HEC-RAS in Three Dimensions

Now this is the kind of post that gets you on The RAS Solution!  Cutting edge creative solutions to complex problems.  This is great stuff.  Thanks Michael for all the effort you put in to this.

Written by Michael Link | AECOM

Copyright © The RAS Solution.  All rights reserved.  

In today’s post we’ll cover two methodologies that leverage HEC RAS results to create impressionable and multi-dimensional flood visualizations. If these methodologies are implemented industry-wide, it is likely that the public will become more engaged with our work and our clients wowed. Products of the two methods are shown below.

Figure 1: 3DV-Flo Output of Muncie, Indiana (left) and 3D Printed Flood of Puerto Rico (right)

Introduction

The mitigation of flood risk is traditionally accomplished through regulation, correct science, and public buy-in. The federal government writes the regulation, we make the floodplain maps, and homeowners begrudgingly purchase flood insurance. How can we as engineers change the public’s sentiment towards our work and how can we further reduce infrastructure damage? One way we can do this is by transforming HEC RAS results into a format that is visually stimulating and easily digestible for nearly anyone. 

FIRM maps, WSEL/Depth rasters, and inundation boundaries serve the purpose of communicating information but do not necessarily communicate flood risk in a simple and powerful manner. This post is targeted at transforming RAS results into just that, a simple and powerful resource for capturing the attention of the public. If flood risk is internalized by communities, we can expect infrastructure loss to decrease and funding for our line of work to increase. Let’s dive in!

3DV-Flo (3D Visualization of Flooding)

3DV-Flo is a methodology that takes in RAS results and generates a 3D flood visualization in Google Earth. Here are a few examples of 3DV-Flo output.

Figure 2: Austin, Texas flooding visualized with 3DV-Flo

Figure 3: Google Street View of 3DV-Flo output

Figure 4: Muncie, Indiana flooding visualized with 3DV-Flo

The following YouTube playlist shows examples of 3DV-Flo output (the first video in the playlist is embedded below).  If you would like to explore the output yourself in Google Earth, the non-regulatory KML’s can be downloaded here.

3DV-Flo allows the information stored in WSEL and depth rasters to be viewed three-dimensionally in Google Earth. This output is an improvement upon RAS Mapper generated KML’s in that the results are no longer clamped to the ground. The 3DV-Flo method relies on three inputs (an inundation boundary, depth raster, WSEL raster), two free software (HEC-RAS, Google Earth), and one proprietary software (ESRI ArcGIS*). The 3DV-Flo toolbox has been tested on ArcMap for Desktop versions 10.3.1 and 10.6.1. Compatibility of this toolbox cannot be guaranteed with ArcGIS Pro or other Desktop versions. Additionally, there are two model types within the 3DV-toolbox. The first uses tools from the Advanced ArcGIS License. The advanced model is slightly faster and provides the functionality of adding breaklines to your resulting mesh. Breaklines are helpful for modelling levees, elevated roads, and dams. The second model uses tools solely from the Basic ArcGIS license, but you must have the 3D Analyst and Spatial Analyst extensions activated as described in this ESRI post. If this tool has a red ‘X’ next to it in ArcGIS follow the steps discussed in this video.  Lastly, if you are using the basic version of the 3DV-Flo toolbox it is essential that your inundation boundary shapefile name not contain spaces or special characters.  For example, if your shapefile name is Inundation Boundary (Max Value_0).shp, you should modify this to be InundationBoundaryMaxValue,shp before using the toolbox.

Assuming you have a georeferenced 1D or 2D RAS model and access to ArcGIS, let us proceed with the tutorial. You can follow along with the video below or you can scan the detailed written instructions.

*3DV-Flo methods are currently dependent on ESRI ArcGIS. These methods can surely be recreated in QGIS or in a standalone script given enough time and ingenuity. Any individual with the time and desire to make this a fully open-source method can reach out to Michael Link for further guidance. 

