Predicting the flow in the floodplains with evolving land occupations during extreme flood events (FlowRes ANR project)

¹ Irstea, Unité de Recherche Hydrologie-Hydraulique, 5 rue de la Doua CS70077 69626 Villeurbanne cedex, France
² Laboratoire de Mécanique des Fluides et d’Acoustique, 20 av. A. Einstein, 69621 Villeurbanne cedex, France
³ Institut de Mécanique des Fluides de Toulouse, 2 allée du professeur Camille Soula, 31400 Toulouse, France
⁴ Laboratoire d’Hydraulique Saint-Venant (LHSV), 6 quai Watier, BP 49 78401 Chatou
⁵ CERIS, Instituto Superior Técnico, Universidade de Lisboa, 1 av. Rovisco Pais, CP 1049-001, Lisbon, Portugal
⁶ Laboratorio Nacional de Engenharia Civil, 101 Av. do Brasil, CP 1700-066, Lisboa, Portugal
⁷ Universitetet i Agder, Jon Lillietunsvei 9, CP 4879, Grimstad, Norway
⁸ Université catholique de Louvain, 1 bte L.05.01, Place du Levant, CP 1348, Louvain-la-Neuve, Belgium
⁹ Service Public de Wallonie, SPW-DO.222, 164 rue de l’Abattoir, 6200 Châtelet, Belgium
¹⁰ Eidgenössische Technische Hochschule Zürich, Zurich, Switzerland
¹¹ Karlsruher Institut für Technologie, Karlrühe, Germany

^a Corresponding author: sebastien.proust@irstea.fr

Abstract

Flood hazards (flow depth and velocity) must be accurately assessed in high-risk areas during extreme flood events. However, the prediction of the very high flows is not an easy task due to the lack of field data and to the strong link between flow resistance and the land occupation of the floodplain. Confinement and inhomogeneity in lateral and longitudinal directions of hydraulic roughness strongly vary with return period T. The physical processes are complex, some still largely unexplored, and the assumptions linked to numerical modelling cannot be validated without field data. The FlowRes project (2015-2018), funded by the French National Research Agency (ANR), aims at improving the flood hazard assessment in floodplains in: 1) investigating in laboratory the hydrodynamic structure associated with extreme flood flows for various land occupations and flow discharge magnitudes; 2) assessing if the existing numerical modelling practices used for T ~ 100 years are still valid for extreme events with T > 1000 years, relying on the experimental data and on one field case. This paper reports some results obtained during the first year of the project.