FMA 2D Challenge Models 2012

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1 Summary of the Participation in the 2D Modeling Challenges for 2012 Results of Challenge Models initially were presented at the 1 Day of 2D Symposium September 4, 2012 THOSE WHO PARTICIPATED IN PREPARING CHALLENGE MODEL SUBMITTALS: FIRM/AGENCY XP Solutions NCCHE / Ole Miss Wood Rodgers AECOM BMT WBM - TUFLOW DHI Innovyze Stantec CESI Hydronia FLO-2D Staff Involved Michael Crenshaw Jia Yafia, Yaoxin Zhang, Azad Hossain, Mustafa Altinakar, Yan Ding Shyamal Chowdhury, Mike Nowlan Joseph E Thomas, Andrew Shields, Sam Marginson Phillip Ryan, Bill Syme, Chris Nielson Josh Mendes, Dale Kerper Kedric Szana Mike Gerlach Thomas Plummer Reinaldo Garcia Jim O'Brien FMA appreciates the efforts of those individuals, companies and agencies that volunteered their time to prepare, execute and document their 2D models. THOSE WHO PARTICIPATED IN PREPARING THE CHALLENGE MODEL DATA, and PARTICIPATED IN TECHNICAL REVIEWS OF THE DATA IN ADVANCE OF THE DATA RELEASE: FIRM/AGENCY BAKER CESI City of Ventura DHI FEMA FMA HDR NV5 RBF Consulting (Baker) UC DAVIS West Consultants Staff Involved Patrick Clancey, Zhida Song- James Thomas S. Plummer Brian Trushinski Dale Kerper, Patrick Delaney, Bo Juza Kathleen Schaefer Iovanka Todt Mark Forest Wen Chen Pal Hegedus Bill Fleenor Marty Teal 1

Three Challenge Model Data Sets were issued in July of 2012.

2 Three Challenge Model Data Sets were issued in July of Each Challenge Model was setup to test different aspects of 2 D modeling, and the issues associated with deriving flood maps from the results of 2 D models. For each data set, the data provided was aliased to non real world coordinates in order to keep the data set anonymous. Challenge Model 1 Urban Riverine System: Challenge Model 1 represents an urban Riverine condition with an urbanized overbank floodplain. The model includes several hydraulic structures/bridges within the main stream system which will impact flood elevations. Flooding within the urbanized overbank floodplain is expected. The data provided for Challenge 1, included source data from a mixture of both Statute and Metric Units. The data was obtained directly from the documentation for the effective models submitted to FEMA. Data Provided: Model Boundary Terrain via 3D contours with a 2 ft interval (coarse terrain) Aerial Photograph Inflow Hydrographs at several points along the stream Supplemental Surveyed Cross Section Data Data on structure dimensions and locations Requested Deliverables: Shape file showing the maximum extent of flooding Depth grid showing maximum flood depths Outflow Hydrograph Maximum Flood Elevation Stream Profile The real location for Challenge Model 1 is Salvador Creek in the City of Napa. Two(2) Mesh based models and Ten(10) grid based models were submitted for this Challenge. Model Type Challenge 1 Flexible Mesh 0 Mesh (no 1D) 1 Mesh (1D Coupled) 1 TOTAL 2 (17%) Model Type Challenge 1 Grid (no 1D) 4 Grid (1D Coupled) 6 TOTAL 10 (83%) 2

3 Mesh Based Model Submittal Data for Challenge 1: Grid Based Model Submittal Data for Challenge 1: The effective floodplains mapped by FEMA are depicted in the following Depth Grid Image: 3

4 The diversity of maximum floodplain limit submittals that were received is shown in the following exhibits: MESH: GRID: 4

5 A comparison of the peak discharges from the Creek for each submittal is shown in the following table: Time at Maximum Flow Maximum Flow (cfs) 8:05 1,098 8:00 4,309 8:00 7,947 8:14 3,030 8:00 5,112 8:00 3,190 7:59 3,808 Critical Modeler Identified Issues affecting the Consistency of the Results were: Providing some items in Statute Units and some Items in Metric Units resulted in the mis interpretation of flows and dimensions by some of the modelers. Limitation of provided terrain data to 2 ft contours resulted in a number of issues associated with automated processing of the terrain into 2 D model domains. This resulted in some calculation differences between the modelers as well as flood mapping discrepancies with the effective submittal. Source information for the structure dimensions and locations was provided in the format from the original effective model. Some users had difficulty understanding this data. Both Uniform lateral inflows and single location inflows were specified. Not all software used had the ability to apply the uniform lateral inflow method. Limited time provided (available) to process the model data. 5

Challenge Model 2 Tidally Influenced Riverine and Coastal System: Challenge Model 2 represents a tidally influenced floodplain and riverine system along the California Coast.

