Monday, May 14, 2018

Closing the wormhole with the new features in HEC-RAS 5.0.4!

Written by Krey Price  |  Surface Water Solutions
Copyright © The RAS Solution 2018.  All rights reserved

The Great Hobbiton Flood

For those who have used wormhole culverts or mega-cell culverts in previous versions of HEC-RAS, you'll be relieved to hear that they have officially been retired with the May 2 release of the new Version 5.0.4.

It sounds like the new features are already getting lots of use, and online and face-to-face training courses are popping up all over the world. Given the surge in interest, we thought we'd post a quick overview of the new features and compare some model results between versions. We've found, for example, that the new coordinate-based culvert features in Version 5.0.4 give identical results to wormhole culverts in Version 5.0.3, with both methods drawing flow from the 2D cells that cover the actual inlet location:

[Left-click to play, then right-click on the video to loop the particle tracing - a handy trick to keep file sizes small while providing a continuous animation in a presentation!]

This article highlights the new culvert capabilities along with the following features, each of which is also covered in an accompanying instructional video here:
  • Culverts. We’ll see how the new culvert editor gets rid of the need for wormhole culverts (RIP!) by allowing the inlet and outlet of each barrel to be defined by its own set of coordinates.
  • Mesh Polygons. We’ll then add a “Refinement Region” to a 2D Flow Area using the new RAS Mapper tool that allows you to assign customized computational grid spacing with polygon features.
  • Internal Boundary Conditions. Next we’ll add inflow hydrographs inside of the 2D Flow Area as internal boundary conditions.
  • Adjustable Time Steps. We’ll set Courant Number criteria to allow variable time steps to be selected based on computed velocities.
  • Rating Curves. We’ll then run the model and generate rating curves in a single step (rather than having to extract flow and stage time series hydrographs separately and combine them in Excel).
  • Speed Enhancements. Finally we’ll compare run times to see how the speed improvements stack up.
This demonstration model uses terrain data covering the Hobbit movie set in New Zealand. You can download the terrain for free if you want to follow along (instructions for setting up the project with saved views and static aerial imagery are available here.)

If a HEC-RAS model contained wormhole culverts in Version 5.0.3, they will be ignored when the project is opened in Version 5.0.4, so we’ll need to convert any wormhole culverts to “coordi-culverts”, with coordinates assigned to each barrel’s inlet and outlet either manually or with a great new feature to import culvert centerlines from a shape file:

Here’s the schematic plan view for four culvert methods available in Version 5.0.4, with the new “coordivert” in our demonstration model shown in the canal on the far right:
A description of each method is included here. (A fifth method, entering the bridge piers or culvert walls as 2D terrain only, wasn't included here since it is only appropriate for open channel flow.)

Mesh Polygons
To take advantage of the new capability to define a finer mesh within a polygon, we'll use a "Refinement Region" in RAS Mapper. After delineating a polygon under the refinement regions layer, the next step is to right-click on the shape and select “Edit Refinement Region Properties” and enter a cell spacing (in this case 1 meter by 1 meter):
With the higher resolution area defined, if you zoom in on the refinement region, you’ll see a more detailed computational mesh inside the 2D Flow Area:
In this case, I've defined a tighter mesh spacing around the roadway and culvert and left a lower-resolution mesh in the open channel areas. This feature can save a substantial amount of computation time and prevents the need to create multiple 2D areas to reflect varying resolution requirements – or the menial task of creating an excessive number of snaking breaklines with red-dot errors that need fixing!
Internal Boundary Conditions
In Version 5.0.4, BC lines can now be entered as internal boundary conditions inside the 2D Flow Area. Keep in mind that flow will be able to travel in both directions from an internal BC Line, and any BC line in 5.0.3 that crossed the external boundary of the 2D Flow Area will need to be edited to be either all in or all out. At this point flow can only be positive (can’t subtract flow to represent infiltration or a stormwater pit) but with Version 5.0.4 there isn’t any need to use the wormhole culvert hack to move flow around your 2D area anymore. To test it out, we’ve moved the BC lines inside of the upstream boundary, and the model behaved just fine:

