Wednesday, January 16, 2019

Bug Report for HEC-RAS 5.0.6

RAS Users:  Please give this "Known Issues" report a read if you're using Version 5.0.6.  If you've been doing a lot of 2D modeling, it's likely you have been affected by some of these.



This link includes a document of "Known Issues" found in version 5.0.6 of HEC-RAS to date.  The
document outlines all of the Issues (bugs) we have found so far.


Please look closely at this document, as there as a few issues that are potential computational problems.  Specifically issues 1, 2, 5, and 7.  Please review these issues closely.  If you have any of these situations use the suggested work around, or solution to get past the issue.  Everyone should look at issue 1 and 2, as they are possible in many models.

Sorry for any inconvenience this may cause you.  Keep letting us know if you find other problems with the software.


Gary W. Brunner, P.E., D. WRE, M. ASCE
Senior Technical Hydraulic Engineer
Hydrologic Engineering Center, USACE

Friday, January 11, 2019

Preview of the new Finite-Volume Approach for 1D Reaches

One of the most anticipated new features soon to come in the next major version of HEC-RAS (Version 5.1) is the option of running unsteady 1D reaches with a finite volume solution scheme.  This will be a fantastic addition to HEC-RAS.  Gary Brunner recently gave me a brief overview of the new finite volume feature we can expect.  But before you ask, there is no set release date for Version 5.1 yet.  But I'm hoping we'll see it within the next year or two.





1D Finite Volume Solution Algorithm

By Gary W. Brunner, P.E., D.WRE
Senior Technical Hydraulic Engineer
Hydrologic Engineering Center

A brand new solution algorithm has been developed for 1D modeling.  A Finite-Volume solution approach, similar to what was added for 2D modeling will be available for 1D modeling in HEC-RAS version 5.1.

The current 1D Finite Difference solution scheme has the following deficiencies:
  1. Cannot handle starting or going dry in a cross section
  2. Low flow model stability issues with irregular cross section data
  3. Extremely rapidly rising hydrographs can be difficult to get stable
  4. Mixed flow regime (i.e. flow transitions) approach is approximate
  5. Stream junctions do not transfer momentum

The new 1D Finite Volume approach has the following positive attributes:
  1. Can start with cross sections completely dry, or they can go dry during a simulation (wetting/drying)
  2. Very stable for low flow modeling
  3. Can handle extremely rapidly rising hydrographs without going unstable
  4. Handles subcritical to supercritical flow, and hydraulic jumps better.
  5. Junction analysis is performed as a single 2D cell when connecting 1D reaches (continuity and momentum is conserved through the junction).


Additionally, the new 1D Finite Volume approached is solved in the same matrix as the 2D equations.  Solving in the same matrix allows for faster 1D/2D model solutions and more accurate flow transfers between 1D and 2D elements.  The equations are solved together and all hydraulic connections are updated together on an iteration by iteration approach, rather than separately, as in previous versions of HEC-RAS.

Monday, January 7, 2019

Removing bridge decks from terrain surfaces

Written by Krey Price  |  Surface Water Solutions
Copyright © The RAS Solution 2019.  All rights reserved. 

Using RAS Mapper as a GIS Tool Part 1:
Removing Bridge Decks from Terrain Surfaces


This is the first in a three-part series on using RAS Mapper as a GIS tool. In this post we'll cover the removal of bridge decks from terrain data.


This topic comes up fairly frequently, since LiDAR data may be inconsistent in terms of the inclusion or exclusion of bridge decks. Depending on how you would like to model a bridge, you may prefer to have the bridge deck represented as terrain or as a deck/roadway defined with station/elevation points (in which case the deck geometry might be best excluded from the terrain data). In either case, you may find yourself needing to modify terrain data to suit your modeling needs.


In a previous post on terrain modification, we covered how to burn channels, levees, buildings, basins, and other features into your terrain surface using RAS Mapper. One application we left off (because it is the example covered in the HEC-RAS manual) is the removal of bridge decks; given some of the feedback we received on the previous post, we thought it might be worth including bridge decks in the process as well.


The process of removing a bridge is actually quite simple, as is the process of inserting some basic deck geometry into your terrain data. We walk through the complete steps for both removing and adding a bridge in less than 5 minutes in this video walk-through:



https://youtu.be/MWYKW-6D0FU


Here's a screen shot of Page 2-11 in the HEC-RAS 2D User Manual showing a bridge deck included in the terrain data and then removed from the terrain data. Now you see it, now you don't:





The following images are courtesy of Cameron Paintin from Riley Consultants, who applied these steps for a project in New Zealand.


Here is the terrain surface with the bridge deck in it:






Here is a satellite image with the bridge:







In this screen shot, Cameron has drawn a river reach with cross sections on either side of the bridge:







This process can be repeated with additional reaches for any other bridges in your terrain. The following screen shot shows the interpolation surface created by the bounding cross sections:






And the final image shows interpolation surface on top of the terrain to blend out the bridge:







Let us know what you think or if you have other suggestions for improving these processes.



And a happy 2019 to all of the fellow HEC-RASlers around the world!






