1 / 32

Contents

Flood-wave Attenuation by Farmed Valley-floor Stiff-Vegetation Whitworth GA, Brasington JT, Yorke, L Contact: gaw1@cantab.net. Contents. Overview Study Site Flood Defence Background Numerical Model Experimental Farming Software Calibration Attenuation Gain Conclusion. Research Goals.

oberon
Download Presentation

Contents

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Flood-wave Attenuation by FarmedValley-floor Stiff-VegetationWhitworth GA, Brasington JT, Yorke, LContact: gaw1@cantab.net

  2. Contents Overview Study Site Flood Defence Background Numerical Model Experimental Farming Software Calibration Attenuation Gain Conclusion

  3. Research Goals • Sustainable Flood Defence • Low Investment • Low Impact

  4. Study Site River Vyrnwy River Severn

  5. Loss of life More Background

  6. Study Site 100km farmscale (‘Glastir’) streamside buffer-strips R 40km Main River A 100km community-maintained network of watercourses and hedges

  7. Point Cloud Assembly R DTM Points parallel to streamflow B Munlyn-Buttington M C A

  8. Parameters and Elements • Terrain Array • (Munlyn – Buttington) • Floodplain • Main River • Maintained Courses • ‘Glastir’ Courses • Infrastructure • Depth and velocity parameterson a coarser set of flow elements Elevation and roughness parameters on a finer Variable Terrain grid

  9. Flow Boundaries Buttington Channel/Weir Interface Q = 0.05*H ^1.90 • MB Boundary Weir Equation Flume Calibration

  10. Vegetation Networks Resistance by form Streamside Feature Baseline Pasture Terrain grid overlaying Porous Frictional Weirs Pseudo roughness for added flow resistance

  11. Channel Flow – 100 cumecs • Munlyn model 0.05 Buttington Model 0.05 Munlyn to Buttington Channel Calibration • Munlyn • 29Mar2008 Buttington 29Mar2008

  12. Overbank Flow - 400 cumecs 2D output – ‘MB’ Flow Vectors overlaying water surface elevation +13% +15% +23% 0% Stream-nets + intermittent Main-River friction Maintained + Glastir stream-nets Maintained Stream-net Pasture

  13. Attenuation Results Munlyn-Buttngton Sample Points Water-surface longsection over terrain

  14. Conclusions & Outcome • Flood Storage Gain • Low Lateral Impact • Exceedance control • Improved wellbeing October 2000 Loss Peak December 2000 Benign-Peak

  15. Fin Acknowledgements & thanks IGES, Aberystwyth University Richard Williams, Jack Southon, Mark Huband Environment Agency Data Team Alberta University River 2D Team Powysland IDB Board WAG Glastir (www.cymru.gov.uk/glastir) [Thomas et al], Assessment of Floodplain Woodland [Mandlburger et al], Optimisation of Lidar terrain models [Syme WJ], 2D Modelling of Buildings and Fences John Swogger (Catchment backdrop)

  16. Research Climate Issues for a Model Catchment Data Topography Hydrometry Landuse Parameters Porosity Method Software Boundaries Analysis Stakeholders Hardware Results Productivity Outcome

  17. Exceedance Stats FEH • Upstream • 18% total storage • 0.12m x 25km2 • (wind effect) Historic augment and Flood Frequency analysis suggest 2.5% exceedance at Pool Quayof 100cumecs x 16 hrs ~ 6,000,000m3 Say, 50% ~ 3,000,000m3 benign overspill Leaving 50% ~ 3,000,000m3 additional Floodplain storage

  18. 3. Field Evidence 18Nov2009 125mm head ~ 200mm headloss (~ 1:10yr event)

  19. Method Issues • Point cloud strategy • Longitudinal arrays • Lateral arrays • Bathymetry • Discretization • Sub-reach no and length

  20. Analysis Issues • Steady State Flow • Dynamic Wave Flow • Experimental Terrain • Form v. Roughness

  21. Results Issues • Attenuation Volume • Attenuation Time • Wet perimeter • Doorstep Elevation • Stage at High Risk Leveee

  22. Outcome Issues • Wellbeing • Ecology • Credibility & Transparency • Error & Uncertainty • Carbon • Visualization

  23. Software Issues • GIS linked assembly • EA standard 2D • FEM • Conserve across domain • Value gradient across cell • FVM • Conserve across cell • Quicker ??

  24. Stakeholder Issues • Government • LLFA • Environment Agenty • Land Drainage Authority • Landowners

  25. Boundary Issues • Inflow • Weir > Flo • Flume • Tributaries • Wet/dry analysis

  26. Porosity Issues • Form • Roughness • Velocity instability • Froude number cap

  27. Landuse Issues • Glastir • Forestry • Farmside • IDB drainage • Infrastructure • Ecology

  28. Topography Issues • Point Cloud Structure • Long feature • Lateral Features • Discretization • Wrack data • Perimeter AP

  29. Hydrometry Issues • Time Series • Stochastic Inflow • Bathymetry

  30. Parameter Issues • River 2D coefficients • Roughess • Elevation • Velocity • Depth • Absorbence • Convergence • Solution Tolerance

  31. Hardware Issues • Single Core • Multi Core • GPU • Multi-thread

  32. Productivity Issues • 1:1 • Resample confidence • Channel analysis • Overbank wave analysis

More Related