References of "Dewals, Benjamin"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailOvertopping induced failure of non-cohesive, homogenous fluvial dikes
Rifai, Ismail ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Water Resources Research (in press)

Accurate predictions of breach characteristics are necessary to reliably estimate the outflow hydrograph and the resulting inundation close to fluvial dikes. Laboratory experiments on the breaching of ... [more ▼]

Accurate predictions of breach characteristics are necessary to reliably estimate the outflow hydrograph and the resulting inundation close to fluvial dikes. Laboratory experiments on the breaching of sand-filled fluvial dikes were performed, considering a flow parallel to the dike axis. The breach was triggered by overtopping of the dike crest. A detailed monitoring of the transient evolution of the breach geometry was conducted, providing key insights into the gradual and complex processes involved in fluvial dike failure. The breach develops in two phases: (1) the breach becomes gradually wider and deeper eroding on the downstream side along the main channel, and (2) breach widening controlled by side slope failures, continuing in the downstream direction only. Increasing the inflow discharge in the main channel, the breach formation time decreases significantly and the erosion occurs preferentially on the downstream side. The downstream boundary condition has a strong influence on the breach geometry and the resulting outflow hydrograph. [less ▲]

Detailed reference viewed: 17 (3 ULg)
Full Text
Peer Reviewed
See detailMaximum energy dissipation to explain velocity fields in shallow reservoirs
Westhoff, Martijn; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Journal of Hydraulic Research (in press)

Shallow reservoirs are often used as sediment traps or storage basins, in which sedimentation depends on the flow pattern: Short rectangular reservoirs reveal a straight jet from inlet to outlet with on ... [more ▼]

Shallow reservoirs are often used as sediment traps or storage basins, in which sedimentation depends on the flow pattern: Short rectangular reservoirs reveal a straight jet from inlet to outlet with on both sides identical recirculation zones. In longer reservoirs, the main jet reattaches to the side of the reservoir leading to a small and a large recirculation zone. Previous studies found an empirical geometric relation describing the switch between these two flow patterns. In this study, we demonstrate, with a simple analytical model, that this switch coincides with a maximization of energy dissipation in the shear layer between the main jet and recirculation zones: Short reservoirs dissipate more energy when the flow pattern is symmetric, while longer reservoirs dissipate more energy with an asymmetric pattern. This approach enables to predict the flow patterns without detailed knowledge of small scale processes, potentially useful in the early phase of reservoir design. [less ▲]

Detailed reference viewed: 38 (6 ULg)
Full Text
Peer Reviewed
See detailInfluence of urban patterns on flooding
Bruwier, Martin ULg; Mustafa, Ahmed; Aliaga, Daniel et al

in E-proceedings of the 37th IAHR World Congress (2017, August)

The goal of this paper is to identify the respective influence of different characteristics of urban patterns on urban flooding. A set of 2,290 alternate urban patterns was generated randomly using an ... [more ▼]

The goal of this paper is to identify the respective influence of different characteristics of urban patterns on urban flooding. A set of 2,290 alternate urban patterns was generated randomly using an urban generator tool providing the geometry of buildings and their relative location to the ground, over a square area of 1 km². Steady 2-D hydraulic computations were performed for these 2,290 different urban patterns with identical hydraulic boundary conditions. The computational time was reduced by using an anisotropic porosity model. This model uses relatively coarse computational cells; but preserves information from the detailed topographic data through the use of porosity parameters. Based on the computed maps of waterdepths for the 2,290 urban patterns, a sensitivity analysis based on a multiple linear regression was performed to outline the most influential urban characteristics. [less ▲]

Detailed reference viewed: 37 (9 ULg)
Full Text
See detailShallow water model with anisotropic porosity for flood modelling on Cartesian grids
Bruwier, Martin ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

Conference (2017, June)

Detailed topographic data have become widely available for inundation mapping. While the use of such high-resolution data enables the computation of flow variables at a fine scale, the computation time ... [more ▼]

Detailed topographic data have become widely available for inundation mapping. While the use of such high-resolution data enables the computation of flow variables at a fine scale, the computation time remains too high for many practical applications. In contrast, models solving the shallow-water equations with porosity provide a useful tool to improve the computational efficiency, while preserving to some extent the detailed topographic information through porosity parameters. In this study, we present a new model solving the fully dynamic shallow water equations with anisotropic porosity based on Cartesian grids. Using a Cartesian grid leads to specific challenges, particularly as regards the definition of the conveyance porosities at the cell edges. Moreover, the presented model is further improved by a merging method so as to increase the computational efficiency without affecting the overall accuracy. The performance of the model has been evaluated based on a wide range of test cases, which confirm the validity of the model and the benefits of such a modelling framework. [less ▲]