3DV-Flo (3D Visualization of Flooding) Steps:

                  1.  Download 3DV-Flo Files

a.       Download 3DV-Flo zipped files from Github here

                  2.  Within HEC RAS

a.       Open geo-referenced HEC RAS project

b.       Open RAS Mapper

c.       Import best available terrain if not already there

d.       Right-click results and click ‘Add new results layer’ for the max inundation boundary, depth raster, and WSEL raster

e.       Compute/update layers

f.        Export break lines as shapefile if applicable

                  3.  Within ArcGIS

a.       Open blank MXD

b.       Import model output (inundation boundary, depth raster, WSEL raster, and breaklines) to MXD

c.       Import symbology shapefile. Adjust symbology to be blue with no border and displayed with a transparency of 40%

d.       Open the 3DV-Flo toolbox by navigating there in ArcCatalog

e.       Open the 3DV-Flo_WSEL tool

                                                               i.      The 3DV-Flo_Depth tool is used to reference flood depths to the ground rather than to mean sea level. This tool can be used when the vertical datums between RAS and Google Earth differ.

                                                             ii.      To use this tool right click the KML in Google Earth, click properties, click altitude, and switch the altitude to be ‘relative to ground’

f.        Populate tool parameters and specify where the Google Earth KMZ is to be saved

g.       If breaklines are not applicable, then bring in the ‘Arbitrary_Breakline’ shapefile from the unzipped folder

h.       Run 3DV-Flo tool

                 4A - Within Google Earth for Desktop

a.       Download software here if not installed on your machine

b.       Open Google Earth

c.       Click File>Import>and then navigate to the KMZ you created in ArcGIS

                 4B - Within Google Earth for Chrome

a.       Open Google Earth in chrome browser

                                                               i.      https://Earth.Google.com/web/

b.       Click three horizontal lines in the top left of window

c.       Click my places

d.       Click import KML file

e.       Click open file

f.        Navigate to KML file of interest and import

There are two known 3DV-Flo ‘bugs’. The first of which deals with poor terrains spatially restricting results. The second deals with 3DV-Flo output that appears unrealistically high in Google Earth. The first bug can be fixed by updating the underlying terrain. The second bug can be fixed by relating 3DV-Flo output relative to the ground rather than to mean sea level. These bugs and their respective workarounds are discussed in this video.

The vision for 3DV-Flo in the future includes 1. widespread adoption of the method by industry, 2. conversion of the entire US regulatory floodplain into 3DV-Flo format, and 3. the combination of 3DV-Flo with the National Water Model forecasts to help cities prepare for incoming floods. Advancing goal #1 is in part achieved through the readership of this post. Advancing goal #2 is theoretically possible by splitting the NFHL polygon layer nationwide by all XS’s with regulatory elevations. The resulting polygons could be transformed into 3DV-Flo output. Lastly, goal #3 has been prototyped in this video and this post. Any assistance to advance these goals is welcomed.

3D Printed Floods

According to the Wohlers Report 2019, the 2020 value of 3D Printing and Additive Manufacturing will be $15.8 billion! Can we get a piece of that??? One way that we can participate in this trend is to overlay RAS results onto 3D printed terrains. Here is a YouTube playlist link to some examples of just that for a pluvial flooding model of Puerto Rico (the first video in the playlist is embedded below).

The intended effect of this visualization is to intuitively convey how floods develop and where they pose the largest threat. 3D printed terrains are often presented at a large scale due to the coarse nature of the underlying digital elevation model. This visualization is unlikely to be used as a structure by structure evaluation of risk. It is more likely to be used in a city hall meeting or in the classroom. The Austin, Texas Watershed Concepts Group from AECOM was the first (to my knowledge) to prototype a 3D Printed Flood. Details on their FEMA funded San Marcos, Texas project can be found here. That same group generated a second 3D printed flood for Puerto Rico to give locals a high-level understanding of, go figure, watershed concepts. The projector and mount costed roughly $500. The San Marcos 3D print costed $1400 and the Puerto Rican model $250. The difference in price was related to print infill density and size.

If you are interested in making one of these models you can follow along with the video tutorial below and/or you can scan the detailed written instructions.

3D Printed Flood Steps:

                  1.  Develop 3D Printed Terrain

a.       Check 3D model repository (Thingiverse or Google searching 3D printed terrain of “Location”) to see if your location already has an STL 3D print file

b.       If there is no pre-existing STL file or you would like to make your own, you have a few options. 

