intro to hec-ras 2d - latornell conservation symposium · intro to hec-ras 2d case study on the...
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Intro to HEC-RAS 2DCase Study on the Speed River
Ning PanSchool of EngineeringUniversity of Guelph
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Outline 2D modelling in HEC-RAS 5.0 (beta
version) Dam break study (Speed River) 1D vs. 2D Steady State 2D Evaluation Conclusions
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1D modelling in HEC-RAS It has been widely used for 20 years
(HEC-2 for 30 years before this)
Application: rivers, channels, structures
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1D Modelling in HEC-RAS Both steady and unsteady state
One-dimensional limitations Simplifications in the geometry No change in water elevation within a XS Instability problems
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2D Modelling in HEC-RAS Incorporates more available data(e.g. Terrain model, land cover GIS)
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2D Modelling in HEC-RAS Removes some limitations: e.g. same water elevation within a x-
section Improve stability and robustness over
traditional 1D modelling.
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Advanced 2D technique Traditional 2D modelling packages
greatly simplify the terrain HEC-RAS 2D technique retains the
terrain detail Cell face is a detailed cross-section
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Incorporation of Buildings Dense development should be
analyzed with buildings correctly represented
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Case Study
Guelph LakeGuelph Lake
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Case Study
characteristics description
hydrology
2-year flood: 106m3/s; 100-year flood: 256m3/sdam break peak flow: 7000m3/s
channel slope 0.003
channel width Average 53m
land cover sandy and gravelly soilchannel roughness 0.03
structures 11 bridges
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1D Model---(GRCA)
cross section property
number of XS 45
average spacing (m) 177
max spacing (m) 553
min spacing (m) 10
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2D Model Terrain Model Mesh Display
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2D Model--Terrain
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2D Model--channel
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2D Model—structures 11 bridges modeled as weirs
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2D Model—land cover
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Results 1D 2D
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Steady State Comparison 3 flow conditions Regional flood 100 year flood 2 year flood
1D framework—compare some points from both models 2D framework—generate maps of
depth deference
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Water Elevation Profile
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Depth difference 1D depth-2D depth
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Flooding Extents 1D and 2D flood boundary
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Conclusions Both 1D and 2D works well and easy to
set up 2D advantages: more stable, better
flood extents, good result resolution 2D limitation: Bridges can only be modelled as weirs for
high flows Velocity resolution is low Modelers should have good GIS
background Still need 1D channel data to modify
channel terrain area
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Acknowledgment Dr. Doug Joy, Ph.D., P.Eng Grand River Conservation Authority
(GRCA)—Gus Rungis
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Dam break hydrograph
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Dam break scenario
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Unsteady State