Articles | Volume 16, issue 6
Nat. Hazards Earth Syst. Sci., 16, 1413–1429, 2016
Nat. Hazards Earth Syst. Sci., 16, 1413–1429, 2016

Research article 16 Jun 2016

Research article | 16 Jun 2016

Hydrodynamics of long-duration urban floods: experiments and numerical modelling

Anaïs Arrault1,3, Pascal Finaud-Guyot2, Pierre Archambeau1, Martin Bruwier1, Sébastien Erpicum1, Michel Pirotton1, and Benjamin Dewals1 Anaïs Arrault et al.
  • 1Research group HECE, Department ArGEnCo, University of Liege, Liege, Belgium
  • 2ICube, Université de Strasbourg, CNRS – UMR7357, ENGEES, 2 rue Boussingault, Strasbourg, France
  • 3Ecole Nationale Supérieure des Mines d'Ales, 6 Avenue de Clavières 30319 Ales CEDEX, France

Abstract. Flood risk in urbanized areas raises increasing concerns as a result of demographic and climate changes. Hydraulic modelling is a key component of urban flood risk analysis; yet, detailed validation data are still lacking for comprehensively validating hydraulic modelling of inundation flow in urbanized floodplains. In this study, we present an experimental model of inundation flow in a typical European urban district and we compare the experimental observations with predictions by a 2-D shallow-water numerical model. The experimental set-up is 5 m  ×  5 m and involves seven streets in each direction, leading to 49 intersections. For a wide range of inflow discharges, the partition of the measured outflow discharges at the different street outlets was found to remain virtually constant. The observations also suggest that the street widths have a significant influence on the discharge partition between the different streets' outlets. The profiles of water depths along the streets are mainly influenced by the complex flow processes at the intersections, while bottom roughness plays a small part. The numerical model reproduces most of the observed flow features satisfactorily. Using a turbulence model was shown to modify the length of the recirculations in the streets, but not to alter significantly the discharge partition. The main limitation of the numerical model results from the Cartesian grid used, which can be overcome by using a porosity-based formulation of the shallow-water equations. The upscaling of the experimental observations to the field is also discussed.

Short summary
Floods in urban environments cause substantial damage. Urban flood risk management requires a reliable knowledge of flood hazard, including the flow characteristics in urbanized floodplains. Here we present numerical simulations of flooding in an urban district. The computations are compared against experimental observations obtained from a remarkable laboratory set-up, representing an urban district with 14 streets and 49 crossroads. Data provide a unique benchmark for other numerical models.
Final-revised paper