The data was obtained directly from the documentation for the effective models submitted to FEMA.

6 Challenge Model 2 Tidally Influenced Riverine and Coastal System: Challenge Model 2 represents a tidally influenced floodplain and riverine system along the California Coast. The data provided for Challenge 2, included source data from a mixture of both Statute and Metric Units. There are no bridge structures within the model domain. The data was obtained directly from the documentation for the effective models submitted to FEMA. Data Provided: Model Boundary (included significant amount of Ocean area) Terrain via 5 meter Digital Elevation Model (DEM) Aerial Photograph Inflow Hydrograph for main Riverine and Tributary Ocean Tide Information coincident with hydrograph High water marks from Record Event data. Requested Deliverables: Shape file showing the maximum extent of flooding Table comparing results to the High Water Marks. The real location for Challenge Model 2 is the???. Five(5) Mesh based models and Eight(8) grid based models were submitted for this Challenge. Model Type Challenge 2 Flexible Mesh 2 Mesh (no 1D) 3 Mesh (1D Coupled) 0 Grid (no 1D) 6 Grid (1D Coupled) 2 TOTAL 13 6

diversity of maximum floodplain limit submittals that

7 Mesh Based Model Submittal Data for Challenge 2: Grid Based Model Submittal Data for Challenge 2: The diversity of maximum floodplain limit submittals that were received is shown in the following exhibits: MESH: 7

8 GRID: 8

Critical Modeler Identified Issues affecting the Consistency of the Results were: The lack of terrain data provided below the water surface in the main riverine complicated the ability of the

9 Critical Modeler Identified Issues affecting the Consistency of the Results were: The lack of terrain data provided below the water surface in the main riverine complicated the ability of the modelers to match the high water mark data. It was noted that the coarseness of the terrain data (5 meters) caused 2 high water marks to show their water elevations below the terrain elevation. It was noted that the terrain provided was different than the terrain in the 1960 s when the high water mark event occurred. This also complicated high water mark matching. Most of the modelers performed an iterative approach in their modeling, by adjusting n values to find a good match to the high water mark data. Most found that an n value of produced the best match, and those that made this assumption had very similar results, even though different software programs were used in the analysis. One submittal was provided using expected published n values, which resulted in a very large floodplain compared to the others, and this submittal did not match the high water mark data very well. Limited time provided (available) to process the model data limited the iteration process. 9

Challenge Model 3 Non Urban Riverine System: Challenge Model 3 represents a typical non urban stream of the California Central Valley, originating near the Sierra Nevada Foothills and conveying

10 Challenge Model 3 Non Urban Riverine System: Challenge Model 3 represents a typical non urban stream of the California Central Valley, originating near the Sierra Nevada Foothills and conveying runoff to the West into the Central Valley Flood Management System. These streams tend to be natural, with large amounts of conveyance in their upper reaches. As the streams progress downstream, their conveyance capacity gradually reduces. At some point nearing the valley floor, typically levees have been constructed to contain normal floods within the conveyance systems. The data provided for Challenge 1, included source data with only Statute Units. The data was obtained directly from preliminary information being used in the State of California s Central Valley Flood Evaluation and Delineation Program (CVFED). FEMA s LAMP, a new criteria for evaluating non accredited levee failure floodplains was offered to the modelers. They were told that the levees were to be assumed to be structurally stable even when overtopped. Overtopping flows were intended to occur. As a bonus, a modeling option was provided to evaluate potential transmission losses from infiltration. Data Provided: Model Boundary Terrain via LiDAR LAS files. Optional pre processed high resolution Gridded Regular Network (GMG format) based terrain files were also provided. Supplemental Survey Points and Breaklines. Bathymetry and wet survey Data. High Resolution Aerial Photograph Structure survey information and dimensions/locations. Inflow Hydrographs at upstream end of stream Land Use Data Soils Data Levee locations Requested Deliverables: Shape file showing the maximum extent of flooding Outflow Hydrograph Requested Deliverables for Bonus Scenario: Shape file showing the maximum extent of flooding Outflow Hydrograph 10

