Results compare flood map and water level

PRESENTATION PLAN Introduction: Programme of the week Methodology Data used Software 1D (MIKE 11, ISIS, HEC-RAS) Software 2D (MIKE 21, MIKE 21FM, TELEMAC 2D) Comparison of software Conclusions 11 21 21 FM

PROGRAMME OF THE WEEK Prepare data

METHODOLOGY

DATA USED Study zone → Lower Var (6300 m of river from sea) - Period → Flood event 2011- From 04/11/2011 to 11/11/2011 DEM → 15m resolution Upper boundary condition → Hydrograph in La Manda bridge (peak discharge = 1200m3/s) Lower boundary condition → Sea level Roughness coefficient → 20 (Strickler) = 0,05 (Manning)

SOFTWARE 1D 11

Hydraulic structures (e.g. weirs) SOFTWARE 1D All based on the equations of mass and momentum conservation Software Numerical method Represents Principal parameter Output Hydraulic structures (e.g. weirs) Implicit Finite Difference (6p Abbot) Unsteady & Steady Manning's roughness (n) Topography (cross sections) Water depth Flood extent YES ISIS Explicit Finite Difference (Preissmann 4p box scheme) Steady & Unsteady (with instabilities) Manning's roughness (n) --> Parameter k Flow velocity* HEC Ras (Preissmann 2nd order box scheme) Roughness height (k) Flow velocity Finite Volumes (Roe) Geometry Network Boundary Conditions Discharge 11 MASCARET

Observed Stage and Discharge Peaks at about 135 hours, and 2.35 m

MIKE 11 - Results Water depth Discharge 11

ISIS - Results Water depth Discharge

HEC-RAS - Results Water depth Flood extent 05/11/2011 11h00

SOFTWARE 2D 21 21 FM

SOFTWARE 2D Software Numerical method Well adapted to SWE properties Structured spatial discretization Optimization of computational points Time needed (relative) Flow regime changes Structures (e.g. weirs) based on: Possible mass creation Finite Differences (ADI) NO YES Good Stable Not accurate (e.g. flow regime changes) Topography or Empirical formulas Finite Volumes (Roe) Reasonable Stable; not accurate Topography/ Empirical formulas TELEMAC 2D Finite Elements (SUPG) 21 21 FM Abily et al. 2016

Model Characteristics MIKE 21- Results Model Characteristics Flood map Specific boundary is applied along the borders Fill the void with a specific data Only structured mesh Run once to simulate IC (10 min) Create a storage in upstream Create a pool in downstream Fill the void with a specific data : Les bords sont définis par 9999 et la mer par -5 Create a storage in upstream : Creation d’un bassin d’alimentation à l’amont pour que le debit soit directement injecté dans le cours d’eau 21

Model Characteristics MIKE 21 FM - Results Model Characteristics Flood map Use structured or unstructured mesh Water level, discharge and velocities No weir 1 due to DTM Have to create a pool Run once to generate IC (20mn) Triangle de 100m de côté dans la mer, 25m dans la plaine alluviale et 15 dans le lit mineur 21 FM

Model Characteristics TELEMAC 2D- Results Model Characteristics Flood map Water level and velocities No weir 1 due to DTM Hard to implement the weir Low data flexibility Use of Bluekenue (Build mesh + Visualize) - Parameter file hard to build

COMPARISON OF SOFTWARE 11 COMPARISON OF SOFTWARE 21 21 FM

Comparison of water depth at Napoleon III bridge (1D) Software Highest water depth Time of occurrence MIKE 11 0.3 m 05/11/2011 11h00 ISIS 4.75 m 05/11/2011 20h00 HEC-RAS 2.5 m Derived from results shown in prior slides

Comparison of water level time-series trend (1D) MIKE 11 ISIS HEC-RAS Quite similar graph shape for all ID model simulations

Comparison of water depth at the same time (2D) Mike 21 Mike 21 FM Telemac

Comparison of velocity at the same time (2D) Mike 21 Mike 21 FM Telemac

Comparison of velocity at the same time (2D) Mike 21 Mike 21 FM Telemac

Flood Location (1D & 2D) HEC-RAS and 2D softwares 2D Softwares and HEC-RAS Telemac 2D and HEC-RAS Where we see the floods Mike11: the water level is too low there is no floods. May be too much instabilities in the model.

Time of Flood Appearance Software When the first flood appears At CAP 3000 South of the Airport Mike 21 04/11/2011 23h00 05/11/2011 02h00 TELEMAC 2D 04/11/2011 15h00 04/11/2011 14h30 Mike 21 FM 04/11/2011 17h00 HEC-RAS 05/11/2011 00h00 05/11/11 06h00 The water level is around 0.2m at the begenning of the first flood and reach around 1 to 1.5m at the peak.

Time for Simulation Mike 11 15 ISIS 10 HEC-RAS 3 Mike 21 300 Model Time (min) Mike 11 15 ISIS 10 HEC-RAS 3 Mike 21 300 Mike 21 FM 200 Telemac 2D 350 Mike21FM_temps de simulation 200min

11 CONCLUSIONS 21 21 FM

CONCLUSIONS 2D models are able to represent the floodplain better Telemac takes more time to simulate but gives more accurate results in comparison to Mike 21 and Mike 21 FM. - Differences between water levels - Differences between the time when the flood occurs - 1D models are greatly affected by cross-section geometry. Real bathymetry data give better results

REFERENCES Abyli et al (2016). Procedia Engineering / 154 / 2016 “High-resolution Modelling With Bi-dimensional Shallow Water Equations Based Codes – High-Resolution Topographic Data Use for Flood Hazard Assessment Over Urban and Industrial Environments” by Abily Morgan, Delestre Olivier, Bertrand Nathalie, Duluc Claire-Marie and Gourbesville Philippe. HEC-RAS Manual, Hydrologic Engineering Center, River Analysis System ISIS help. http://help.floodmodeller.com/isis/ISIS.htm Roe, P. (1981, October). Approximate riemann solvers, parameter vectors and difference schemes. Journal of Computational Physics 43(2), 357–372. Abbot et al. (1967). Abbott, M. B. and Ionescu, F.: On The Numerical Computation Of Nearly Horizontal Flows, J. Hydraul. Res., 5, 97–117 Preissmann, A. (1961). Propagation des intumescences dans les canaux et rivieres. In `1er congres de l’Association Franc¸aise de Calcul`, Grenoble, France. MIKE 21 & MIKE 3 FLOW MODEL FM. Hydrodynamic and Transport Module. Scientific Documentation “Review of Hydraulic Flood Modeling Software used in Belgium, The Netherlands, and The United Kingdom” Daniel Gilles and Matthew Moore August 15th, 2010 International Perspectives in Water Resource Management IIHR – Hydroscience & Engineering University of Iowa, College of Engineering. Brooks (1982).Brooks AN, Hughes TJR. Streamline upwind Petrov {Galerkin formulations for convection dominated ows with particular emphasis on the incompressible Navier{Stokes equations. Computer Methods in Applied Mechanics and Engineering 1982; 32: 199-259. Hervouet (2007). Hydrodynamics of Free Surface Flows, Modelling with the Finite-element Method. John Wiley & Sons Ltd., West Sussex, England (2007) 340 pp

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