Rahman khatibi ciwem_isis2_d

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This are the slides of my presentation on 3 December 2009 in an evening meeting organised by the CIWEM Southwest Branch.
Venue: Peter Brett Associates, Reading

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Rahman khatibi ciwem_isis2_d

  1. 1. The Practice of 2D FloodplainModelling: ISIS 2DDr Rahman KhatibiCentral Southern Branch - CIWEM3 December 2009Venue: Peter Brett Associates, ReadingThis presentation has the focus on:1. 2D modelling2. ISIS 2D3. Applications of ISIS 2D4. Future possibilities1 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khatibi
  2. 2. Setting the scene The ISIS 1D Model Objectives of 1D modelling: (i) depth h (ii) area-averaged variable u (Q) at all nodal points. The ISIS 2D Model Objectives of 2D modelling: (i) depth h (ii) depth-averaged variable u,v (qx, qy) at all grid points. TVD2 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  3. 3. Setting the scene Considering Flooding Risk from all sources Space scale Remote sensing Interfaces Modularity Meteorological models Time scale Data Gauges Modelling Global, regional, local Survey data LiDAR systems Survey data Time scale Surfacewate Space scale r models •0D Supercritical Subcritical Flow Hydrologic •1D regimes Kinematic Role waves models •1D+ Urban Rural Semi-urban Sewers •2D- Coastal models models (tides + surges) Land use •2DBrownfield Greenfield •2D+ Groundwate Reservoir failures New development r models models •3D Blockage Inundation Erosio Fluvial models Trigger events (channels + floodplains n Overtopping Breaching 3 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  4. 4. Summary1. What is 2D modelling?2. What is ISIS 2D?3. ISIS 2D applications4. Looking to the futureFocus on: • Modularity of modelling engines • Plurality in developing 2D solvers • Integration with GIS • Interfaces and their intuitiveness • Improved topographic data shifts uncertainty to roughness • Model management for their defensibility4 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  5. 5. 1. 2D Modelling – the technical details• Solves the Shallow Water Equations: Mass balanceInertia Convection Surface slope Bed friction Eddy viscosity• On a grid of square cells or unstructured mesh• Various solvers: e.g. ADI or TVD5 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  6. 6. 1. ADI Solver –Alternating Direction Implicit• Roots: uses the scheme given by Stelling (1984)• Numerical Scheme: • Reinvents 1D solvers in the 2D domain in each direction but staggered • Outcome – implicit solver (large time step)• Applicability: • Good for floodplain flows • Copes with most of breach problems• Limitations: Problems with supercritical flows  Water depth  x-component specific discharge  y-component specific discharge  Bed elevation6 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  7. 7. 1. TVD Solver - Total Variation Diminishing• Roots: McCormack scheme (1969)• Numerical Scheme: • Predictor-corrector – ensures numerical oscillations do not develop • Non-staggered – velocities are solved at cell centres• Applicability: • Subcritical and supercritical flows • Dambreak flows, • Spillways, • Breaching, • Steep surface water flows• Limitations: computationally intensive7 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  8. 8. 1. Simplified Mass Balance Schemes• Roots: Bates and Roo (2000)• So much for so little: • First come, first served + • Seeking for the lowest cell• Applicability: • Broad scale surface water risk assessment • Coastal inundation modelling • Modelling surface water from sewer surcharging• Limitations: completely ignores momentum8 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  9. 9. 1. Evolutionary background to 2D Modelling Fundamental thinking of 18th-19th Century18th-19thCentury Intellectual Capital of hydraulic Traditional component hydraulics 1900 Tapping on the intellectual capital By a fury of simplified methods •Empirical hydraulics 1950 •Design and operations 1960 •Advent of Computers •Hydrology •Rise of software engineering •Component analysis 1980 •Increasing data Tur 1D bul •Modelling practice 1990 enc em 3D 2D ode l l i ng 2000 Intelligent Emergence of flood risk management clients Modelling Beck: risk increasing Modelling and modelling 9 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  10. 10. 1. 2D versus 1D ModellingAdvantages of 1D: Barriers to 2D models before 2000 • Some vector data not much raster• Coping with many degrees of grid data freedom: gates, weirs, bridges, • Prohibitive model run times tributaries, abstractions Since 2000• Fast runs • Paradigm shift by LiDAR techDisadvantages: • Improved computational speed • TUFLOW at the place, right time• Artificially selecting flow paths – two examples• Defensibility of decisions on • Now: 1D survived besides 2D floodplain flow paths • Focus on uncertainty moved from data to others: e.g. hydrology, roughness • Opportunities for innovation1012/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  11. 11. 