow depths in the urbanized floodplains are particularly high when inundation occurs. This is the case of the city of Liege, as a result of a subsidence process following former mining activities. For a given climate scenario, the uncertainty ranges affecting flood risk estimates are significant; but not so much that the results for the different municipalities would overlap substantially. Therefore, these uncertainties do not hamper prioritization in terms of allocation of risk reduction measures at the municipality level. In the present climate, the uncertainties arising from flood frequency analysis have a negligible influence in the upper part of the river, while they have a considerable impact on risk modelling in the lower part, where a threshold effect was observed due to the flood protection structures (sudden transition from no inundation to massive flooding when a threshold discharge is exceeded). Varying the number of exceedance probabilities in the integration of the risk curve has different effects for different municipalities; but it does not change the ranking of the municipalities in terms of flood risk. For the other scenarios, damage estimation contributes most to the overall uncertainties. As shown by this study, the magnitude of the uncertainty and its main origin vary in space and in time. This emphasizes the paramount importance of conducting distributed uncertainty analyses. In the considered study area, prioritization of risk reduction means can be reliably performed despite the modelling uncertainties. [less ▲]

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See detailThe contribution of air-fluidization to the mobility of rapid flowslides
Stilmant, Frédéric; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

Conference (2016, April)

Air-fluidization can be the origin of the long runout of gravitational flows involving fine particles such as ash. An excessive air pore pressure dramatically reduces the friction angle of the material as ... [more ▼]

Air-fluidization can be the origin of the long runout of gravitational flows involving fine particles such as ash. An excessive air pore pressure dramatically reduces the friction angle of the material as long as this pressure has not been dissipated, which occurs during the flow. This phenomenon can be modelled thanks to the 2D depth-averaged equations of mass and momentum conservation and an additional transport equation for basal pore pressure evolu- tion (Iverson and Denlinger, 2001). ln this contribution, we discuss the application of this model in relation to recent experimental results on air- fluidized flows by Roche et al. (2008) and Roche (2012). The experimental results were used to set a priori the value of the diffusion coefficient in the model, taking into account the diference of scale between the experiments and real-world applications. We also compare the model predictions against detailed observations of a well-documented historical event, the collapse of a fly-ash heap in Belgium (Stilmant et al., 2015). In particular, we analyse the influence of the different components of the model on the results (pore pressure dissipation vs. pore pressure generation). The diffusion coefficient which characterizes the dissipation of air pore pressure is found sufficiently low for maintaining a fluidized flow over hundreds of meters. The study concludes that an air-tluidization theory is consistent with the field observations. These findings are particularly interesting as they seem not in line with the mainstream acceptation in landslide modelling that air generally plays a secondary role (e.g., Legros, 2002). [less ▲]

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See detailContribution of future urbanisation expansion to flood risk changes
Bruwier, Martin ULg; Mustafa, Ahmed; Archambeau, Pierre ULg et al

Conference (2016, April)

The flood risk is expected to increase in the future due to climate change and urban development. Climate change modifies flood hazard and urban development influences exposure and vulnerability to floods ... [more ▼]

The flood risk is expected to increase in the future due to climate change and urban development. Climate change modifies flood hazard and urban development influences exposure and vulnerability to floods. While the influence of climate change on flood risk has been studied widely, the impact of urban development also needs to be considered in a sustainable flood risk management approach. The main goal of this study is the determination of the sensitivity of future flood risk to different urban devel~ opment scenarios at a relatively short-time horizon in the River Meuse basin in Wallonia (Belgium). From the different scenarios, the expected impact of urban development on flood risk is assessed. Three urban expansion scenarios are developed up to 2030 based on a coupled cellular automata (CA) and agent-based (AB) urban expansion model: (i) business-as-usual, (ii) restrictive and (m) extreme expansion scenarios. The main factor controlling these scenarios is the future urban land demand. Each urban expansion scenario is developed by considering or not high and/or medium flood hazard zones as a constraint for urban development. To assess the model's performance, it is calibrated for the Meuse River valley (Belgium) to simulate urban expansion between i990 and 2000. Calibration results are then assessed by comparing the 2000 simulated land-use map and the actual 2000 land-use map. The flood damage estimation for each urban expansion scenario is determined for five flood discharges by overlaying the inundation map resulting from a hydraulic computation and tlte urban expansion map and by using damage curves and specific prices. The hydraulic model Wolt‘2D has been extensively validated by comparisons between observations and computational results during flood event .This study focuses only on mobile and immobile prices for urban lands, which are associated to the most severe damages caused by floods along the River Meuse. These findings of this study offers tools to drive urban expansion based on numerous policies visions to mitigate future flood risk along the Meuse River. In particular, we assess the impacts on future flood risk of the prohibition of urban development in high and/or medium flood hazard zones. [less ▲]

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See detailWhen the same hydraulics conditions lead to different depositional patterns: case of an idealised delta
Peltier, Yann; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Geophysical Research Abstracts (2016, April)