Monday, December 31, 2018

Using a HEC-RAS Storage Area and Lateral Structures to Replace Standard Reach Junctions

Written by Lonnie Anderson, P.E., CFM  |  Pape-Dawson Engineers, Inc.
Copyright © The RAS Solution 2018.  All rights reserved.


Situation:

Advances in HEC-RAS now allow for improved simulation of overbanks using 2D Flow Areas. Coupled 1D/2D models where 1D cross-sections represent the bank-to-bank cross-section data and 2D flow areas represent overbank areas has greatly improved the accuracy and robustness of HEC-RAS models. This is particularly the case in flat, urban areas with significant overbank flow paths.

These coupled 1D/2D models have highlighted several simplifications and shortcomings of the traditional HEC-RAS Junction methodology. Note that the standard method is still required in 1D steady flow modeling.  The following points suggest an alternative Junction method is worth considering when building a coupled 1D/2D model.


 Figure 1 - Traditional HEC-RAS Junction Methodology with a Coupled 1D/2D Unsteady Model - Simple Junction


  • 1D to 2D offline flow transfer over the junction length is not possible in HEC-RAS.  In other words, a lateral structure cannot span across a junction. In complex confluences, this transfer region may be critical. Simply reducing the distance between bounding cross-sections to minimize this region may not be an option depending on the channel and bank alignments (see Figure 1). 

  • The volume of water within the bounding cross-sections of junctions is not accounted for, whether forcing the water surface elevation to match the downstream bounding cross-section or using the Standard Step one dimensional Energy equation. Both solution techniques simplify the hydraulics of the region, and in particular, the main reach which conveys the greatest volume (see Figure 1).

Simplification of Junction hydraulics has been “accepted” as reasonable, as                          demonstrated by the following guidance from the USACE-HEC: 

Friday, December 7, 2018

Free Webinar on Dam Breach Modeling


Webinar: Dam Breach Modelling


Colleagues-

I'm honored to join Krey Price and Bill Syme in presenting a brief webinar on dam breach modeling hosted by ICEWaRM and the Australian Water School.  Half hour presentation followed by discussion and a Q&A session.  Please join if you can.





https://www.icewarm.com.au/australian-water-school/short-courses/course/dambreak-modelling/

A vigorous discussion with a group of highly regarded dam breach modellers
Approaches to dam breach modelling vary greatly when estimating the discharge through the breach and potential downstream inundation impacts.

This webinar will address 3 key issues:
1) upstream of the dam (reservoir) Krey Price 5 min
2) the dam itself (breach parameters) Chris Goodell 10-12 min
3) downstream of the dam (flood wave routing) Bill Syme 10-12 min

The different approaches to generating the breach hydrograph, the numerical modelling of downstream flood inundation, benchmarking of solution schemes, and uncertainties associated with the modelling will be presented and explored.
Click the link below for more information and to register.

Tuesday, November 6, 2018

HEC-RAS 5.0.6 has been released!

HEC has just released HEC-RAS Version 5.0.6.  This is primarily a bug fix version.  After you've downloaded the new version, make sure to give the release notes a read to see what bugs have been fixed.  See message below from the RAS Team.


All,

             We have released a new version of HEC-RAS today called version 5.0.6.  Please review the attached release notes to see all of the bugs that were fixed for this release.  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 5.0.6 download area of our webpage:

               
RAS Team



Monday, October 8, 2018

Using the HEC-RAS Controller with the R programming environment


Hey all HEC-RAS Controllers-

Charlie Ferguson of the University of Cambridge recently emailed me about some questions about automating HEC-RAS using the HECRASController and the R programming environment.  While "Breaking the HEC-RAS Code" was written around use of VBA for automating HEC-RAS, there are several other programming languages out there that will work.  R is a powerful programming language for statistical computing and graphics.  I've seen it used before and it is quite impressive.  In talking with folks interested in automating HEC-RAS, besides VBA and Visual Studio, Python and R seem to be the programming languages/platforms most people are talking about.  You can read up more on R here.  


Unfortunately I don't have experience using R (yet).  So I'm opening this up to the HECRASController community out there for assistance.  The following is Mr. Ferguson's call for help and collaboration regarding automating HEC-RAS using R.  Please comment below and respond directly to Mr. Ferguson if you wish to share ideas.


The HEC RAS Controller has been used in several different environments (VBA, Matlab etc.) and I am trying to establish how to get it working in R. From what I can find online, there have already been several attempts and would really appreciate any advice or collaboration.

So far I have followed a similar process to ‘Toby’ in this post on the online HEC RAS Controller help forum. The process relies on an R package called R-DCOMClient. A slight difference in my script is to construct the variable ‘strMessages’ as an empty character matrix;
-------
strMessages<-matrix(character())
--------
which appears to satisfy the data type required by the underlying COM method (Compute_CurrentPlan).

However, I’ve then found another error stemming from R-DCOMClient requiring a related R package called ‘R-DCOMServer’. Unfortunately, as far as I’m aware, this package and its prerequisites are no longer available (also, for separate reasons, I need to use an R version no older than 3.1.).  This means I’ve hit a dead-end.

I am wondering whether anyone has found a way past this problem OR has found an entirely different solution for running controller in R?

Any advice or offers to collaborate would be welcome!