References of "Dewals, Benjamin"
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See detailExchange between drainage systems and surface flows during urban flooding: Quasi-steady and dynamic modelling in unsteady flow conditions
Kitsikoudis, Vasileios; Erpicum, Sébastien ULiege; Rubinato, Matteo et al

in Journal of Hydrology (in press)

The accurate modelling of urban flooding constitutes an integral part of flood risk assessment and management in residential and industrial areas. Interactions between drainage networks and surface runoff ... [more ▼]

The accurate modelling of urban flooding constitutes an integral part of flood risk assessment and management in residential and industrial areas. Interactions between drainage networks and surface runoff flows are commonly modelled based on weir/orifice equations; however, this approach has not been satisfactorily validated in unsteady flow conditions due to uncertainties in estimating the discharge coefficients and associated head losses. This study utilises experimental data of flow exchange between the sewer flow and the floodplain through a manhole without a lid to develop two alternate approaches that simulate this interaction and describe the associated exchange flow. A quasi-steady model links the exchange flow to the total head in the sewer pipe and the head losses in the sewer and the manhole, whilst a dynamic model takes also into account the evolution of the water level within the manhole at discrete time steps. The developed numerical models are subsequently validated against large-scale experimental data for unsteady sewer flow conditions, featuring variable exchange to the surface. Results confirmed that both models can accurately replicate experimental conditions, with improved performance when compared to existing methodologies based only on weir or orifice equations. [less ▲]

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See detailSediment management throughout the Meuse river
Barneveld, Hermjan J.; Frings, Roy M.; Dewals, Benjamin ULiege et al

Conference (2021, August)

The catchment of the Meuse River measures 34,347 km2 and is shared by France, Belgium, the Netherlands, Luxembourg and Germany. The main river is 905 km long and flows from France through Belgium and the ... [more ▼]

The catchment of the Meuse River measures 34,347 km2 and is shared by France, Belgium, the Netherlands, Luxembourg and Germany. The main river is 905 km long and flows from France through Belgium and the Netherlands towards the North Sea. Since the 19th century large engineering works have been carried out to serve navigation, power generation and flood safety. The International Meuse Commission (IMC) was established in 2002 with the signing of the Meuse Treaty (Ghent Convention). The treaty aims at achieving sustainable and integrated water management by addressing transboundary issues such as flood management, water quality and nature and water availability. In this way rules and requirements of the European Water Directive and the Floods Directive are implemented in a coordinated way. Although erosion and sedimentation processes are important for ecology as well as a potential threat for structures and navigation, the directives do not provide clear guidance for sediment management. In this research we made an inventory of sediment related problems in the countries and national sediment management strategies, which until now aim at safeguarding navigation and flood safety through maintenance dredging. However, national sediment research programs started recently including river system aspects and long-term effects of human interference and climate change. France started the program “Know the River” to understand the sediment loads, morphological development and impact of human activity and climate change. In the Netherlands the morphological system is assessed in the “Story of the Meuse”, the “Story of the Sediment” and the Integrated River Management program. In both countries the results will be used for improved management and planning new interventions. The national programs are not coordinated at this stage. This provides a challenge for international cooperation, aiming at understanding of basin wide sediment sources, sinks and fluxes and ultimately recommendations for transboundary sediment management. [less ▲]

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See detailTrying to choose the less bad route: Individual migratory behaviour of Atlantic salmon smolts (Salmo salar L.) approaching a bifurcation between a hydropower station and a navigation canal
Renardy, Séverine ULiege; Takriet, Abderrahmane ULiege; Benitez, Jean-Philippe ULiege et al

in Ecological Engineering (2021), 169

Contrary to small- and medium-sized rivers, little attention has been paid to the downstream migration of Atlantic salmon smolts in large-sized rivers and the size-related impact of hydropower stations ... [more ▼]

