References of "Dewals, Benjamin"
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See detailContinuous monitoring of fluvial dike breaching by a Laser Profilometry Technique
Rifai, Ismail; Schmitz, Vincent ULiege; Erpicum, Sébastien ULiege et al

in Water Resources Research (in press), 56

A non-intrusive, high resolution Laser Profilometry Technique (LPT) has been developed for continuous monitoring of the three dimensional (3D) evolving breach in laboratory models of non-cohesive fluvial ... [more ▼]

A non-intrusive, high resolution Laser Profilometry Technique (LPT) has been developed for continuous monitoring of the three dimensional (3D) evolving breach in laboratory models of non-cohesive fluvial dikes. This simple and low cost setup consists of a commercial digital video camera and a sweeping red diode 30 mW laser projecting a sheet over the dike. The 2D image coordinates of each deformed laser profile incident on the dike are transformed into 3D object coordinates using the Direct Linear Transformation algorithm. All 3D object coordinates computed over a laser sweeping cycle are merged to generate a cloud of points describing the instantaneous surface. The DLT-based image processing algorithm uses control points and reference axes, so that no prior knowledge is needed on the position, orientation and intrinsic characteristics of the camera, nor on the laser position. Because the dike is partially submerged, ad hoc refraction correction has been developed. Algorithms and instructions for the implementation of the LPT are provided. Reconstructions of a dike geometry with the LPT and with a commercial laser scanner are compared in dry conditions. Using rigid dike geometries, the repeatability of the measurements, the refraction correction, and the dike reconstruction have been evaluated for submerged conditions. Two laboratory studies of evolving fluvial dike breaching due to flow overtopping have been conducted to demonstrate the LPT capabilities and accuracy. The LPT has advantages in terms of flexibility and spatiotemporal resolution, but high turbidity and water surface waves may lead to inaccurate geometry reconstructions. [less ▲]

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See detailThe need to integrate flood and drought disaster risk reduction strategies
Ward, Philip; de Ruiter, Marleen; Mård, Johanna et al

in Journal of Water Security (in press)

Most research on hydrological risks focuses either on flood risk or drought risk, whilst floods and droughts are two extremes of the same hydrological cycle. To better design disaster risk reduction (DRR ... [more ▼]

Most research on hydrological risks focuses either on flood risk or drought risk, whilst floods and droughts are two extremes of the same hydrological cycle. To better design disaster risk reduction (DRR) measures and strategies, it is important to consider interactions between these closely linked phenomena. We show examples of: how flood or drought DRR measures can have (unintentional) positive or negative impacts on risk of the opposite hazard; and (b) how flood or drought DRR measures can be negatively impacted by the opposite hazard. We focus on dikes and levees, dams, stormwater control and upstream measures, subsurface storage, migration, agricultural practices, and vulnerability and preparedness. We identify key challenges for moving towards a more holistic risk management approach. [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 (in press)

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 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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See detailProcedural generation of flood-sensitive urban layouts
Mustafa, Ahmed Mohamed El Saeid ULiege; Zhang, Xiao Wei; Aliaga et al

in Environment and Planning B: Urban Analytics and City Science (2020), 47(5), 889-911

Aside from modeling geometric shape, three-dimensional (3D) urban procedural modeling has shown its value in understanding, predicting and/or controlling effects of shape on design and urban planning. In ... [more ▼]

Aside from modeling geometric shape, three-dimensional (3D) urban procedural modeling has shown its value in understanding, predicting and/or controlling effects of shape on design and urban planning. In this paper, instead of the construction of flood resistant measures, we create a procedural generation system for designing urban layouts that passively reduce water depth during a flooding scenario. Our tool enables exploring designs that passively lower flood depth everywhere or mostly in chosen key areas. Our approach tightly integrates a hydraulic model and a parameterized urban generation system with an optimization engine so as to find the least cost modification to an initial urban layout design. Further, due to the computational cost of a fluid simulation, we train neural networks to assist with accelerating the design process. We have applied our system to several real-world locations and have obtained improved 3D urban models in just a few seconds. [less ▲]

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See detailDiscussion of "modeling and Prototype Testing of Flows over Flip-Bucket Aerators" by Penghua Teng and James Yang
Erpicum, Sébastien ULiege; Dewals, Benjamin ULiege; Archambeau, Pierre ULiege et al

in Journal of Hydraulic Engineering (2020), 146(5),

The Authors propose an interesting comparison between physical scale modeling, CFD modeling and field observations related to a unique spillway with flip buckets and built-in aerators. Despite the field ... [more ▼]