11 The real location for Challenge Model 3 is Ash Slough, a tributary to the Upper San Joaquin River. One(1) Mesh based models and Ten(4) grid based models were submitted for this Challenge, and for the Bonus Scenario Two(2) additional grid based models were also submitted. Model Type Challenge 3 Challenge 3+ Flexible Mesh 0 0 Mesh (no 1D) 1 0 Mesh (1D Coupled) 0 0 Grid (no 1D) 1 0 Grid (1D Coupled) 3 2 TOTAL 5 2 Mesh Based Model Submittal Data for Challenge 3: Grid Based Model Submittal Data for Challenge 3: Effective floodplains for this stream have not yet been mapped by the CVFED program. 11

12 The diversity of maximum floodplain limit submittals that were received is shown in the following exhibits: MESH: GRID: 12

GRID for the Bonus Models (with estimated transmission losses factored) Critical Modeler Identified Issues affecting the Consistency of the Results were: The provided terrain was cumbersome and

13 GRID for the Bonus Models (with estimated transmission losses factored) Critical Modeler Identified Issues affecting the Consistency of the Results were: The provided terrain was cumbersome and difficult for some modelers to manage and utilize to develop modeling domains with. Roughly 18GB of terrain data was provided. It was later noted that this is less than 2% of the terrain for one of the five modeling areas of the CVFED. There was difficulty interpreting the types of data points that were provided in the LAS files, and in one case some non terrain based data was included as terrain. Modeling area too large for pro bono efforts. Some of the Levee data included 3D elevations which did not match the terrain. Users were suggested to recomputed the levee elevations to match the terrain information. Limited time provided (available) to process the model data. 13

14 Overall Summary of Submittals Received by FMA: Model Type Challenge 1 Challenge 2 Challenge 3 Challenge 3+ TOTAL Flexible Mesh Mesh (no 1D) Mesh (1D Coupled) Grid (no 1D) Grid (1D Coupled) TOTAL Submitting Agencies D Software Vender s Applications Used Understanding the Nature of Challenge Models vs. Benchmarking: Benchmarking tests are constructed such that results can be compared to verified and known results for a controlled situation. They test the capability, accuracy and speed for each software program to solve the computational domain. We understand that the UK Environmental Agency is currently updating their Benchmarking study for 2 D and 3 D hydraulic analysis software. As they are currently preparing this analysis, FMA did not want to duplicate their efforts. The concept of the Challenge Model was developed to provide a means to deliver complex model sets to a group of modelers, wherein certain assumptions and derivations are necessary to be able to create a model domain, compute it, and convert those results into flood limits, elevations and flow rates. As opposed to just testing the software, in benchmarking, the Challenge Models test the joint efforts of the modeler and the software. This is closer to the real situation an agency such as FEMA is dealing with. This also opened the door for modelers other than software venders to volunteer their capabilities and talents to this effort. The 1 Day of 2 D symposium on September 4 th, 2012 dealt directly with trying to itemize and understand the variety of issues that can and have resulted in these situations. Examples from the Challenge Models were provided to those in attendance at this symposium and may be reviewed further in additional discussions of these issues. Lesson s Learned: Internal Technical Review of model data needs to be more thorough. Need to provide more time for models to be prepared Limit the items being tested in each model to help accelerate model creation time Provide more complete and uniform data sets to modelers There is a need to do more Challenges in the future 14

15 2 D models have an appetite for large amounts of data, which can contribute to a diversity of computational results via processing differences, but often it is also shown that it is the mere presence of having that data available during the flood mapping process that leads to highly complex flood maps with questionable details. What s Next: FEMA and UC Davis will be cooperatively assembling a Blue Ribbon Panel of experts to review issues associated with using 2 D models to prepare FEMA flood mapping products. Some suggested topics we have already received for potential future 2 D Challenge Models are: 2 D Integrated Hydrology Analysis. Urban Isolated Floodplains (combination storm drain and stream) Floodway Analysis LAMP Alluvial Analysis Sediment Transport and Mobile Bed Analysis Levee Breach Dam Breach Converting 2 D results directly to mapping (no modeling) If you have any additional suggestions or model ideas, please contact Thomas Plummer (thomas@civilsolutions.com) 15

Urban Floodplain modeling- Application of Two-Dimensional Analyses to Refine Results

Urban Floodplain modeling- Application of Two-Dimensional Analyses to Refine Results Prabharanjani Madduri, P.E., CFM Mathini Sreetharan, Ph.D., P.E., CFM Hydraulic modeling of urban areas and issues Modeling