Contrary to small- and medium-sized rivers, little attention has been paid to the downstream migration of Atlantic salmon smolts in large-sized rivers and the size-related impact of hydropower stations. From 2014 to 2016, we investigated the downstream migration of n=72 acoustic-tagged smolts in the Meuse river at a bifurcation zone between a hydropower station equipped with three Kaplan turbines and a navigation canal. A hydrodynamic model that solves the depth-integrated shallow water equations on a Cartesian grid using a finite volume technique was used to infer the influence of water discharge and flow velocity on the smolts’ behaviour upstream of the hydroelectric complex. Of the migrating smolts, 41.5 % performed back and forth movements before approaching the complex for the first time, sometimes over long distances and at a slow pace, leading to significant delays (3‒298 h). Beyond about 250 m3 s-1, the water flow direction changes towards the hydropower station with a gradual acceleration. A median water discharge of 161 m3 s-1 and associated median flow velocity of 0.14 m s-1 tended to favour a more direct and downstream movement towards the hydropower station. On the other hand, the navigation canal was mainly approached at low water discharge (median 132 m3 s-1), due to a higher flow velocity (median 0.11 m s-1) at the entrance. Of the released smolts, only 38.6 % passed through the complex, of which 36.4 % migrated by the navigation canal and 63.6 % by the hydropower station, with a median research time of 04:44. Among all the released individuals, the escapement rate at the end of the study site was 2.9 % by the canal and 8.3 % by the Meuse river. This site, which offers two non-optimal, unattractive and unsafe migration routes, turns out to be problematic for successful downstream smolt migration. [less ▲]

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See detailExperimental test bench for performance-assessment of large submersible and dry-action pumps used in waterways
Hardy, Joris ULiege; Erpicum, Sébastien ULiege; Pirotton, Michel ULiege et al

Conference (2021, April 13)

Pumping in waterways, particularly in artificial canals, is energy-intensive, costly and may be responsible for the emission of large quantities of CO2. Innovative pumping technologies have the potential ... [more ▼]

Pumping in waterways, particularly in artificial canals, is energy-intensive, costly and may be responsible for the emission of large quantities of CO2. Innovative pumping technologies have the potential to reduce energy consumption; but their performance needs to be thoroughly as-sessed. This communication presents the design, sizing and construction of an experimental test bench for evaluating the performance of large submersible and dry-action centrifugal pumps typically used in waterways. It enables testing prototype-scale pumps and was designed in close collaboration with stakeholders such as canal operators. This experimental facility is challeng-ing on many aspects given its size, as well as requirements for power supply and for measure-ment of system efficiency. [less ▲]

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See detailEnvironmental Inequalities in Flood Exposure: A Matter of Scale
Poussard, Clémence; Dewals, Benjamin ULiege; Archambeau, Pierre ULiege et al

in Frontiers in Water (2021), 3(633046), 1-14

Studies on inequalities in exposure to flood risk have explored whether population of a lower socio-economic status are more exposed to flood hazard. While evidence exist for coastal flooding, little is ... [more ▼]

Studies on inequalities in exposure to flood risk have explored whether population of a lower socio-economic status are more exposed to flood hazard. While evidence exist for coastal flooding, little is known on inequalities for riverine floods. This paper addresses two issues: (1) is the weakest population, in socio-economic terms, more exposed to flood hazard, considering different levels of exposure to hazard? (2) Is the exposure to flood risk homogeneous across the territory, considering different scales of analysis? An analysis of the exposure of inhabitants of Liège province to flood risk was conducted at different scales (province, districts, and municipalities), considering three levels of exposure to flood hazard (level 1- low hazard, level 3- high hazard), and five socio-economic classes (class 1-poorest, class 5-wealthiest households). Our analysis confirms that weaker populations (classes 2 and 3) are usually more exposed to flood hazards than the wealthiest (classes 4 and 5). Still it should be stressed that the most precarious households (class 1) are less exposed than low to medium-range ones (classes 2 and 3). Further on the relation between socio-economic status and exposure to flood hazard varies along the spatial scale considered. At the district level, it appears that classes 4 and 5 are most exposed to flood risk in some peripheral areas. In municipalities located around the center of the city, differences of exposure to risk are not significant. [less ▲]