Adjustable Time Step
The window with the new option to use the Courant Number criterion is shown below. With the adjusted time step selected, the model will increase or decrease the computational time step automatically based on the computed velocity. This can give you significant speed improvements if you were already conservative with your time step. If you had an unstable model, however, the use of this feature will slow it down as it slices the time step to stabilize it. In this case, our 0.5-second time step can be doubled four times or halved four times, giving it a potential range from 0.03 to 8 seconds:

Rating Curves
One last feature we’ll illustrate is the ability to plot rating curves directly along any saved profile line with a single command. Just right-click on your saved profile line name and select “Rating Curve” as a new option under Time Series (but watch out for the potential pitfalls mentioned in the article here!). Here’s where to find the rating curve function in RAS Mapper:

Speed Comparison
Using the same grid size and time step, this particular model runs twice as fast in 5.0.4 as it did in Version 5.0.3. Taking advantage of the refinement areas and variable time steps, it runs even faster - in less than a quarter of the 5.0.3 time without any significant loss of accuracy. We’ve seen similar speed enhancements with our other models as well.
Comparing results
In this particular demonstration model, the water surface elevation profile results in 5.0.4 look nearly identical to the results from 5.0.3. Here is the particle tracing with the coordi-culvert in 5.0.4 shown at the right-hand side of the image. This one matches the particle tracing in Version 5.0.3 using a wormhole culvert in place of the coordi-vert:
Here are the water surface profiles comparing the coordi-culvert to the wormhole culvert for open channel flow, pressure flow, and overtopping flow conditions:
As you can see, in the vicinity of the culvert, the results are effectively identical for all three flow conditions, which brings us to the bottom line: the wormhole has closed with the release of Version 5.0.4, and wormhole culverts have officially been retired – not just for long culverts, but for internal boundary conditions as well. Mega-cell culverts have also become obsolete now. From what we’ve seen so far, the new culverts provide equivalent results with much more functionality - particularly the fact that they work perfectly fine with the roadway/bridge deck represented as terrain or removed from the terrain and replaced with a weir embankment - so good riddance to both the worms and the Cells Of Unusual Size!
And finally just for fun, let’s ramp up the flow and see if an Orc-dam can flood out Hobbiton; if you want to see how the Hobbits fare in the flood, further details, animations, and comparisons of the new features are available here, or feel free to follow along with the instructional videos covering each of these new features separately.

In this case, our particle tracing shows that this one may catch Frodo in a whirlpool - and suck him right through the Orc-pipe that we can now move anywhere in our model thanks to the new coordiverts in Version 5.0.4!
[Again, right-click to loop]

We'd love to have you join us in an upcoming comprehensive training course, but in the meantime, we hope this has been a helpful overview of some of the new features in 5.0.4! We look forward to hearing how you are using the new features in your own projects.
Krey Price
Surface Water Solutions

Monday, May 7, 2018

6th HEC-RAS Water Modelling 1D+2D Course in Sydney, Australia

If you're in the neighborhood, or just want a nice trip to Australia, consider taking this excellent course in 1D/2D Modelling using HEC-RAS the week of 4 June, 2018, hosted by ICEWaRM and the Australian Water School.  This will be a great opportunity to get some training on the new features just introduced in the recently released version 5.0.4. 

Click here for more information and to register.

Latest version! Hydrologic Engineering Centres-River Analysis System (HEC-RAS)

HEC-RAS is recognised globally as an industry standard hydraulic modelling program and is available for use without charge. Using the latest version, these courses cover basic, intermediate and advanced levels across both 1D and 2D, and gives you access to select HEC-RAS experts who are BETA testers and work in the industry.

You can choose from 3 options in this HEC-RAS training:
2-day (Mon-Tues) 1D only
3-day (Wed-Fri) 2D only
5-day (Mon-Fri) 1D + 2D
Note: The 2D course assumes a basic understanding of 1D.