1. Flagging Salient Points: Modularity • Fast spreading • 0D • No equations • Longitudinal variations • Classic 2-stage channels • 1D • Continuity+ 1-momentum • Attenuating floodplains • 1D+ • Mass balance • Storage floodplains • 2D- • Mass balance + Diffusive FP • Slow overland flows • To model lateral variations • 2D • Continuity+ 2-momentum • Urban, coastal, floodplains • 2D+ • Continuity+ 2-momentum + a good solver • Hydraulic jumps/Roll waves • 3D • Mixing required • Continuity+ 3-momentum Opportunities for innovation •Modularity in modelling engines •Each 2D solver has a selective advantage •Focus on uncertainty shifted from data to … •Model management for defensibility 1112/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  12. 12. 2. ISIS 2D – Background• Capability: ISIS 2D uses the Shallow Water Equations• Roots: DIVAST by Prof. Falconer - Cardiff University• Applicable to: • fluvial floodplains • coastal floodplains • natural channels, • surface water flows, • spillways etc.• Part of the ISIS Suite1212/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  13. 13. 2. The ISIS Suite• Integrated with ISIS Mapper for • pre-processing and • post-processing • Other GIS packages may be used• ISIS (1D)• OpenMI1312/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  14. 14. 2. ISIS 2D DomainsDomains and Schematisation Contours Road 2D Domain 1 Embedded Extended 1D 1D Model High Sections Resolution Flood Relieve Channels1D Reservoir 2D Domain 3 2D Domain 2 Low Resolution Medium Resolution Contours1412/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  15. 15. 2. ISIS2D Modelling – the InterfaceFor each domains: • Grid data • Boundary conditions • Hydrology • Run details – select the solver • Output details1512/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  16. 16. 2. DataData management:1. ASCII raster for grid, (DTM)2. Shapefiles for vector • Active areas • Position of boundary conditions • 1D/2D Linkage lines3. Textfiles for hydrographs • Boundary inputs • Some of the outputs4. Binary Outputs• Intuitive folder structures and not many files1612/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  17. 17. 2. Load DTM1712/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  18. 18. 2. Define active area1812/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  19. 19. 2. Define boundary condition vectors1912/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  20. 20. 2. Add topography vector data2012/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  21. 21. 2. Running 2D Interface2112/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  22. 22. 2. Visualise Results2212/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  23. 23. 2. Flagging salient points ISIS philosophy to innovation: •Modularity of modelling engines •Solver status: ADI and TVD – released ISIS FAST – to be released ISIS FAST A cellular solver – planned •Integrated with GIS •Ease of use by intuitive interfaces •Model management for defensibility2312/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  24. 24. 3. ISIS 2D Applications• In-house benchmarking tests for all three solvers• Just completed the EA’s 2D model benchmarking tests – evaluation at Herriot-Watt University• Wide applications to project works• ADI Speed: comparable to TUFLOW or better• TVD is slower due to small time steps required2412/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  25. 25. 3. ADI: Example 1 – Reservoir breach• Description of the model: • Location: a town somewhere in Wiltshire • Trigger event: reservoir breach• Model description: description • Data as shown before • Used a global roughness value• Run the model and analyse the results • Use the ADI solver ADI2512/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  26. 26. 3. ADI: Example 2 – River Severn at Upton • Linked 1D-2D model • Channel – floodplain exchanges over bank and through culverts A DIThis is similar to the benchmarking test set by the EA andthe project is run by Herriot Watt University. Halcrow’sthanks are due to both EA and Herriot Watt University. 2612/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  27. 27. ADI: Example 2 – River Severn at Upton2712/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  28. 28. 3. TVD: Classic hydraulics – Hydraulic jumps2812/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  29. 29. TVD: Example 1 – Laboratory flume dambreak (FP5 IMPACT Project)These validation data were produced by the European IMPACT project (see Soares-Frazao and Zech, 2007). Halcrow wish tothank the researchers and funders involved with this project for making their data freely available to all. Furtherinformation is available from www.impact-project.net and in a special edition of the Journal of Hydraulics Researchpublished in 2007. 2912/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  30. 30. These validation data were produced by the European IMPACT project (see Soares-Frazao and Zech, 2007). Halcrow wish to thank the researchers andfunders involved with this project for making their data freely available to all. Further information is available from www.impact-project.net and in aspecial edition of the Journal of Hydraulics Research published in 2007. 