The Authors propose an interesting comparison between physical scale modeling, CFD modeling and field observations related to a unique spillway with flip buckets and built-in aerators. Despite the field observations are mainly qualitative, the Discussers would like to thank the Authors for sharing with the scientific community these results. Indeed, such analysis are very valuable but are too rare. Physical models and CFD are both modeling tools. They both suffer limitations and, consequently, their results need to be carefully and objectively discussed and validated. Comparison to quantitative prototype data is the only way to proof the validity of a modeling technique for real projects. However, such validation data remain sparse and rare, in particular considering large hydraulic structures. In the following, the Discussers aim to raise one issue in the Authors’ research and to highlight recent contributions and existing datasets, which are of direct relevance for the interpretation and discussion of the Authors’ results. [less ▲]

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See detailInfluence of urban forms on surface flow in urban pluvial flooding
Bruwier, Martin ULiege; Maravat, Claire; Mustafa, Ahmed et al

in Journal of Hydrology (2020), 582

This paper presents a systematic analysis of the influence of nine urban characteristics (distance be-tween buildings, mean building size, building coverage, etc.) on surface flow in case of pluvial ... [more ▼]

This paper presents a systematic analysis of the influence of nine urban characteristics (distance be-tween buildings, mean building size, building coverage, etc.) on surface flow in case of pluvial flooding. Time dependent stored volumes, outflow discharges and mean water depths were comput-ed for a set of 2,000 synthetic urban forms, considering various terrain slopes and return periods of the rainfall. An efficient porosity-based surface flow model was used to compute the 2D flow varia-bles. Statistical analysis of the relationship between the flow and urban variables highlights that the flooding severity is mostly influenced by the building coverage. [less ▲]

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See detailDiscrepancies in flood modelling approaches in transboundary river systems: legacy of the past or well-grounded choices?
Kitsikoudis, Vasileios ULiege; Becker, Bernhard; Huismans, Ymkje et al

in Water Resources Management (2020), 34

Flood modelling in transnational rivers requires efficient cross-border collaboration among the riparian countries. Currently, each country/region usually uses a different hydraulic modelling approach ... [more ▼]

Flood modelling in transnational rivers requires efficient cross-border collaboration among the riparian countries. Currently, each country/region usually uses a different hydraulic modelling approach, which may hinder the modelling of the entire river. For the sake of accurate and consistent river modelling there is a necessity for the establishment of a framework that fosters international collaborations. This study investigates the current hydraulic modelling approach across the whole length of the River Meuse, the main course of which crosses three North-western European countries. The numerical models used by French, Belgian, and Dutch agencies and authorities were interconnected by exchanging boundary conditions at the borders. At the central part of the river, the Belgian hydraulic model assumed steady flow conditions, while the rest of the river was modelled in unsteady mode. Results for various flood scenarios revealed a distinctive pattern of water depths at the Belgian-Dutch border. To clarify whether this is a bias induced by the change in modelling approach at the border (steady vs. unsteady), we remodelled a stretch of the river across the Belgian-Dutch border using a consistent unsteady modelling approach. The steady and unsteady approaches led to similar patterns across the border, hence discarding the hypothesis of a bias resulting from a change in the employed model. Instead, the pattern in water depths was attributed to a change in the topography of the Meuse Valley, where there is a transition from a narrow steep corridor with limited water storing capacity in Ardennes massif to wide floodplains in the Dutch lowlands. The associated flood damping for the 100-year discharge is less than 1 % in the Ardennes and exceeds 15 % in the Dutch lowlands. It can be inferred that the current differences in regional hydraulic modelling approaches for the River Meuse are generally well-grounded and not just a legacy of the past. [less ▲]

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See detailBreaching of fluvial dykes: influence of the dyke geometry
Schmitz, Vincent ULiege; Erpicum, Sébastien ULiege; Rifai, Ismail et al

in Proceedings of 10th Conference on Fluvial Hydraulics River Flow 2020 (2020)

Failure of fluvial dykes often leads to devastating consequences in the protected areas. Various factors can trigger breaching; but overtopping flow is, by far, the most frequent cause of failure of ... [more ▼]

