Influence of Detailed Topography when Modeling Flows in Street Junction During Urban Flood
Pierre-Henri Bazin*, Anne Bessette**, Emmanuel Mignot**,
André Paquier*, and Nicolas Rivière**
*Hydrology Hydraulics Research Unit (HHLY), National Research Institute of Science and Technology for Environment and Agriculture (Irstea), 3 bis quai Chauveau CP220, 69336 Lyon cedex09, France
**Fluid Mechanics and Acoustics Laboratory (LMFA), CNRS-Universite de Lyon, INSA de Lyon, Bat. Joseph Jacquard, 20 avenue A. Einstein, 69621 Villeurbanne Cedex, France
Floods in dense urban areas propagatemainly through the streets, where the flow can be locally affected by elements of urban topography. This study aims at assessing the need of integrating detailed topography in numerical models when simulating urban floods. Acoustic Doppler Velocimetry and Large Scale Particle Image Velocimetry measurements in an experimental three branch junction representing a city crossroad are used to calibrate a numerical model solving the 2D shallow water equations. A constant eddy viscosity model proves to be accurate enough to calculate velocity fields, but such model requires a fine calibration against experimental data. Simulations run with this calibrated model are performed to study the impact of obstacles and sidewalks representative of urban areas. It is found that obstacles located in the downstream branch can highly perturb the velocities distribution downstream of the junction, whereas obstacles located in the upstream branches have less influence. The presence of sidewalks results in reduced flow section and higher velocities, but additional effects occur within and downstream of the junction. Simulations presented here show the need of considering detailed topography and elements of urban furniture if local velocities have to be represented.
André Paquier, and Nicolas Rivière, “Influence of Detailed Topography when Modeling Flows in Street Junction During Urban Flood,” J. Disaster Res., Vol.7, No.5, pp. 560-566, 2012.
-  E. Mignot, A. Paquier, and S. Haider, “Modeling floods in a dense urban area using 2D shallow water equations,” Journal of Hydrology, Vol.327, Nos.1-2, pp. 186-199, 2006.
-  D. Yu and S. N. Lane, “Urban fluvial flood modelling using a twodimensional diffusion-wave treatment, part 1: mesh resolution effects,” Hydrological Processes, Vol.20, No.7, pp. 1541-1565, 2006.
-  Z. Vojinovic and D. Tutulic, “On the use of 1D and coupled 1D-2D modelling approaches for assessment of flood damage in urban areas,” Urban Water Journal, Vol.6, No.3, pp. 183-199, 2009.
-  J. E. Schubert, B. F. Sanders et al., “Unstructured mesh generation and landcover-based resistance for hydrodynamic modeling of urban flooding,” Advances in Water Resources, Vol.31, No.12, pp. 1603-1621, 2008.
-  L. J. Weber, E. D. Schumate, and N. Mawer, “Experiments on flow at a 90° open-channel junction,” Journal of Hydraulic Engineering, Vol.127, No.5, pp. 340-350, 2001.
-  N. M. Hunter, P. D. Bates, S. Neelz, G. Pender, I. Villanueva, N. G. Wright, D. Liang, R. A. Falconer, B. Lin, S. Waller, A. J. Crossley, and D. C. Mason, “Benchmarking 2D hydraulic models for urban flooding,” Proceedings of the Institution of Civil Engineers-Water Management, Vol.161, No.11, pp. 13-30, 2008.
-  J. Le Coz, A. Hauet, G. Pierrefeu, G. Dramais, and B. Camenen, “Performance of image-based velocimetry (LSPIV) applied to flash-flood discharge measurements in Mediterranean rivers,” Journal of Hydrology, Vol.394, Nos.1-2, pp. 42-52, 2010.