3012/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  31. 31. These validation data were produced by the European IMPACT project (see Soares-Frazao and Zech, 2007). Halcrow wish to thank the researchers andfunders involved with this project for making their data freely available to all. Further information is available from www.impact-project.net and in aspecial edition of the Journal of Hydraulics Research published in 2007. 3112/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  32. 32. These validation data were produced by the European IMPACT project (see Soares-Frazao and Zech, 2007). Halcrow wish to thank the researchers andfunders involved with this project for making their data freely available to all. Further information is available from www.impact-project.net and in aspecial edition of the Journal of Hydraulics Research published in 2007. 3212/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  33. 33. These validation data were produced by the European IMPACT project (see Soares-Frazao and Zech, 2007). Halcrow wish to thank the researchers andfunders involved with this project for making their data freely available to all. Further information is available from www.impact-project.net and in aspecial edition of the Journal of Hydraulics Research published in 2007. 3312/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  34. 34. These validation data were produced by the European IMPACT project (see Soares-Frazao and Zech, 2007). Halcrow wish to thank the researchers andfunders involved with this project for making their data freely available to all. Further information is available from www.impact-project.net and in aspecial edition of the Journal of Hydraulics Research published in 2007. 3412/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  35. 35. 3. TVD: Example 1 – Laboratory flume dambreak (FP5 IMPACT Project)3512/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  36. 36. 3. An example from ISIS FAST Area of Interest Digital Terrain ModelThese data were provided by FCC/OPW. Halcrow wish to thank the client for allowing to use their data. The resultsproduced here are hypothetical and just for demonstration purpose. The client has given permission for using the data fordemonstration purpose but without approving the results. 3612/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  37. 37. 3. An example from ISIS FAST Results (Depths) OverlaidThese data were provided by FCC/OPW. Halcrow wish to thank the client for allowing to use their data. The resultsproduced here are hypothetical and just for demonstration purpose. The client has given permission for using the data fordemonstration purpose but without approving the results. 3712/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  38. 38. 3. An example from ISIS FASTThese data were provided by FCC/OPW. Halcrow wish to thank the client for allowing to use their data. The resultsproduced here are hypothetical and just for demonstration purpose. The client has given permission for using the data fordemonstration purpose but without approving the results. 3812/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  39. 39. 3. ADI, TVD or Raster Routing? – horses for courses AD TV I DThis is similar to the benchmarking test set by the EA and the project is run by Herriot Watt University. Halcrow’s thanks aredue to both EA and Herriot Watt University. 3912/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  40. 40. 3. ADI and TVD: Surface water flooding in Glasgow s ve llwa Ro Red blobs show Froude No >1 Two flow case: 1. Rainfall -ADI 2. Sewer flood - TVDThis is similar to the benchmarking test set by the EA and the project is run by Herriot Watt University. Halcrow’s thanksare due to both EA and Herriot Watt University. 4012/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  41. 41. 3. Flagging Salient Topics Observations: we saw in action •Modularity of modelling engines •Different 2D solvers – “horses for courses” •Integration of modelling engines with GIS •Intuitive interfaces •The ease to gain an insight into problems •The focus on uncertainty shifted from topographic data to roughness and other factors •Model management is taking a new meaning4112/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  42. 42. 4. Future developments• Cellular flow model – quicker solution for many floodplain problems• FAST model – simple hydraulics for rapid surface water analysis• Implicit linking of 1D and 2D domains – improved stability• Direct linking of multiple domains – allows nesting of high resolution areas• 2D water quality4212/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
  43. 43. 5. Conclusion• Innovation in 2D Modelling has a positive effect on flood risk management, including: • Reduced uncertainty due to topographic details • Efficiency of modelling studies • The ability to gain an insight into problems • Improved defensibility of models • New dimensions in model management4312/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat

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