Failure of fluvial dykes often leads to devastating consequences in the protected areas. Various factors can trigger breaching; but overtopping flow is, by far, the most frequent cause of failure of fluvial dykes. Nevertheless, the breaching mechanisms are still not well understood, and their prediction remains challenging. Most experimental studies so far focused on overtopping of dykes perpendicular to the main flow, while few analyzed fluvial dykes, i.e., dykes parallel to the main flow. Recently, Rifai et al. (2017, 2018) performed 54 laboratory tests of fluvial dyke failure to assess the influence of the channel inflow discharge, the downstream boundary condition, the floodplain tailwater, the channel size as well as the bottom and dyke material. In contrast, the influence of the dyke geometry was never investigated systematically for the case of fluvial dykes. Here, we present 40 new laboratory tests carried out to highlight the influence of the dyke upstream and downstream slopes as well as the crest width on the breaching process of fluvial dykes. Results show that the combined effect of these three geometrical parameters can be lumped into a single non-dimensional parameter, as introduced by Müller et al. (2016) for the frontal configuration. Also, the influence of the dyke geometry remains limited compared to that of the other governing parameters, such as the inflow discharge in the main channel. These findings make a valuable step towards a better understanding of the breaching dynamics of fluvial dykes. [less ▲]

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See detailInfluence of model geometric distortion in laboratory scale modelling of urban flooding
Li, Xuefang ULiege; Erpicum, Sébastien ULiege; Pirotton, Michel ULiege et al

in Proceedings of 10th Conference on Fluvial Hydraulics River Flow 2020 (2020)

Urban flooding at the block- or district-level is characterized by comparatively larger horizontal length scales than vertical ones. Therefore, a number of laboratory experi-ments of urban flooding were ... [more ▼]

Urban flooding at the block- or district-level is characterized by comparatively larger horizontal length scales than vertical ones. Therefore, a number of laboratory experi-ments of urban flooding were based on geometrically distorted scale models. Here, we investigate the influence of model geometric distortion on the flow processes in two simple settings representative of urban flooding: a single prismatic street and a street junction. We specifically compare the upstream flow depths predicted from laboratory observations using different geometric distortions. The predicted upstream flow depths consistently decrease as the model geometric distortion is increased. The bias induced by model geometric distortion, estimated as the relative difference between predictions from distorted and undistorted models is of order of 15% and 7% for the prismatic street and the street junction, respectively. This difference may be attributed to a difference in the relative importance of frictional losses and local head losses in the two settings. The outcomes of the study provide valuable guidance for the design of laboratory models of urban flooding. [less ▲]

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See detailUnderground Pumped-Storage Hydropower (UPSH) at the Martelange Mine (Belgium): Underground Reservoir Hydraulics
Kitsikoudis, Vasileios ULiege; Archambeau, Pierre ULiege; Dewals, Benjamin ULiege et al

in Energies (2020), 13(14), 3512

The intermittent nature of most renewable energy sources requires their coupling with an energy storage system, with pumped storage hydropower (PSH) being one popular option. However, PSH cannot always be ... [more ▼]

The intermittent nature of most renewable energy sources requires their coupling with an energy storage system, with pumped storage hydropower (PSH) being one popular option. However, PSH cannot always be constructed due to topographic, environmental, and societal constraints, among others. Underground pumped storage hydropower (UPSH) has recently gained popularity as a viable alternative and may utilize abandoned mines for the construction of the lower reservoir in the underground. Such underground mines may have complex geometries and the injection/pumping of large volumes of water with high discharge could lead to uneven water level distribution over the underground reservoir subparts. This can temporarily influence the head difference between the upper and lower reservoirs of the UPSH, thus affecting the efficiency of the plant or inducing structural stability problems. The present study considers an abandoned slate mine in Martelange in Southeast Belgium as the lower, underground, reservoir of an UPSH plant and analyzes its hydraulic behavior. The abandoned slate mine consists of nine large chambers with a total volume of about 550,000 m3, whereas the maximum pumping and turbining discharges are 22.2 m3/s. The chambers have different size and they are interconnected with small galleries with limited discharge capacity that may hinder the flow exchange between adjacent chambers. The objective of this study is to quantify the effect of the connecting galleries cross-section and the chambers adequate aeration on the water level variations in the underground reservoir, considering a possible operation scenario build upon current electricity prices and using an original hydraulic modelling approach. The results highlight the importance of adequate ventilation of the chambers in order to reach the same equilibrium water level across all communicating chambers. For fully aerated chambers, the connecting galleries should have a total cross-sectional area of at least 15 m2 to allow water flow through them without significant restrictions and maintain similar water level at all times. Partially aerated chambers do not attain the same water level because of the entrapped air; however, the maximum water level differences between adjacent chambers remain relatively invariant when the total cross-sectional area of the connecting galleries is greater than 8 m2. The variation of hydraulic roughness of the connecting galleries affects the water exchange through small connecting galleries but is not very influential on water moving through galleries with large cross-sections. [less ▲]