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See detailOccurrence and characteristic frequencies of nappe oscillations at free-overfall structures
Kitsikoudis, Vasileios ULiege; Lodomez, Maurine; Dewals, Benjamin ULiege et al

in Journal of Hydraulic Engineering (2021), 147(2),

The present study investigated the occurrence and characteristic frequency of nappe oscillations on weirs by re-analysing data from 52 experimental configurations. The considered configurations include ... [more ▼]

The present study investigated the occurrence and characteristic frequency of nappe oscillations on weirs by re-analysing data from 52 experimental configurations. The considered configurations include various shapes of the weir crest and a range of weir geometric and hydraulic characteristics with two different scales. Nappes were either confined with lateral and back walls forming a non-vented air pocket between the nappe and the weir or unconfined with atmospheric pressure everywhere around the nappe. Oscillations occurred at nappes with uniformly distributed approaching flow of low velocity and unit discharge between 0.01 and 0.06 m2/s, regardless of the model scale. Weir crests that favoured nappe oscillations had an upstream profile without geometric discontinuities. A dimensionless frequency of nappe oscillations was expressed as a power function of the ratio of fall height to the water depth at the point of detachment at the crest, separately for quarter-round and truncated half-round weir crests. The exponents of the two obtained power functions were very close to each other, which allows the usage of their average so that different weir crests exhibit solely offsetting curves. [less ▲]

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See detailOvertopping-induced failure of non–cohesive homogeneous fluvial dikes: effect of dike geometry on breach discharge and widening
Schmitz, Vincent ULiege; Erpicum, Sébastien ULiege; El Kadi Abderrezzak, Kamal et al

in Water Resources Research (2021), 57

Laboratory experiments were conducted to assess the influence of dike geometry on the breaching of non-cohesive homogeneous fluvial dikes. Both the channel-side and floodplain-side dike slopes and the ... [more ▼]

Laboratory experiments were conducted to assess the influence of dike geometry on the breaching of non-cohesive homogeneous fluvial dikes. Both the channel-side and floodplain-side dike slopes and the crest length were varied systematically. The time-evolution of the breach discharge and breach width was monitored. Dikes having a larger volume per unit width lead to a more gradual increase in breach discharge and in breach width during the first stage of breach expansion (i.e., phase of rapid erosion). In contrast, the later stage of gradual breach widening is less influenced by the dike geometry. The breach hydrographs were observed to follow three distinct patterns, which are explained based on the relative magnitude of two characteristic time scales and of a normalized form of the dike unit volume. [less ▲]

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See detailWater Soluble Polymers as a Means to Increase Flow Capacity: Field Experiment of Drag Reduction by Polymer Additives in an Irrigation Canal
Bouchenafa, Walid; Dewals, Benjamin ULiege; Lefevre, Arnaud et al

in Journal of Hydraulic Engineering (2021), 147(8), 05021003

Drag reduction method by polymer additives was tested for the first time in a large scale open-channel watercourse. Ten and a half tons of water soluble polymer were injected during 15 consecutive hours ... [more ▼]

Drag reduction method by polymer additives was tested for the first time in a large scale open-channel watercourse. Ten and a half tons of water soluble polymer were injected during 15 consecutive hours in the upstream section of an irrigation canal in permanent flow regime, leading to a 20ppm concentration of polymer in the water. The evolution of the water depth was measured every 10 min during 18 hr along ten sections further downstream, up to a distance of 26.3 km from the injection section. The water depth at all sections remained constant until the arrival of the polymer where it strongly decreased, with sometimes a slight water-depth increase beforehand, and finally remained constant as long as the polymer injection remained. A maximum of 26 cm water depth reduction (i.e. 17%) was measured at the first cross-section (2 km downstream from injection). The water depth reduction then decreased to 10% and 3% at, respectively, 10 km and 20 km downstream from the injection. However, further downstream the water depth increased by 5% at a distance of 26.3 km. The paper also discusses the environmental impacts of polymer injection through the analysis of samples taken in the water and bed material before and during the experiments. [less ▲]

