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Rahman khatibi ciwem_isis2_d
- 1. The Practice of2D Floodplain Modelling: ISIS 2D Dr Rahman Khatibi Central Southern Branch - CIWEM 3 December 2009 Venue: Peter Brett Associates, Reading This presentation has the focus on: 1. 2D modelling 2. ISIS 2D 3. Applications of ISIS 2D 4. Future possibilities 1 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khatibi
- 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. TVD 2 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 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 •2D Brownfield 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. Summary 1. What is2D modelling? 2. What is ISIS 2D? 3. ISIS 2D applications 4. Looking to the future Focus 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 defensibility 4 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 5. 1. 2D Modelling – the technical details • Solves the Shallow Water Equations: Mass balance Inertia Convection Surface slope Bed friction Eddy viscosity • On a grid of square cells or unstructured mesh • Various solvers: e.g. ADI or TVD 5 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 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 elevation 6 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 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 intensive 7 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 8. 1. Simplified MassBalance 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 momentum 8 12/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 9. 1. Evolutionary backgroundto 2D Modelling Fundamental thinking of 18th-19th Century 18th-19th Century 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. 1. 2D versus1D Modelling Advantages 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 tech Disadvantages: • 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 innovation 1012/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 11. 1. Flagging SalientPoints: 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. 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 Suite 1212/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 13. 2. The ISISSuite • Integrated with ISIS Mapper for • pre-processing and • post-processing • Other GIS packages may be used • ISIS (1D) • OpenMI 1312/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 14. 2. ISIS 2DDomains Domains and Schematisation Contours Road 2D Domain 1 Embedded Extended 1D 1D Model High Sections Resolution Flood Relieve Channels 1D Reservoir 2D Domain 3 2D Domain 2 Low Resolution Medium Resolution Contours 1412/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 15. 2. ISIS2D Modelling– the Interface For each domains: • Grid data • Boundary conditions • Hydrology • Run details – select the solver • Output details 1512/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 16. 2. Data Data management: 1.ASCII raster for grid, (DTM) 2. Shapefiles for vector • Active areas • Position of boundary conditions • 1D/2D Linkage lines 3. Textfiles for hydrographs • Boundary inputs • Some of the outputs 4. Binary Outputs • Intuitive folder structures and not many files 1612/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 17. 2. Load DTM 1712/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 18. 2. Define activearea 1812/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 19. 2. Define boundarycondition vectors 1912/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 20. 2. Add topographyvector data 2012/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 21. 2. Running 2DInterface 2112/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 22. 2. Visualise Results 2212/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 23. 2. Flagging salientpoints 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 defensibility 2312/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 24. 3. ISIS 2DApplications • 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 required 2412/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 25. 3. ADI: Example1 – 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 ADI 2512/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 26. 3. ADI: Example2 – River Severn at Upton • Linked 1D-2D model • Channel – floodplain exchanges over bank and through culverts A DI This is similar to the benchmarking test set by the EA and the project is run by Herriot Watt University. Halcrow’s thanks are due to both EA and Herriot Watt University. 2612/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 27. ADI: Example 2– River Severn at Upton 2712/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 28. 3. TVD: Classichydraulics – Hydraulic jumps 2812/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 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 to thank the researchers and funders involved with this project for making their data freely available to all. Further information is available from www.impact-project.net and in a special edition of the Journal of Hydraulics Research published in 2007. 2912/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 30. These validation datawere produced by the European IMPACT project (see Soares-Frazao and Zech, 2007). Halcrow wish to thank the researchers and funders involved with this project for making their data freely available to all. Further information is available from www.impact-project.net and in a special edition of the Journal of Hydraulics Research published in 2007. 3012/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 31. These validation datawere produced by the European IMPACT project (see Soares-Frazao and Zech, 2007). Halcrow wish to thank the researchers and funders involved with this project for making their data freely available to all. Further information is available from www.impact-project.net and in a special edition of the Journal of Hydraulics Research published in 2007. 3112/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 32. These validation datawere produced by the European IMPACT project (see Soares-Frazao and Zech, 2007). Halcrow wish to thank the researchers and funders involved with this project for making their data freely available to all. Further information is available from www.impact-project.net and in a special edition of the Journal of Hydraulics Research published in 2007. 3212/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 33. These validation datawere produced by the European IMPACT project (see Soares-Frazao and Zech, 2007). Halcrow wish to thank the researchers and funders involved with this project for making their data freely available to all. Further information is available from www.impact-project.net and in a special edition of the Journal of Hydraulics Research published in 2007. 3312/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 34. These validation datawere produced by the European IMPACT project (see Soares-Frazao and Zech, 2007). Halcrow wish to thank the researchers and funders involved with this project for making their data freely available to all. Further information is available from www.impact-project.net and in a special edition of the Journal of Hydraulics Research published in 2007. 3412/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 35. 3. TVD: Example1 – Laboratory flume dambreak (FP5 IMPACT Project) 3512/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 36. 3. An example from ISIS FAST Area of Interest Digital Terrain Model These data were provided by FCC/OPW. Halcrow wish to thank the client for allowing to use their data. The results produced here are hypothetical and just for demonstration purpose. The client has given permission for using the data for demonstration purpose but without approving the results. 3612/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 37. 3. An examplefrom ISIS FAST Results (Depths) Overlaid These data were provided by FCC/OPW. Halcrow wish to thank the client for allowing to use their data. The results produced here are hypothetical and just for demonstration purpose. The client has given permission for using the data for demonstration purpose but without approving the results. 3712/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 38. 3. An examplefrom ISIS FAST These data were provided by FCC/OPW. Halcrow wish to thank the client for allowing to use their data. The results produced here are hypothetical and just for demonstration purpose. The client has given permission for using the data for demonstration purpose but without approving the results. 3812/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 39. 3. ADI, TVDor Raster Routing? – horses for courses AD TV I D This is similar to the benchmarking test set by the EA and the project is run by Herriot Watt University. Halcrow’s thanks are due to both EA and Herriot Watt University. 3912/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 40. 3. ADI andTVD: Surface water flooding in Glasgow s ve llwa Ro Red blobs show Froude No >1 Two flow case: 1. Rainfall -ADI 2. Sewer flood - TVD This is similar to the benchmarking test set by the EA and the project is run by Herriot Watt University. Halcrow’s thanks are due to both EA and Herriot Watt University. 4012/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 41. 3. Flagging SalientTopics 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 meaning 4112/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 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 quality 4212/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat
- 43. 5. Conclusion • Innovationin 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 management 4312/23/12 The Practice of 2D Floodplain Modelling: ISIS 2D - Rahman Khat