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See detailNappe oscillations on free-overfall structures, data from laboratory experiments
Lodomez, Maurine ULiege; Tullis, Blake; Archambeau, Pierre ULiege et al

in Scientific Data (2020), 7(1), 180

This paper presents a dataset obtained from fifty-two laboratory experiments of nappe oscillations on free overfall structures. Data were collected on two complementary experimental setups, each ... [more ▼]

This paper presents a dataset obtained from fifty-two laboratory experiments of nappe oscillations on free overfall structures. Data were collected on two complementary experimental setups, each consisting of a linear weir model. The dataset covers test configurations involving varied geometric parameters (i.e. weir crest shape, weir width, fall height and nappe confinement) and inflow discharges. The following experimental data were produced: assessment of nappe oscillation occurrence and associated frequencies. The later measurements were performed using characterization techniques (image and sound analysis) developed for this research. Reuse of the collected data will support efforts to improve the understanding of the physical processes underpinning nappe oscillation and to validate numerical modelling of the phenomenon. [less ▲]

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See detailInteractions between numerical and physical modelling for the design and optimization of hydraulic structures - Example of a large hydroelectric complex
Erpicum, Sébastien ULiege; Archambeau, Pierre ULiege; Dewals, Benjamin ULiege et al

in Proceedings of the International Symposium on Hydraulic Structures, XXII Congreso Latinoamericano de Hidráhulica (2020)

This paper describes the successful combination of both physical and numerical modelling techniques applied to the scale model study of a large hydroelectric complex in India. Thanks to accurate numerical ... [more ▼]

This paper describes the successful combination of both physical and numerical modelling techniques applied to the scale model study of a large hydroelectric complex in India. Thanks to accurate numerical simulations, the physical model layout and the time to studies have been drastically reduced. First, prior to the design of the scale model, a global numerical simulation of the dam reservoir has been carried out, on the basis of the entire set of available topographic data. The simulation results supply the flow conditions in the upstream reservoir, particularly in the vicinity of the dam and the spillway crest. Subsequently, a second numerical computation has been performed to simulate the flow in a scale model representing only a small part of the reservoir upstream of the dam. The suitable correspondence between flow conditions in both cases has been demonstrated. This two-steps approach has enabled a significant reduction in the size of the scale model, and hence, a lower cost as well as a shorter delay for building the model. Simultaneously, it has been possible to decrease the scale factor at constant cost. In conclusion, the present paper provides convincing evidence that the increase in computers performance and the efficiency of contemporary free-surface flow solvers lead to useful numerical information for the optimal design and exploitation of scale models. [less ▲]

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See detailWarning waves to protect human beings in bypassed river reaches of hydropower schemes
Dewals, Benjamin ULiege; Stilmant, Frédéric; Erpicum, Sébastien ULiege et al

in Proceedings of 10th Conference on Fluvial Hydraulics River Flow 2020 (2020)

River reaches located downstream of a hydropower plant are conductive to sudden variations in flow discharge. Warning waves constitute a useful non-structural measure to warn users of the downstream river ... [more ▼]

River reaches located downstream of a hydropower plant are conductive to sudden variations in flow discharge. Warning waves constitute a useful non-structural measure to warn users of the downstream river reaches of an imminent increase in discharge. However, determining the up-stream release hydrograph to generate a suitable warning wave is an inverse problem, intricate to solve. We present here a two-model strategy, in which a kinematic analytical model provides valuable insights to guide the solution of a 2D computational model. [less ▲]

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See detailAddition of fine material is expected to strengthen fluvial dikes ... does it really?
Dewals, Benjamin ULiege; Rifai, Ismail; El kadi Abderrezzak, Kamal et al

Conference (2020)