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See detailApparent cohesion effects on overtopping-induced fluvial dike breaching
Rifai, Ismail; El Kadi Abderrezzak, Kamal; Hager, Willi et al

in Journal of Hydraulic Research (2021), 59(1), 75-87

Flow overtopping can lead to the initiation of breaching and failure of fluvial dikes, causing severe inundations and damage in the protected areas. For flood risk management and prevention, the accurate ... [more ▼]

Flow overtopping can lead to the initiation of breaching and failure of fluvial dikes, causing severe inundations and damage in the protected areas. For flood risk management and prevention, the accurate estimate of flow discharge across the fluvial dike breach is paramount, requiring the precise understanding of the breach expansion. Laboratory experiments were conducted to analyse the effects of fine sand, inducing apparent cohesion in the dike material, on the breach development and outflow. Tests were conducted under controlled inflow discharge and dike material composed of either homogeneous non-cohesive coarse sand or heterogeneous fine sand/coarse sand mixtures. Based on the non-intrusive Laser Profilometry technique, high temporal and spatial resolution of the three-dimensional breach geometry evolution was measured, indicating a small effect of the fine material on the overall breach dynamics. A detailed analysis revealed, however, that fine sand induces less frequent slope collapses but larger sliding/failing lumps compared to homogenous non-cohesive coarse sand. [less ▲]

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See detailPorosity Models for Large-Scale Urban Flood Modelling: a Review
Dewals, Benjamin ULiege; Bruwier, Martin ULiege; Pirotton, Michel ULiege et al

in Water (2021)

In the context of large-scale urban flood modelling, porosity shallow-water models enable a con-siderable speed-up in computations, while preserving information on subgrid topography. Over the last two ... [more ▼]

In the context of large-scale urban flood modelling, porosity shallow-water models enable a con-siderable speed-up in computations, while preserving information on subgrid topography. Over the last two decades, major improvements have been brought to these models; but a single gen-erally accepted model formulation has not yet been reached. Instead, existing models vary in many respects. Some studies define porosity parameters at the scale of the computational cells or cell interfaces, while others treat the urban area as a continuum and introduce statistical-ly-defined porosity parameters. The porosity parameters are considered either isotropic or aniso-tropic, and depth-independent or depth-dependent. The underlying flow models are based either on the full shallow-water equations, or on approximations thereof, with various parametrizations of flow resistance. Here, we provide a review of the spectrum of porosity models developed so far for large scale urban flood modelling. [less ▲]

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See detailBehind the scenes of streamflow model performance
Bouaziz, Laurène J. E.; Fenicia, Fabrizio; Thirel, Guillaume et al

in Hydrology and Earth System Sciences (2021), 25(2), 10691095

Streamflow is often the only variable used to evaluate hydrological models. In a previous international comparison study, eight research groups followed an identical protocol to calibrate twelve ... [more ▼]

Streamflow is often the only variable used to evaluate hydrological models. In a previous international comparison study, eight research groups followed an identical protocol to calibrate twelve hydrological models using observed streamflow of catchments within the Meuse basin. In the current study, we quantify the differences in five states and fluxes of these twelve process-based models with similar streamflow performance, in a systematic and comprehensive way. Next, we assess model behavior plausibility by ranking 5 the models for a set of criteria using streamflow and remote sensing data of evaporation, snow cover, soil moisture and total storage anomalies. We found substantial dissimilarities between models for annual interception and seasonal evaporation rates, the annual number of days with water stored as snow, the mean annual maximum snow storage and the size of the root-zone storage capacity. These differences in internal process representation imply that these models cannot all simultaneously be close to reality. Modeled annual evaporation rates are consistent with GLEAM estimates. However, there is a large uncertainty in modeled and remote sensing annual interception. Substantial differences are also found between MODIS and modeled number of days with snow storage. Models with relatively small root-zone storage capacities and without root water uptake reduction under dry conditions tend to have an empty root-zone storage for several days each summer, while this is not suggested by remote sensing data of evaporation, soil moisture and vegetation indices. On the other hand, models with relatively large root-zone storage capacities tend to overestimate very dry total storage anomalies of GRACE. None of the models is systematically consistent with the information available from all different (remote sensing) data sources. Yet, we did not reject models given the uncertainties in these data sources and their changing relevance for the system under investigation. [less ▲]