                                                               i.      Create STL from the Terrain2STL (Ideal due to time saved and nonideal due to fixed rectangular shape of STL)

                                                             ii.      Create terrain from Touch Terrain (Ideal due to time saved and ability to specify bounding coordinates)

                                                           iii.      Create STL by converting Lidar to greyscale image (process described here) and load into Blender to convert the greyscale into an STL file (process described here).

                                                           iv.      More options detailed here.

c.       Modify STL file as needed in Meshmixer

                                                               i.      The most important functions in Meshmixer are:

1.       Edit > Plane Cut – This function allows you to discard unnecessary pieces of your model and to break your model down into smaller chunks to be printed by small 3D printers

2.       Edit > Transform – This function allows you to stretch your model solely in the Z direction. For more hash marks click the up arrow.

3.       Analysis > Units/Dimensions – This function allows you to rescale your model proportionally in all directions

d.       If you do not have a 3D printer at home or in the office, shop around to see where you can get the best deal. For prototyping, I found that 3D Hubs was the cheapest and easiest to use. Their banana reference was amusing and useful for catching extremely large or small prints. For the final 1.5-foot-long print of Puerto Rico, I used a local printing service so that I could guarantee the quality and interact with a human. Here is a list of the top 10 online 3D printing services in 2019.

                  2.  Develop Movie of Flooding in HEC RAS

a.       Download ShareX or comparable screen capture software

b.       Create or load a pluvial or fluvial model in HEC RAS

c.       Open RAS Mapper

d.       Load web imagery, terrain, or basemap to be displayed in movie

e.       Open ShareX and create screen capture video of unsteady RAS simulation

3.  Project Movie of Flooding onto 3D Printed Terrain

a.       Download VLC media player or comparable video software

b.       Open the flooding movie in VLC

c.       Connect the computer to projector via HDMI cable

d.       Setup a projector and table mount

e.       Pause flooding movie at peak flooding and calibrate the movie extent to 3D print extent by

                                                               i.      Raising or lowering the Pixar lamp stand

                                                             ii.      Adjust the aspect ratio of video

f.        Equipment setup is detailed further in this video

g.       Project flooding onto terrain with basemap

In Conclusion

As illustrated in this post, the impact of our RAS modeling can be greatly bolstered with spectacular Google Earth imagery and mesmerizing 3D prints. By presenting our clients and communities with these flood visualization resources, our work can be used outside of the narrow confines of designating whether someone should or should not buy flood insurance. 

Acknowledgements

The inspiration for the 3DV-Flo methodology would not have been possible without the catalysts listed below.

1.       a Scottish scientist’s Google Earth clamped-to-ground flood simulation

2.       a breakline/polygon GIS tool from Ryan Dalton

3.       a sea-level rise Google Earth tutorial from David Sadoff

4.       and a Google Earth flood simulation from Mariusz Krukay

Much gratitude goes out to Muhammad Ashraf and Yuxiang Kang for technical guidance and edits, Alyssa Ruiz for computational fine-tuning, John Wade for wise GIS counsel, Yacoub Raheem, Clint Kimball, and Justin Baker for patient 2D HEC-RAS Training, and Chris Wright for overall mentorship. A big thanks goes out to the U.S. Government for providing industry-standard software and innovations free of charge to the world through funding of top-notch institutions (Hydraulic Engineering Center, National Laboratories, Academia, etc.) and openly sharing findings. Lastly, I'd like to thank Chris Goodell for this platform and for single-handedly progressing and pushing the hydraulics industry forward over the past decade. Your clear explanations and innovative posts have been the cornerstone of my understanding of HEC-RAS.

Contact Details:

For more information on this topic, please message Michael Link through LinkedIn - https://www.linkedin.com/in/michael-link-b88329118/

Michael Link works for AECOM in Austin, Texas.  He received a B.S. in Ecological Engineering from Oregon State University and an M.S. in Environmental and Water Resources Engineering from The University of Texas at Austin.  Michael is an EIT and certified floodplain manager.  Outside of work,  enjoys combining hydraulics, spatial analysis, and data science in novel ways.