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TRANSCRIPT
10/5/2015
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© 2015 HDR, Inc., all rights reserved.
Mitch Blum, HDR Engineering Inc.
The Coming Flood of 2D Models
1D Modeling
2D Modeling
Motivation for Advancement in Modeling
HEC-RAS 2D Modeling
“Flood” of 2D Models
Regulatory Implications
Outline
© 2015 HDR, Inc., all rights reserved.
1D Modeling Review
10/5/2015
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Steady State
Unsteady State
Cross Sections in ONE Direction
Hydraulic Computations in ONE Direction
Step Backwater
o Solves one direction
o Downstream to upstream
1D Modeling
1D Modeling
Advantages
o Simple cross sectional geometry
o Simple to run
o Faster computation time
o Hydraulic Structures
o Lots of supporting literature
Disadvantages
o Trouble modeling shallow overland flows
o Can overestimate depth and velocity due to 1D
assumptions
o Laying out cross sections difficult
o Requires engineering judgment
o Doesn’t capture complex dispersive flow
1D Modeling
Continuity Equation:Q A + = 0x t
2
o f
( /A)Q Q h gA( ) 0S St x x
α
Momentum Equation:
(Only in X direction)
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© 2015 HDR, Inc., all rights reserved.
2D Modeling Review
Uniform Grid – Square cells
Rectilinear Grid – Rectangular cells
Unstructured Grid/Mesh
o Triangles
o Quadrilaterals
o Polygons
2D Model Construction
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Always Unsteady state
Hydraulic computations in 2 Directions, X
and Y
Solves Full St. Venant Equations
o X and Y
2D Modeling
2D Modeling
2D Modeling
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Advantageso Simple overland model construction
o Dispersive shallow flow
o No guessing at cross section orientations
o More informative dynamic mapping
o Modeling in 2 directions
Disadvantages• More data intensive to build
• Limited on hydraulic structures
• Heavy reliance on terrain quality
• Computational time and power
• Expensive (commercial)
2D Modeling
Integrated 1D/2D Modeling
Images courtesy of XP Solutions
Integrated 1D/2D Modeling
Images courtesy of City of Fort Worth
Using 1D Model Only
Using 1D-2D
Combined Model
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Complex Unknown Flow
50 Lateral Structures
3 Reaches
Stability Issues
1D Tanana Model
© 2015 HDR, Inc., all rights reserved.
Motivation for Advancement in Modeling
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“Post Katrina World”
Katrina
o Post Katrina Emergency Management Reform
Act 2006
o Tighter Regulations
o More emphasis on analysis
Extreme Publicized Events
Source: NOAA
Brett Duke / The Times-Picayune
Dam Breach
o Teton Dam Breach
o Bastrop Example
o Statewide Requirements
o Emergency Management Plans
Levee Breach
Early Warning Systems
o Mississippi USACE Breach
Extreme Publicized Events
Engineering Channel
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Mississippi
Ohio River
Flooding 2011
Forced Levee
Breach
Installed over
100 Temporary
Gages to
Capture the
Event
Used as Model
Validation
Faster Computational Time for Emergency Response Modeling
Source: HEC
© 2015 HDR, Inc., all rights reserved.
HEC-RAS 5.0
Alpha Version 1 – April 2013
Alpha Version 2 – Aug 2013
Beta Version – May 2014
Revised Beta – June 2014
Revised Beta – Oct 2014
Revised Beta – March 2015
Revised Beta - August 205
5.0 Release – September 2015
Timeframe
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1D/2D Integrated Hydrodynamic Model
Regular or Irregular 2D Grid Cells
Finite Volume Solution
Full Saint Venant or Diffusion Wave
Equation Solution Options
Unstructured or Structured
Computational Meshes
Detailed Hydraulic Table Properties for
Computational Cells and Cell Faces
RAS Mapper
HEC-RAS 5.0
Public Domain
Extensively Tested
Computationally Efficient
Terrain Processing
New Codeso Not repackaging existing codes
Unique Approach to 2D Solutiono Sub grid cell detail
How is it Different?
Computational Mesh with Sub-Grid
Terrain Data (Terrain Detail is Utilized)
Each Cell Face is a Detailed Cross
Section
Gridding Pre-Processing Defines
Hydraulic Property Lookup Tableso Elev-Wetted Perimeter (Face)
o Elev-Area (Face)
o Roughness (Face)
o Elev-Volume (Cell)
Model Uses Tables During Run (Faster)
How is it Different?
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Finite
Volume
1D*
1D*
1D*
1D*
*HEC-RAS 2D accounts for irregular skew in grid cell face
Source: HEC
HEC-RAS 5.0
Terrain Creation and Association
Multiple Terrain Support
o Hierarchical control
Flexible Tile – Resolutions
Less terrain file size limits
Map Projection
o Reference or manual assign
Shapefile backgrounds
Web Imagery
RAS Mapper
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Static and Dynamic Results
o Depth
o Water Surface Elevation
o Velocity
o Inundation Boundary
o Flow (1D only)
o Depth * Velocity
o Arrival Time
o Recession
o Duration
o Percent Time Inundated
Web Imagery
Shapefiles
Profiles
HEC-RAS Visualization
Visualization
© 2015 HDR, Inc., all rights reserved.
The “Flood” of 2D Models
Matt Cardy/Getty Images
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Cost
Computational Power
Reliance on GIS or CAD systems
FEMA Acceptability
Historic Impediments to the “Flood”
Hydro Response Ltd
Getty Images
© 2015 HDR, Inc., all rights reserved.
Breaking Down the Barriers
HEC-RAS 5.0
o Free to download, install, and
use
o Upwardly compatible
o Free documentation
o Ongoing support
Proprietary Software
o Upward of $60,000
Cost
Lori SR
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64 Bit Computations
Multiple Processors
Faster Processors
Solid State Memory
Video Graphic Cards
Shorter Runtimes
Larger Storage Available for Output
Advances in Computer Hardware and Software
HEC-RAS Moving
Away from GIS
Geospatial Processing
within HEC-RAS
o Pre-processing Model
geometry
o Terrain development
and modification
o Modeling output and
visualization
Reliance on GIS or CAD
© 2015 HDR, Inc., all rights reserved.
Regulatory Implications
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PROGRAM DEVELOPED BY AVAILABLE FROM COMMENTS
FESWMS 2DH
1.1 and up
(Jun. 1995)
U.S. Geological Survey
U.S. Geological Survey
National Center
12201 Sunrise Valley Drive
Reston, VA 22092
USGS.gov/
For sediment transport.
FLO-2D
v. 2007.06 and 2009.06Jimmy S. O'Brien
FLO-2D Software, Inc.
P.O. Box 66
Nutrioso, AZ 85932
FLO-2d.com/
Hydrodynamic model that has
the capabilities of modeling
unconfined flows, complex
channels, sediment transport,
and mud and debris flows.
MIKE Flood HD
v.2009 SP4DHI Water and Environment
DHI, Inc.
319 SW Washington St.
Suite 614
Portland, OR 97204
A coupling of MIKE 11 (one-
dimensional) and MIKE 21 (two-
dimensional) models. Solves the
fully dynamic equations of
motion for one- and two-
dimensional flow in open
channels, riverine flood plains,
alluvial fans and in costal zones.
TABS RMA2
v. 4.3 and up (Oct. 1996)
RMA4
v. 4.5 and up (July 2000)
US Army Corps of Engineers
(USACE)
Coastal Engineering Research
Center
Department of the Army
Waterways Experiment Station
Corps of Engineers
3909 Halls Ferry Road
Vicksburg, MS 39180-6199
Limitations on split flows.
Floodway concept formulation
unavailable. More review
anticipated for treatment of
structures.
XP-SWMM 2D/XPStorm 2D
v. 12.00
(May 2010)
XP Solutions
XP Solutions
5415 SW Westgate Dr.
Suite 150
Portland, OR 97221
XPSolutions.com
Simulates two-dimensional free
surface flows by solving the full-
dimensional, depth averaged,
momentum and continuity
equations. Dynamically linked
with the one-dimensional
modeling of XP-SWMM/XP-
Storm.
Current FEMA Accepted 2D Models
Approved FEMA Model List
o HEC-RAS automatically approved upon
release
o Extensive validation process
Applicability of Use
o Justification to FEMA to use 2D
o Is the Effective Model adequate?
Floodway Challenges
o Method 4 not available
o Method 1 not available
o Use of terrain to block encroachments
Model Review
o Challenge to find experienced reviewers
Regulatory Implications
Education
o Understanding how the model works
o Training staff
o “How to Review a 2D Model”
Anticipate and Plan
o What communities are appropriate for 2D?
o Emergency response
Reach out to others
• Communities
• Experts
• Regulators
2D Model “Flood” Preparedness
Creative Commons
Michael Yamashita