Projet interreg IVb - Rapport d'activité intermédiaire pour le comité d'accompagnement

Report (2010)

Flood risk analysis in Wallonia: micro (and meso-)scale approaches

Conference (2010, October 25)

Flood risk analysis has been undertaken in Wallonia in the framework of several national and international research projects. The analysis relies on a micro-scale procedure, which involves • hazard ... [more ▼]

Flood risk analysis has been undertaken in Wallonia in the framework of several national and international research projects. The analysis relies on a micro-scale procedure, which involves • hazard modelling by means of detailed 2D inundation modelling • as well as processing of high resolution topographic and land use database for vulnerability modelling. The inundation modelling is conducted using the fully dynamic flow model WOLF 2D, entirely developed at the University of Liege. The model is run on a highly accurate DEM resulting from the combination of laser altimetry and, when available, sonar bathymetry. The typical grid spacing for the simulations is kept as low as 2m, which is definitely fine enough to represent the complex flows occurring at the scale of individual buildings and streets in urbanized floodplains. In this way, both the static and dynamic impacts of the flow may be characterized for all affected assets. This approach has been extensively applied since 2003 to issue inundation maps throughout the Walloon region based on detailed 2D flow modelling. Consequently, the outcomes of such detailed inundation modelling constitute suitable inputs for the subsequent exposure analysis, performed at a micro-scale using detailed land use maps and geographic database. Eventually, based on a multidisciplinary work, the procedure may incorporate social flood impact analysis and evaluation of direct economic damage to different categories of buildings and land types. Besides detailing the characteristics and performance of the hazard modelling, the presentation will describe the flow of data within the overall risk analysis procedure and will demonstrate its applicability by means of a case study, for which three different flood protection measures have been evaluated. These include rehabilitation of an old canal, recalibration of a floodplain as well as heightening of a protection wall by means of mobile dikes. The risk-oriented analysis of these flood protection measures has lead to findings which would not have arisen from a more standard hydraulic study such as based on a design flood. The flood risk analysis procedure is now readily available for large scale applications throughout the hydrographic basins in Wallonia and, in the near future, it will be combined with catchment modelling (accounting for climate change projections) to evaluate upstream flood mitigation measures as well as for the fine tuning of reservoir management rules in the framework of adaptation strategies to climate change. [less ▲]

Experimental investigation of flow pattern and sediment deposition in rectangular shallow reservoirs

in International Journal of Sediment Research (2010), 25(3), 258-270

This work involved the experimental investigation of flow pattern, preferential regions of deposition and trap efficiency as a function of the length of rectangular shallow reservoirs. Four flow patterns ... [more ▼]

This work involved the experimental investigation of flow pattern, preferential regions of deposition and trap efficiency as a function of the length of rectangular shallow reservoirs. Four flow patterns were identified (from longer to shorter reservoirs): an asymmetric flow with two reattachment points, an asymmetric flow with one reattachment point, an unstable flow, and a symmetric flow without any reattachment point. Using dye visualizations, the median value and the temporal variability of the reattachment lengths were precisely measured for the asymmetric flows. For each stable flow, sediment tests with plastic particles were carried out. The regions of deposition on the bed of the reservoir were clearly a function of the flow pattern. The transition from an asymmetric flow pattern to a symmetric flow pattern was responsible for an abrupt decrease of the trap efficiency; a number of regression laws were discussed to take it into account. [less ▲]

Dam-break flow computation based on an efficient flux-vector splitting

in Journal of Computational & Applied Mathematics (2010), 234

Dam-break flow computation is a task of prime interest in the scope of risk analysis processes related to dams and reservoirs. In this paper, a 2D finite volume multiblock flow solver, able to deal with ... [more ▼]

Dam-break flow computation is a task of prime interest in the scope of risk analysis processes related to dams and reservoirs. In this paper, a 2D finite volume multiblock flow solver, able to deal with natural topography variation, is presented in details. The model is based on an efficient Flux Vector Splitting method developed by the authors. A number of validation examples are comprehensively described. [less ▲]

Proceedings of the International Symposium on Unsteady Sediment Transport - GESINUS 2010

Book published by University of Liege (2010)

Complexity in sediment transport and morphological modelling stems specifically from the variety of relevant physical processes as well as from their multi-scale nature, both in space (from grain- to ... [more ▼]

Complexity in sediment transport and morphological modelling stems specifically from the variety of relevant physical processes as well as from their multi-scale nature, both in space (from grain- to catchment scale) and in time (from quasi-instantaneous bank failures to silting of reservoirs within decades). To address this, the HACH group has developed a unique modelling system, which offers high flexibility in coupling flow and sediment transport sub-models to cover the broad spectrum of relevant time scales. In this framework, the HACH has convened on 29 and 30 July 2010 an international symposium, during which recent advances in morphological modelling have been presented, as well as progresses in grain scale experiments and field measurements. The symposium was supported by the University of Liege and the Fund for Scientific Research FNRS. Contributions from many European countries were presented and discussed, including Austria, Belgium, France, Italy, Netherlands, United Kingdom and Switzerland. [less ▲]

Analysis of climate change, high-flows and low-flows scenarios on the Meuse basin: WP1 report - Action 3

Report (2010)

Inondations en aval ... Impacts, risque et mesures de protection / gestion

Conference (2010, May 20)

Micro-scale flood risk analysis based on detailed 2D hydraulic modelling and high resolution geographic data

in Natural Hazards (2010), 55(2), 181-209

The paper presents a consistent micro-scale flood risk analysis procedure, relying on detailed 2D inundation modelling as well as on high resolution topographic and land use database. The flow model is ... [more ▼]

The paper presents a consistent micro-scale flood risk analysis procedure, relying on detailed 2D inundation modelling as well as on high resolution topographic and land use database. The flow model is based on the shallow-water equations, solved by means of a finite volume scheme on multiblock structured grids. Using highly accurate laser altimetry, the simulations are performed with a typical grid spacing of 2m, which is fine enough to represent the flow at the scale of individual buildings. Consequently, the outcomes of hydraulic modelling constitute suitable inputs for the subsequent exposure analysis, performed at a micro-scale using detailed land use maps and geographic database. Eventually, the procedure incorporates social flood impact analysis and evaluation of direct economic damage to residential buildings. Besides detailing the characteristics and performance of the hydraulic model, the paper describes the flow of data within the overall flood risk analysis procedure and demonstrates its applicability by means of a case study, for which two different flood protection measures were evaluated. [less ▲]

A 2D vertical model for incompressibleflows, using a level set free surface tracking

Poster (2010, May)

Steady and unsteady inundation modeling based on high resolution topographic data

Poster (2010, April 22)