Deltas are complex hydrosystems and ecosystems resulting from the interactions of a river system with a water body almost at rest. Anthropogenic factors (hydropower, flood management, development in the ... [more ▼]

Deltas are complex hydrosystems and ecosystems resulting from the interactions of a river system with a water body almost at rest. Anthropogenic factors (hydropower, flood management, development in the floodplains) lead to dramatic changes in sediment transport in the rivers and in sediment management practice. From continuous, the sediment transport becomes increasingly intermittent, with long periods of deficit in the sediment supply and short periods characterized by large supplies. Understanding how these intermittencies in the sediment supply affect the delta morphodynamics is of paramount importance for predicting the possible evolution and functioning of deltas. Deltas can reasonably be idealised as a reservoir, with an inlet channel representing the river and the sud- den enlargement of the reservoir representing the water body at rest. Using such an ideal configuration enables the assessment of the influence of individual geometric and hydraulic parameters on the depositional patterns responsible for the morphodynamic evolution of the delta. Recent literature has shown that for very similar hydraulic boundary conditions, two very different types of flow fields may develop (“straight jet” vs. “meandering jet”), leading to totally different depositional patterns. In turn, these distinct depositional patterns affect the flow itself through a two-way coupling between the hydrodynamics and the morphodynamics of the deposits. These complex processes will be discussed in the proposed presentation, based on the results of over 160 experimental tests and corresponding numerical simulations. [less ▲]

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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 detailDéveloppement d'une filière de petite hydroélectricité en Wallonie: entre expertise et opportunités
Erpicum, Sébastien ULg; Duchesne, Niels

Conference given outside the academic context (2016)

S'il y avait 3000 moulins en activité en 1900 en Wallonie, aujourd'hui il n'y en a plus qu'une centaine, constate Niels Duchesne (Administrateur-délégué, Merytherm). Doté d'un diplôme d'ingénieur ... [more ▼]

S'il y avait 3000 moulins en activité en 1900 en Wallonie, aujourd'hui il n'y en a plus qu'une centaine, constate Niels Duchesne (Administrateur-délégué, Merytherm). Doté d'un diplôme d'ingénieur électromécanicien et intéressé depuis toujours par les énergies renouvelables, ce dernier s'est spécialisé dans l'hydroélectricité avec une visée de transition énergétique. Passionné également par l'idée de donner une seconde vie à tout un patrimoine de notre région, il ne cache pas les difficultés contextuelles existantes (permis, législation, …) et plaide pour une politique davantage levier pour les potentialités offertes par cette filière. Au cours de son exposé, Niels a présenté plusieurs travaux réalisés par son bureau d'études Portfolio complété par ceux menés par le Laboratoire d'Hydraulique des constructions de l'ULg, dirigé par Sébastien Erpicum. A son tours, ce dernier a exposé les services de son laboratoire, dont la modélisation physique offre un bel outil garantissant des installations hydrauliques efficaces. A côté des considérations techniques liées aux turbines, Sébastien Erpicum a alors évoqué une série de paramètres entourant ces technologies (comme l'impact sur les poissons, l'étude de la réoxygénation des eaux, …) dont il faut tenir compte en tant que contraintes. On retiendra en tout cas que les centrales hydrauliques représentent une belle alternative et offrent une réelle solution pour des problèmes de stockage d'énergie, à une époque où notre modèle énergétique doit nécessairement évoluer. [less ▲]

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See detailAerating weir at Lom Pangar dam
Savatier, Jérémy; Lino, Michel; Erpicum, Sébastien ULg et al

Conference (2016, March)

Lom Pangar is a new dam under construction in Cameroun. Its aim is mainly flow regulation of the Sanaga River in order to improve and secure hydropower production of downstream facilities. To reduce ... [more ▼]

Lom Pangar is a new dam under construction in Cameroun. Its aim is mainly flow regulation of the Sanaga River in order to improve and secure hydropower production of downstream facilities. To reduce impact on water quality and especially on dissolved oxygen for 25 to 100 m3/s discharge, an aerating weir is going to be implemented downstream of the dam for at least the 10 first years of the dam exploitation. After site selection, preliminary studies have conducted to chose a rockfill stepped weir for technical reasons including availability of materials on the dam work site and asier decommissioning. According to literature, nappe flow is the flow regime providing most effective aeration for this type of structure and application of formulae to the discharge range and geometry of the project leads to choose 50 cm high steps to create this flow regime. The proposed solution has been tested using a 1:1 scale physical model, with the following geometry: 3 m high and 15° downstream slope. Dissolved oxygen concentration has been measured in the upstream reservoir, in the downstream collecting channel and on several steps. Aeration efficiency has been measured and the physical model has been able to validate and optimize the weir design in order to reach the water aeration objectives and limit hydraulic impacts. The works are planned beginning 2017 and water aeration will be monitored. [less ▲]