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See detailNappe flows on a prototype-scale stepped chute: observations of flow patterns, air-water flow properties, energy dissipation and dissolved oxygen
Felder, Stefan; Geuzaine, Margaux ULiege; Dewals, Benjamin ULiege et al

in Journal of Hydro-Environment Research (2019), 27

Air-water flows occur commonly in stepped spillways including the nappe flow regime for low flow rates. The present laboratory experiments researched the nappe flow regime in a stepped chute with ... [more ▼]

Air-water flows occur commonly in stepped spillways including the nappe flow regime for low flow rates. The present laboratory experiments researched the nappe flow regime in a stepped chute with prototype-scale steps height providing unique insights into the evolution of nappe flows along a stepped chute. Detailed visual observations highlighted the varying flow features along the stepped chute including the evolution of flow aeration, of jet properties and of instationarities in form of jump waves and cavity fluctuations with typical frequencies of around 1 Hz. These instationarities were caused by complex flow interactions at the impingement of the jet on the horizontal step face. Detailed air-water flow measurements revealed the complexity of the flows highlighting both S-shape and jet-like void fraction distributions and jet-like interfacial velocity distributions downstream of the jet impact and at step edges. This resulted in a downwards shift of the bubble count rate distributions closer to the step face. The nappe flows showed strong energy dissipation and reaeration performances along the stepped chute. The present study provided a robust and extensive characterisation of nappe flows and due to the large scale of the experiments, the results should provide confidence for the design of stepped chutes with embankment dam slope. [less ▲]

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See detailA multi-level, multi-scenario perspective on the interplay between urban planning and flood risk management
Dewals, Benjamin ULiege; Bruwier, Martin ULiege; Mustafa, Ahmed et al

Conference (2019, September 19)

Worldwide, urban planning has a prevailing influence on the evolution of flood risk. At the municipal and regional levels, bans (or restrictions) on new developments in flood-prone areas enable mitigating ... [more ▼]

Worldwide, urban planning has a prevailing influence on the evolution of flood risk. At the municipal and regional levels, bans (or restrictions) on new developments in flood-prone areas enable mitigating increases in vulnerability. At the local level, flood-sensitive urban design contributes to lowering the residual risk, by acting on both the hazard and the vulnerability. The risk-reduction potential of various urban planning policies may strongly depend on the type of flooding (e.g. riverine vs. pluvial). In recent research, we shed light on the effects of contrasting urban planning policies at the regional and local levels, considering both riverine and pluvial floods. First, at the regional level, we looked at the effect of “sustainable urban planning” compared to a “business-as-usual” approach for the case of riverine floods. While the latter is characterized by substantial urban sprawl, the former tends to promote more compact developments, such as densification of already-urbanized areas. We used a combination of agent-based and cellular automata models to simulate urbanization and densification over the next decades in the southern part of Belgium [1]. For this case study, all scenarios based on “sustainable urban planning” lead to values of future flood risk comparatively higher than in the “business-as-usual” scenarios. This results from the concentration of existing urbanized areas in the lower part of the valleys, given the historical appeal of the rivers for economic activities and transportation. At the local level, we used procedural modelling to compare thousands of different layouts of buildings in terms of their influence on flood hazard. Focusing on the case of riverine floods typical of lowland rivers (mild slope, relatively long flood waves), we found that maximizing connectivity throughout the urbanized area enables mitigating to some extent the detrimental effects of developments on the upstream areas [2]. Again, this contrasts with overarching principles of sustainable urban planning, which recommend avoiding voids in-between buildings, hence hampering flow connectivity. The analysis was recently extended to pluvial flooding, for which the conclusions drawn for riverine floods are not directly transferable. Overall, these results suggest that sustainable urban planning is certainly the way to go; but some of the underlying principles need to be modulated when it comes to developments in flood-prone areas. This emphasizes the strongly interdisciplinary nature of sustainable urban design and of building resilience into urban systems. While the results so far were harvested by coupling advanced computational approaches in urbanization modelling and inundation modelling, a next stage in the research will consist in observation-based verification of the findings. References [1] Mustafa, A. et al. (2018). Effects of spatial planning on future flood risks in urban environments. J. Environ. Manage. 225, 193–204. [2] Bruwier, M. et al. (2018). Influence of urban pattern on inundation flow in floodplains of lowland rivers. Sci. Total Environ. 622-623, 446–458. [less ▲]

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