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See detailAssessment of lumped physically-based numerical models of dyke breaching
Schmitz, Vincent ULiege; Wylock, Grégoire; El Kadi Abderrezzak, Kamal et al

in Geophysical Research Abstracts (2021)

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See detailThermodynamic optimality principles in Earth sciences
Schymanski, Stanislaus J.; Dewals, Benjamin ULiege; Dijkstra, Henk A. et al

in Geophysical Research Abstracts (2021)

Ecohydrological systems are a result of long-term co-evolution of soils, biota and atmospheric conditions, and often respond to perturbations in non-intuitive ways. Their short-term responses can be ... [more ▼]

Ecohydrological systems are a result of long-term co-evolution of soils, biota and atmospheric conditions, and often respond to perturbations in non-intuitive ways. Their short-term responses can be explained and sometimes predicted if we understand the underlying dynamic processes and if we can observe the initial state precisely enough. However, how do they co-evolve in the long-term after a change in the boundary conditions? In 1922, Alfred Lotka hypothesised that the natural selection governing the evolution of biota and composition of ecosystems may be obeying some thermodynamic principles related to maximising energy flow through these systems. Similar thoughts have been formulated for various components of the Earth system and individual processes, such as heat transport in the atmosphere and oceans, erosion and sediment transport in river systems and estuaries, the formation of vegetation patterns, and many others. Different thermodynamic optimality principles have been applied to predict or explain a given system property or behaviour, of which the maximum entropy production and the maximum power principles are most widespread. However, the different studies did not use a common systematic approach for the formulation of the relevant system boundaries, state variables and exchange fluxes, resulting in considerable ambiguity about the application of thermodynamic optimality principles in the scientific community. Such a systematic framework has been developed recently and can be tested online at: https://renkulab.io/projects/stanislaus.schymanski/thermodynamic_optimality_blueprint In the present study, we illustrate how such a common framework can be used to classify and compare different applications of thermodynamic optimality principles in the literature, and discuss the insights gained and key criteria for a more rigorous testing of such principles. [less ▲]

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See detailModélisation hydraulique 2D pour la détermination des zones inondables
Archambeau, Pierre ULiege; Erpicum, Sébastien ULiege; Dewals, Benjamin ULiege et al

Scientific conference (2020, November 09)

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See detailAge of Water Particles as a Diagnosis of Steady-state Flows in Shallow Rectangular Reservoirs
Dewals, Benjamin ULiege; Archambeau, Pierre ULiege; Bruwier, Martin ULiege et al

in Water (2020), (12), 2819

The age of a water particle in a shallow man-made reservoir is defined as the time elapsed since it entered it. Analyzing this diagnostic timescale provides valuable information for optimally sizing and ... [more ▼]

The age of a water particle in a shallow man-made reservoir is defined as the time elapsed since it entered it. Analyzing this diagnostic timescale provides valuable information for optimally sizing and operating such structures. Here, the constituent-oriented age and residence time theory (CART) is used to obtain not only the mean age, but also the water age distribution function at each location. The method is applied to 10 different shallow reservoirs of simple geometry (rectangular), in a steady-state framework. The results show that complex, multimodal water age distributions are found, implying that focusing solely on simple statistics (e.g., mean or median age) fails to reflect the complexity of the actual distribution of water age. The latter relates to the fast or slow pathways that water particles may take for traveling from the inlet to the outlet of the reservoirs. [less ▲]