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See detailEnergy conservation properties of Ritter solution for idealized dam break flow
Dewals, Benjamin ULg; Bruwier, Martin ULg; Erpicum, Sébastien ULg et al

in Journal of Hydraulic Research (2016), 54(5), 581-585

We examine different aspects of energy conservation in the case of the analytical solution of Ritter for idealized dam break flow in a horizontal frictionless and dry channel. We detail the application of ... [more ▼]

We examine different aspects of energy conservation in the case of the analytical solution of Ritter for idealized dam break flow in a horizontal frictionless and dry channel. We detail the application of the unsteady Bernoulli equation in this case and highlight that the inertial effects cancel out when averaged over the whole flow region. We also show that the potential and kinetic contributions to the total mechanical energy in the flow region have a distinct and constant relative importance: potential energy accounts for 60 %, and kinetic energy for 40 % of the total mechanical energy. These properties of Ritter solution are rarely emphasized while they may be of practical relevance, particularly for the verification of numerical schemes with respect to their ability to ensure energy conservation. [less ▲]

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See detailPhysical modeling of an aerating stepped spillway
Erpicum, Sébastien ULg; Lodomez, Maurine ULg; Savatier, Jérémy et al

in Crookston, Brian; Tullis, Blake (Eds.) Hydraulic Structures and Water System Management (2016)

To mitigate the negative effects on the water quality in the downstream river of a projected large dam, and in particular to increase the dissolved oxygen concentration during low flow periods within the ... [more ▼]

To mitigate the negative effects on the water quality in the downstream river of a projected large dam, and in particular to increase the dissolved oxygen concentration during low flow periods within the first 10 years of dam operation, an aerating weir has been designed and tested on a physical model at the Laboratory of Engineering Hydraulics (HECE) of the Liege University. The design of the structure has been done considering data from the literature. The selected solution is a 3 m high stepped spillway designed to operate in nappe flow conditions within the range of design discharges (25 – 100 m³/s). To validate the design, a physical model representing a section of the weir at a 1:1 scale has been built and operated in the laboratory. Chemical dissolved oxygen removal technique has been applied upstream of the model to be able to measure the weir aerating efficiency. The physical model results show that the proposed structure is able to maintain, in the range of discharge in the river from 25 to 100 m³/s, a minimum 5 mg/l oxygen concentration downstream, whatever the upstream oxygen concentration. The paper presents the design process of the weir, the scale model features and the results of the validation tests on the physical model. The prototype construction will take place in 2017 and the water quality will be monitored. [less ▲]

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See detailSustainable hydraulics in the era of global change - Advances in water engineering and research
Erpicum, Sébastien ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

Book published by CRC Press (2016)

In an increasingly urbanized world, water systems must be designed and operated according to innovative standards in terms of climate adaptation, resource efficiency, sustainability and resilience. This ... [more ▼]

In an increasingly urbanized world, water systems must be designed and operated according to innovative standards in terms of climate adaptation, resource efficiency, sustainability and resilience. This grand challenge triggers unprecedented questions for hydro-environment research and engineering. Addressing these issues requires a deep understanding of basic processes in fluid mechanics, heat and mass transfer, surface and groundwater flow, among others. This book unveils latest research achievements and innovations which were presented at the 4th European Congress of IAHR in Liege (Belgium). These new developments rely on state-of-the-art modelling technologies, supported by the exponentially growing availability of data and computation power. The book will serve as a reference for professionals and decision-makers involved in various water-related sectors, such as hydraulic engineering, fluvial hydraulics, coastal engineering, water resources management and many more. [less ▲]

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See detailScale effects in physical piano key weirs models
Erpicum, Sébastien ULg; Tullis, Blake; Lodomez, Maurine ULg et al

in Journal of Hydraulic Research (2016)

With inertia and gravity representing the dominant forces for most open channel flow applications (e.g. weir flow), Froude similitude is commonly used for scaling hydraulic performance data from the model ... [more ▼]

With inertia and gravity representing the dominant forces for most open channel flow applications (e.g. weir flow), Froude similitude is commonly used for scaling hydraulic performance data from the model to prototype structures. With weir flow, as the upstream head decreases, however, the relevance of surface tension and viscosity forces can increase to the point when the model and prototype similitude is not fully achieved through Froude scaling. Such discrepancies are referred as size-scale effects, and among other things, can result in variations in the head–discharge relationship, nappe trajectory, and air entrainment. Published criteria for avoiding significant size-scale effects for free flow over linear weirs have suggested that minimal heads of ∼0.02 to 0.07m be respected, independently of the model size. In this study, the size-scale effect, minimum upstream head, and Weber number limits are investigated for four piano key weirs with geometric model scales of 1:1, 1:7, 1:15, and 1:25. [less ▲]

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See detailImpacts of urban expansion on future flood damage: A case study in the River Meuse basin, Belgium
Mustafa, Ahmed; Bruwier, Martin ULg; Teller, Jacques ULg et al

in Erpicum, Sébastien; Dewals, Benjamin; Archambeau, Pierre (Eds.) et al Sustainable Hydraulics in the Era of Global Change: Advances in Water Engineering and Research (2016)

Detailed reference viewed: 36 (15 ULg)