Detailed reference viewed: 34 (8 ULg)
Full Text
See detailSystematic flood modelling to support flood-proof urban design
Bruwier, Martin ULg; Mustafa, Ahmed; Aliaga, Daniel et al

Conference (2017, April)

Urban flood risk is influenced by many factors such as hydro-meteorological drivers, existing drainage systems as well as vulnerability of population and assets. The urban fabric itself has also a complex ... [more ▼]

Urban flood risk is influenced by many factors such as hydro-meteorological drivers, existing drainage systems as well as vulnerability of population and assets. The urban fabric itself has also a complex influence on inundation flows. In this research, we performed a systematic analysis on how various characteristics of urban patterns control inundation flow within the urban area and upstream of it. An urban generator tool was used to generate over 2,250 synthetic urban networks of 1 km². This tool is based on the procedural modelling presented by Parish and Müller (2001) which was adapted to generate a broader variety of urban networks. Nine input parameters were used to control the urban geometry. Three of them define the average length, orientation and curvature of the streets. Two orthogonal major roads, for which the width constitutes the fourth input parameter, work as constraints to generate the urban network. The width of secondary streets is given by the fifth input parameter. Each parcel generated by the street network based on a parcel mean area parameter can be either a park or a building parcel depending on the park ratio parameter. Three setback parameters constraint the exact location of the building whithin a building parcel. For each of synthetic urban network, detailed two-dimensional inundation maps were computed with a hydraulic model. The computational efficiency was enhanced by means of a porosity model. This enables the use of a coarser computational grid , while preserving information on the detailed geometry of the urban network (Sanders et al. 2008). These porosity parameters reflect not only the void fraction, which influences the storage capacity of the urban area, but also the influence of buildings on flow conveyance (dynamic effects). A sensitivity analysis was performed based on the inundation maps to highlight the respective impact of each input parameter characteristizing the urban networks. The findings of the study pinpoint which properties of urban networks have a major influence on urban inundation flow, enabling better informed flood-proof urban design. [less ▲]

Detailed reference viewed: 38 (5 ULg)
Full Text
Peer Reviewed
See detailOn the transition between symmetric and asymmetric flow in rectangular shallow reservoirs - a case of maximum energy dissipation?
Westhoff, Martijn; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in 4th International Symposium of Shallow Flows (2017)

Shallow reservoirs are often used as sediment traps or storage basins, in which sedimentation depends on the flow pattern. Short rectangular reservoirs reveal a straight jet from inlet to outlet with ... [more ▼]

Shallow reservoirs are often used as sediment traps or storage basins, in which sedimentation depends on the flow pattern. Short rectangular reservoirs reveal a straight jet from inlet to outlet with identical recirculation zones on both sides. In longer reservoirs, the main jet reattaches to the side of the reservoir leading to small and large recirculation zones. Previous studies have found an empirical geometric relation describing the switch between these two flow patterns. In this study, we demonstrate, with a simple analytical model, that this switch coincides with a maximization of energy dissipation in the shear layer between the main jet and recirculation zones: Short reservoirs dissipate more energy when the flow pattern is symmetric, while longer reservoirs dissipate more energy with an asymmetric pattern. This approach enables the prediction of the flow patterns without detailed knowledge of small scale processes, potentially useful in the early phase of reservoir design. [less ▲]

Detailed reference viewed: 15 (0 ULg)
Full Text
Peer Reviewed
See detailLooking beyond general metrics for model comparison – lessons from an international model intercomparison study
de Boer-Euser, Tanja; Bouaziz, Laurène; De Niel, Jan et al

in Hydrology and Earth System Sciences (2017), 21

International collaboration between research institutes and universities is a promising way to reach consensus on hydrological model development. Although comparative studies are very valuable for ... [more ▼]