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See detailInfluence of model formulation on the critical morphological acceleration factor: an analytical study
Dewals, Benjamin ULiege; Archambeau, Pierre ULiege; Pirotton, Michel ULiege et al

E-print/Working paper (2020)

The morphological acceleration factor (Morfac) has been used for over two decades to speed-up long term morphodynamic simulations. However, the Morfac values are usually set heuristically and hardly any ... [more ▼]

The morphological acceleration factor (Morfac) has been used for over two decades to speed-up long term morphodynamic simulations. However, the Morfac values are usually set heuristically and hardly any study investigated theoretically the critical Morfac value leading to a predefined level of accuracy. In this research, we evaluated theoretically the critical Morfac value from the analysis of the amplitude and phase errors induced by the use of Morfac. While the few existing studies focused only on relatively low Froude numbers and a single mathematical formulation of the morphodynamic model, we consider here a significantly wider range of Froude numbers, including supercritical flow, and we compare four different model formulations. We show that the model formulation leading to the highest critical Morfac values for subcritical flow is not the same as for supercritical flow. [less ▲]

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See detailA combined experimental and numerical strategy to assess the influence of model geometric distortion in laboratory scale modelling of urban flooding
Li, Xuefang ULiege; Erpicum, Sébastien ULiege; Mignot, Emmanuel et al

Conference (2020, July)

Accurate modelling of urban flood hazard remains hampered by a lack of suitable validation data. In contrast with water marks and inundation extent, discharge partition in-between streets and flow fields ... [more ▼]

Accurate modelling of urban flood hazard remains hampered by a lack of suitable validation data. In contrast with water marks and inundation extent, discharge partition in-between streets and flow fields are generally unknown, while they have a strong influence on flood risk (human destabilization, scour, contaminant transport). Laboratory experiments may provide a valuable complement to field data to achieve robust validation of flood hazard models. However, urban flooding is a multiscale phenomenon, with horizontal length scales (~ 103 m) are considerably larger than the vertical ones (~ 1 m). Therefore, recent experimental studies of urban flooding used geometrically distorted scale models, with a vertical scale factor smaller than the horizontal one. Though, little is known so far on the bias induced by model geometric distortion in the case of urban flooding. To address this issue, we have combined computational modelling with laboratory experiments. Based on 100+ numerical simulations, the bias induced by model geometric distortion on flow depth and discharge partition was found of the order of 10 %, which is not negligible compared to other uncertainties involved in urban flood hazard modelling. Moreover, when the geometric distortion is varied, the induced bias shows an intriguing non-monotonous evolution, which we could relate to a competition between frictional and secondary head losses. New tailored laboratory experiments are on-going on a “series” of laboratory scale models, i.e. several laboratory models representing the same urban layout at various scales. The outcomes of these experiments will make more robust the conclusions drawn from computational modelling. [less ▲]

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See detailNumerical insights into the effects of model geometric distortion in laboratory experiments of urban flooding
Li, Xuefang ULiege; Erpicum, Sébastien ULiege; Mignot, Emmanuel et al

in Water Resources Research (2020)

Geometrically distorted scale models have been a valuable tool for physical modelling of urban flooding in a network of streets. However, little is known so far about the bias induced in such cases by the ... [more ▼]

Geometrically distorted scale models have been a valuable tool for physical modelling of urban flooding in a network of streets. However, little is known so far about the bias induced in such cases by the model geometric distortion. Here, we use 2D computational modelling to provide a first systematic quantification of this bias in the case of a synthetic urban layout. The bias is found to be generally small, with the maximum deviations of the upscaled flow depth and discharge partition from the corresponding values of the undistorted model being around 10 % in the case of relatively rapid and shallow flow conditions. When the geometric distortion is increased, the computations reveal a non-monotonous pattern of the flow variables (depth, discharge partition, size of flow separation zones), which results from a competition between declining frictional losses and growing local losses in the model. These findings may guide the design of distorted scale models of urban flooding and assist the interpretation of laboratory observations for assessing flood protection measures, for process understanding or for validating computational modelling. [less ▲]

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