2D Attenuation Model
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1 3 4 5 6 7 8 9 10 11 12 13 14 2 Flood-Exceedance Attenuation by Riparian Land-use Whitworth GA, Brasington JT, Yorke, L Contact: [email protected]
Transcript of 2D Attenuation Model
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Flood-Exceedance Attenuation by Riparian Land-use
Whitworth GA, Brasington JT, Yorke, LContact: [email protected]
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Contents
OverviewStudy Site
Flood Defence Background
Numerical ModelExperimental Farming
Software CalibrationAttenuation Gain
Conclusion
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Research Goals
• Sustainable Flood Defence
• Low Investment
• Low Impact
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Study SiteRiver Vyrnwy
River Severn
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Loss of lifeMore Background
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Study Site
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100km farmscale (‘Glastir’) streamside buffer-strips
100km community-maintained network of watercourses and hedges
40km Main River
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Point Cloud Assembly
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Munlyn-Buttington
DTM Points parallel to streamflow
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Parameters and ElementsTerrain Array
•(Munlyn – Buttington)
•Floodplain•Main River
•Maintained Courses•‘Glastir’ Courses
•Infrastructure
Depth and velocity parameters on a coarser set of flow elements
Elevation and roughness parameters on a finer Variable Terrain grid
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Flow Boundaries
Q = 0.05*H ^1.90
Flume Calibration
Buttington Channel/Weir Interface
MB Boundary Weir Equation
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Vegetation NetworksBaseline PastureStreamside Feature
Pseudo roughnessfor added flow resistance
Terrain grid overlaying Porous Frictional Weirs
Resistance by form
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Channel Flow – 100 cumecs
MB in-channel Calibration
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16000 36000 56000 76000 96000 116000 136000 156000
Seconds (from 0745 29Mar08)
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e (m
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But
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tage
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Mun (Mar08)
Mun (Model05)
Butt(Mar08)
Butt (Model05)
Buttington 29Mar2008
Buttington Model 0.05
Munlyn 29Mar2008
Munlyn model 0.05
Munlyn to ButtingtonChannel Calibration
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Overbank Flow - 400 cumecs2D output – ‘MB’ Flow Vectors overlaying water surface elevation
Pasture MaintainedStream-net
Maintained + Glastir
stream-nets
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+13% +23%+15%
Stream-nets +intermittent
Main-River friction
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Attenuation ResultsMB
ReachVolume
(m3^6)
% wet area (km2)
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Base 5.8 9.05
Streams 6.5 13 8.91 98
Streams and Buffers 6.7 15 8.95 99
Hi-mann-Form+Rough 7.1 23 9.13 101
Hi-mann-Form 6.7 15 8.92 98
Hi-mann-Rough 6.3 9 8.95 99
Munlyn-ButtngtonSample Points
Water-surface longsection over terrain
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Conclusions & Outcome
October 2000 Loss Peak
December 2000 Benign-Peak
• Flood Storage Gain• Low Lateral Impact• Exceedance control• Improved wellbeing
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Fin
Acknowledgements & thanksIGES, Aberystwyth UniversityRichard Williams, Jack Southon, Mark HubandEnvironment Agency Data TeamAlberta University River 2D codePowysland IDB BoardWAG Glastir (www.cymru.gov.uk/glastir)John Swogger [email protected] (Backdrop cartography)[Thomas et al], Assessment of Floodplain Woodland[Mandlburger et al], Optimisation of Lidar terrain models[Syme WJ], 2D Modelling of Buildings and Fences
Data
Analysis
Results
Outcome
Climate Research
Issues for a Model Catchment
Stakeholders
Boundaries
Porosity
Landuse
Topography Hydrometry
Parameters
Software
Hardware
Productivity
Method
Numerical
VirtualField-Tests
Real-timePublication
ExceedanceControl
Climate Research
A Model Catchment
Stakeholders
Boundaries
Porosity
Diversity
Physical-side Human-side
Parameters
Wellbeing
Blight
Funding
Land-usechange
Data
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Historic augment and Flood Frequency analysis suggest 2.5% exceedance at Pool Quay of
100cumecs x 16 hrs ~ 6,000,000m3
Say, 50% ~ 3,000,000m3 benign overspill
Leaving 50% ~ 3,000,000m3 additional Floodplain storage
Exceedance Stats
FEH
Upstream• 18% total storage
• 0.12m x 25km2
• (wind effect)
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3. Field Evidence
~ 200mm headloss
(~ 1:10yr event)
18Nov2009125mm head
Method Issues
• Point cloud strategy• Longitudinal arrays• Lateral arrays• Bathymetry• Discretization• Sub-reach no and length
Analysis Issues
• Steady State Flow• Dynamic Wave Flow• Experimental Terrain• Form v. Roughness•
Results Issues
• Attenuation Volume• Attenuation Time• Wet perimeter• Doorstep Elevation• Stage at High Risk Leveee
Outcome Issues
• Wellbeing • Ecology• Credibility & Transparency• Error & Uncertainty• Carbon• Visualization
Software Issues
• GIS linked assembly• EA standard 2D• FEM
• Conserve across domain • Value gradient across cell
• FVM• Conserve across cell • Quicker ??
Stakeholder Issues
• Government• LLFA• Environment Agenty• Land Drainage Authority• Landowners
Boundary Issues
• Inflow• Weir > Flo• Flume
• Tributaries• Wet/dry analysis
Porosity Issues
• Form• Roughness• Velocity instability• Froude number cap
Landuse Issues
• Glastir• Forestry• Farmside• IDB drainage• Infrastructure• Ecology
Topography Issues
• Point Cloud Structure• Long feature• Lateral Features• Discretization• Wrack data• Perimeter AP
Hydrometry Issues
• Time Series• Stochastic Inflow• Bathymetry
Parameter Issues
• River 2D coefficients• Roughess• Elevation• Velocity• Depth• Absorbence• Convergence• Solution Tolerance
Hardware Issues
• Single Core• Multi Core• GPU• Multi-thread
Productivity Issues
• 1:1• Resample confidence• Channel analysis• Overbank wave analysis
3. Field Evidence
c. 200mm headloss(~ 1:10yr event)
18Nov2009125mm head
