Post on 23-Feb-2016
description
Simplified hydraulic models for urban inundation modelling
Based on research by: Paul D. Bates1, Timothy J. Fewtrell1, Jeffrey C. Neal1, Mark A. Trigg1, Guy J-P. Schumann1 and Matthew S. Horritt2
1 School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK2 Halcrow Ltd., Burderop Park, Swindon, Wiltshire SN4 0QD, UK
Reduced complexity models of flooding
• Storage cell models originally created using irregular floodplain units (Zanobetti et al., 1970)
• Increased resolution of topographic data proliferated the development of regular grid versions in 2 dimensions
• Models either solve uniform flow formulae (e.g. Manning’s eqn) or finite difference approximation of diffusion wave (e.g. Bradbrook et al., 2004)
• Hunter et al. (2004) noted a number of problems with storage cell model type approach• If the time step was too large, “chequerboard” oscillations will
develop• Hunter et al. (2005) proposed a solution to these problems
by a von Neumann stability analysis of the diffusion wave equation
• However, as a result of the stability condition, computation time increases quadratically with increasing grid resolution
Computationally intractable for high resolution grids required for urban flood modelling
Testing: Planar surface
Model RMSE (m)
Volume Error (%)
Minimum Tstep (s)
Computation Time (s)
Speed up
Diffusive
0.06 1.27 0.15 0.33
Inertial 0.03 -1.27 7.25 0.02 17x
Testing: Wetting and drying
Testing: Model efficiency
Over 600x increase in time step → 1000x increase in computational speed
Model development: OpenMP
Application: Dead Run, Baltimore, US (July ‘04)
Application: Uncertain loss estimates
Application: Tewkesbury, UK (Summer ‘07)