HEC-RAS 5.0.4 contains many key new features for editing both 1D and 2D data sets, much faster computations, the new 64 bit RAS Mapper can handle much larger terrain data sets and there are improvements to the solution for some settings. HEC GEO-RAS and other third party utilities are no longer needed to create 1D model elements! Come learn these new HEC-RAS features in this combined 1D and 2D training opportunity.
Date: Monday, 4 June, 2018 - Friday, 8 June, 2018
Location: SYDNEY: Novotel Sydney on Darling Harbour

Contact: Trevor Pillar:

Saturday, May 5, 2018

Important follow-up on 5.0.4

If anyone downloaded and installed HEC-RAS 5.0.4 before Friday May 4th at 4:00 PM pacific daylight time, please re-download and install the software.  There were some minor mistakes found in the original 5.0.4 release.

Please click here to find the download links for all of the updates:

Thursday, May 3, 2018

HEC-RAS 5.0.4 is released!

Message from HEC on the new release of HEC-RAS version 5.0.4.  Make sure to also check on the new Verification/Validation and the Benchmarking documents. 

***Note.  If you originally downloaded 5.0.4 before May 4 at 4:00 pm PDT then please redownload and install from the links below.  There were some minor errors found in the original release.

Download HEC-RAS Version 5.0.4 here:

Download RD-52  HEC-RAS Verification and Validation Tests document here: 

Download RD-51 Benchmarking of the HEC-RAS Two-Dimensional Hydraulic Modeling Capabilities here:

There are several other new useful documents related to HEC-RAS here:

From HEC:
We have released the final version of HEC-RAS 5.0.4 today.  It is now available for download from our webpage at the link below.  I have enclosed the 5.0.4 release notes for your review.  I have also included a separate document that describes how to use the new features contained in this version. Additionally  I have also included a document on how to spec out a computer for doing 2D modeling with HEC-RAS.

            We hope you enjoy the new version of the software.  As always, please keep us informed on any bugs you find, or your ideas for new features.  Here is the link to the HEC-RAS 5.0.4 web page:

            The following is a list of the major new features you can read about in the Release Notes and the Supplemental User’s Manual:

  1. New RAS Mapper Pre-Processor Tools
  2. Variable Time Step Capabilities (improved accuracy and faster run times)
  3. Increased Computational Speed for 2D Computations (2 to 5 times faster run times)
  4. Enhancements to SA/2D Hydraulic Connections
  5. New 2D Polygon Mesh Refinement Tool
  6. Internal Boundary Condition Lines for 2D Areas
  7. New Velocity Term for 2D Flow Area Boundary Conditions
  8. 64–bit Version of RAS Mapper and 64-bit 2D Pre-Processor (RAS now can handle much larger 2D models)
  9. Improved Terrain Generation Utility
  10. Improved Manning’s n Layer Development
  11. Sediment – New Options in the User Defined Grain Class Editor
  12. Sediment – New Transport Function Calibration Options

WARNING: Some of the bug fixes “may” cause the computed results from 5.0.3 to 5.0.4 to change.  Please read the Release Notes carefully for information about these changes.

There are two new verification and validation documents for HEC-RAS now available on our web page in the HEC-RAS area.  Here is a short description of each:

  1. RD-52  HEC-RAS Verification and Validation Tests (Enclosed in this email)

            This is the first ever full blown Verification and Validation document for HEC-RAS.  In this report we compare HEC-RAS to: analytical and text book data sets; lab studies, and real world flood events with good observed data.  This report covers 1D steady flow; 1D unsteady flow, and 2D unsteady flow computations.  The report verifies that HEC-RAS correctly solves the equations used in each of these computational frameworks, and it verifies that HEC-RAS can be used for a very wide range of riverine modeling conditions.  It can aslo be download here:

  1. RD-51 Benchmarking of the HEC-RAS Two-Dimensional Hydraulic Modeling Capabilities

This research document summarizes how the Hydrologic Engineering Center's (HEC) River Analysis System (HEC-RAS) software performed in the two-dimensional (2D) modeling benchmark tests developed by the United Kingdom's (UK) Joint Defra (Department for Environmental Food and Rural Affairs) Environment Agency.  This is an updated version of this report that we previously developed.  We re-ran all of the test, plus one new test, with version 5.0.4 of HEC-RAS.  The results are even better than before, and the HEC-RAS computational speed is much faster than previously document.  This report can be downloaded from our web page at the following link: