10/5/2015. The Coming Flood of 2D Models. 1D Modeling Review

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1 The Coming Flood of 2D Models Mitch Blum, HDR Engineering Inc. Outline 1D Modeling 2D Modeling Motivation for Advancement in Modeling HEC-RAS 2D Modeling Flood of 2D Models Regulatory Implications 1D Modeling Review 1

1D Modeling Steady State Unsteady State Cross Sections in ONE Direction Hydraulic Computations in ONE Direction Step Backwater o Solves one direction o Downstream to

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

2 1D Modeling 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 Continuity Equation: Q + A= 0 x t (Only in X direction) Momentum Equation: 2 Q ( αq /A) ga( h S ) 0 o S f t x x 2

3 2D Modeling Review 2D Model Construction Uniform Grid Square cells Rectilinear Grid Rectangular cells Unstructured Grid/Mesh o Triangles o Quadrilaterals o Polygons 3

4 2D Modeling Always Unsteady state Hydraulic computations in 2 Directions, X and Y Solves Full St. Venant Equations o X and Y 2D Modeling 2D Modeling 4

2D Modeling Advantages o 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

5 2D Modeling Advantages o 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) Integrated 1D/2D Modeling Images courtesy of XP Solutions Integrated 1D/2D Modeling Using 1D Model Only Using 1D-2D Combined Model Images courtesy of City of Fort Worth 5

6 1D Tanana Model Complex Unknown Flow 50 Lateral Structures 3 Reaches Stability Issues Motivation for Advancement in Modeling 6

7 Extreme Publicized Events Post Katrina World Katrina o Post Katrina Emergency Management Reform Act 2006 o Tighter Regulations o More emphasis on analysis Source: NOAA Brett Duke / The Times-Picayune Extreme Publicized Events 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 Engineering Channel 7

8 Faster Computational Time for Emergency Response Modeling Mississippi Ohio River Flooding 2011 Forced Levee Breach Installed over 100 Temporary Gages to Capture the Event Used as Model Validation Source: HEC HEC-RAS 5.0 Timeframe 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 Release September

9 HEC-RAS 5.0 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 How is it Different? Public Domain Extensively Tested Computationally Efficient Terrain Processing New Codes o Not repackaging existing codes Unique Approach to 2D Solution o 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 Tables o Elev-Wetted Perimeter (Face) o Elev-Area (Face) o Roughness (Face) o Elev-Volume (Cell) Model Uses Tables During Run (Faster) 9

0 Source: HEC RAS Mapper Terrain Creation and Association Multiple Terrain Support o

10 1D* 1D* Finite Volume 1D* 1D* *HEC-RAS 2D accounts for irregular skew in grid cell face HEC-RAS 5.0 Source: HEC RAS Mapper 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 10

HEC-RAS Visualization Static and Dynamic Results o Depth o Water Surface Elevation o Velocity o Inundation Boundary o Flow (1D only) o Depth * Velocity o

11 HEC-RAS Visualization 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 Visualization The Flood of 2D Models Matt Cardy/Getty Images 11

12 Historic Impediments to the Flood Cost Computational Power Reliance on GIS or CAD systems FEMA Acceptability Getty Images Hydro Response Ltd Breaking Down the Barriers Cost 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 Lori SR 12

13 Advances in Computer Hardware and Software 64 Bit Computations Multiple Processors Faster Processors Solid State Memory Video Graphic Cards Shorter Runtimes Larger Storage Available for Output Reliance on GIS or CAD 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 Regulatory Implications 13

14 Current FEMA Accepted 2D Models PROGRAM DEVELOPED BY AVAILABLE FROM COMMENTS FESWMS 2DH 1.1 and up (Jun. 1995) U.S. Geological Survey U.S. Geological Survey National Center Sunrise Valley Drive Reston, VA USGS.gov/ For sediment transport. FLO-2D Software, Inc. Hydrodynamic model that has P.O. Box 66 the capabilities of modeling FLO-2D Jimmy S. O'Brien Nutrioso, AZ unconfined flows, complex v and channels, sediment transport, FLO-2d.com/ and mud and debris flows. A coupling of MIKE 11 (onedimensional) and MIKE 21 (twodimensional) models. Solves the DHI, Inc. MIKE Flood HD 319 SW Washington St. fully dynamic equations of DHI Water and Environment v.2009 SP4 Suite 614 motion for one- and twodimensional flow in open Portland, OR channels, riverine flood plains, alluvial fans and in costal zones. Coastal Engineering Research TABS RMA2 Center Limitations on split flows. v. 4.3 and up (Oct. 1996) Department of the Army Floodway concept formulation US Army Corps of Engineers Waterways Experiment Station unavailable. More review (USACE) RMA4 Corps of Engineers anticipated for treatment of v. 4.5 and up (July 2000) 3909 Halls Ferry Road structures. Vicksburg, MS Simulates two-dimensional free XP Solutions surface flows by solving the fulldimensional, depth averaged, 5415 SW Westgate Dr. XP-SWMM 2D/XPStorm 2D Suite 150 momentum and continuity v XP Solutions Portland, OR equations. Dynamically linked (May 2010) with the one-dimensional XPSolutions.com modeling of XP-SWMM/XP- Regulatory Implications 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 2D Model Flood Preparedness 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 Creative Commons Michael Yamashita 14

2D Modeling of Urban Flood Vulnerable Areas

2D Modeling of Urban Flood Vulnerable Areas Sameer Dhalla, P.Eng. Dilnesaw Chekol, Ph.D. A.D. Latornell Conservation Symposium November 22, 2013 Outline 1. Toronto and Region 2. Evolution of Flood Management