International collaboration between research institutes and universities is a promising way to reach consensus on hydrological model development. Although comparative studies are very valuable for international cooperation, they do often not lead to very clear new insights regarding the relevance of the modelled processes. We hypothesise that this is partly caused by model complexity and the comparison methods used, which focus too much on a good overall performance instead of focusing on specific events. In this study, we use an approach that focuses on the evaluation of specific events and characteristics. Eight international research groups calibrated their hourly model on the Ourthe catchment in Belgium and carried out a validation in time for the Ourthe catchment and a validation in space for nested and neighbouring catchments. The same protocol was followed for each model and an ensemble of best performing parameter sets was selected. Although the models showed similar performances based on general metrics (i.e. Nash–Sutcliffe Efficiency), clear differences could be observed for specific events. The results illustrate the relevance of including a very quick flow reservoir preceding the root zone storage to model peaks during low flows and including a slow reservoir in parallel with the fast reservoir to model the recession for the Ourthe catchment. This intercomparison enhanced the understanding of the hydrological functioning of the catchment and, above all, helped to evaluate each model against a set of alternative models. [less ▲]

Detailed reference viewed: 30 (1 ULg)
Full Text
Peer Reviewed
See detailCould Piano key weirs be subject to nappe oscillations?
Lodomez, Maurine ULg; Pirotton, Michel ULg; Dewals, Benjamin ULg et al

in 3rd International Workshop on Labyrinth and Piano Key Weirs - PKW 2017 (2017)

Nappe oscillation may affect a variety of free overflow hydraulic structures operating at low heads such as crest gates and various types of weirs. This phenomenon produces oscillations in the thin nappe ... [more ▼]

Nappe oscillation may affect a variety of free overflow hydraulic structures operating at low heads such as crest gates and various types of weirs. This phenomenon produces oscillations in the thin nappe cascading downstream of the control structure. These oscillations can result in a high noise levels that may affect people and structures located nearby. With long linear and thin overtopping walls, piano key weirs might be subject to strong nappe oscillation risks, as a few documented cases with labyrinth weirs. However, the specific geometric features of piano key weirs, such as the outlet ramps or the limited width of the inlet apex, could perhaps prevent the development of nappe oscillation. In this paper, a prototype-scale linear weir is operated to assess the risk of nappe oscillations on a piano key weir like configuration (sidewall). In particular, the effect of the weir width and inclined apron is analyzed. The experimental results show that nappe oscillation development should not occur on piano key weir, contrary to what might be observed on a labyrinth weir with the same crest. [less ▲]

Detailed reference viewed: 24 (5 ULg)
Full Text
Peer Reviewed
See detailEvaluation et gestion des scenarii de dysfonctionnement des barrages-réservoirs en Belgique
Liégeois, Benoît; Pirotton, Michel ULg; Dewals, Benjamin ULg et al

in Sûreté des barrages et enjeux (2016, November)

Belgium has fifteen structures included in the list of large dams of the International Committee on Large Dams. Six are managed by Engie Company, the other nine are owned by the Walloon regional public ... [more ▼]

Belgium has fifteen structures included in the list of large dams of the International Committee on Large Dams. Six are managed by Engie Company, the other nine are owned by the Walloon regional public authority. The Belgian legislator has never enacted specific rules for large dams. However, managers have always been concerned with this issue. They developed procedures and methods that were subject to exchanges of experience with their counterparts, in particular through the Belgian Committee on Large Dams. In this ongoing research of security, the impact of multiple failure scenarios (dam break, quick emptying …) on the people and the environment downstream of dams is a particular focal point. An impact study has been conducted for the main plants. This study is based on a deterministic numerical method. The methodology, the assumptions regarding the failure mode or emptying and the lessons learned from the analyses are presented. These results are an important step in the assessment and the management of risks. Indeed, regulations were recently enacted for the management and the coordination of any activity likely to seriously impact public safety during crisis periods. These rules apply therefore for large dams. In this context, managers have established an emergency plan for each structure. This paper provides a broad overview on the issues of the evaluation and the management of dysfunction risks of Belgian dams, as well as on approaches and collaborations initiated between the private managers and public authority. [less ▲]

Detailed reference viewed: 22 (1 ULg)
Full Text
See detailA benchmark for urban flood modelling
Arrault, Anaïs; Finaud-Guyot, Pascal; Archambeau, Pierre ULg et al

Poster (2016, October 25)

Detailed reference viewed: 19 (2 ULg)
Full Text
See detail1-D shallow water model for industrial practice: Application to the River Romanche
Goffin, Louis ULg; Dewals, Benjamin ULg; Erpicum, Sébastien ULg et al

Scientific conference (2016, October 25)

Detailed reference viewed: 36 (2 ULg)
Full Text
Peer Reviewed
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)

Detailed reference viewed: 60 (15 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 52 (7 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 85 (15 ULg)