July 15, 2024
Virtual Flume
Ven Te Chow’s book “Open Channel Hydraulics” is arguably the gold-standard book for hydraulic engineers-especially those of us who model open channel flow.
Sediment Transport Features in HEC-RAS 5.0
The new 2D features and mapping tools are the most anticipated new features in HEC-RAS 5.0. However, HEC also added a couple major new sediment features, as well as many minor features and a few substantial bug fixes (e.g. SI Units). The two major features are the ARS-USDA Bank Stability and Toe Erosion Model (BSTEM) and Unsteady Sediment transport.
USDA-ARS Bank Stability and Toe Erosion Model (BSTEM)
HEC collaborated with Andrew Simon (Cardno) and Eddy Langendoen (USDA-ARS) to couple the HEC-RAS mobile bed model with the USDA-ARS Bank Stability and Toe Erosion model (BSTEM). This model coupling adds BSTEM’s lateral processes (geotechnical bank failure, groundwater lag and toe scour) to HEC-RAS’ vertical, deposition and erosion processes. This tool has a separate User/Technical Reference manual available from HEC.
Goodwin Creek, MS, repeated right bank surveys compared with computed HEC-RAS/BSTEM cross section migration from Gibson et al. (2015).
Unsteady Sediment Transport:
Previous versions of sediment transport in HEC-RAS used the quasi-unsteady hydraulic model exclusively, simulating hydrodynamics with a series of steady flows. HEC-RAS 5.0 couples the sediment computations with unsteady flow. Hydrologic mass conservation is the biggest advantage of unsteady sediment transport, making reservoir models and even multi-reservoir cascade models much more practical in HEC-RAS. However, coupling sediment transport to the unsteady flow capabilities also brings several powerful features, native to the unsteady hydraulic analysis environment, into sediment transport analyses including: lateral structures, flow networks, mixed flow (figure), and especially operational rules (Gibson and Boyd, 2014). Version 5.0 even includes sediment based operational parameters, operating structures based on bed change and concentration (e.g. TMDL).
Initial and bed profile and water surface elevation for a mixed flow sediment transport simulation with equilibrium sediment load and hard bottom. Sediment deposited in the sub-critical reach.
Other Features:
HEC-RAS 5.0 also includes a range of other new sediment features including:
· HDF5 Sediment Output and a New Sediment Output Viewer
· Copeland (1993) Sorting and Armoring Method (Exner 7 in HEC 6T)
· Gradational Hotstart
· Sediment Flow Splits
· New Dredging Tools
· Bed Roughness Predictors
· New User Manual
· DSS Sediment Time Series Boundary Condition
· Specific Gage Capabilities
HEC-RAS 5.0 will be released shortly. To test a final beta version contact Stanford Gibson at HEC.
References:
Copeland, R (1993) Numerical Modeling of Hydraulic Sorting and Armoring in Alluvial Rivers, PhD Thesis, The University of Iowa, 284 p.
Gibson, S. and Boyd, P. (2014) “Modeling Long Term Alternatives for Sustainable Sediment Management Using Operational Sediment Transport Rules,” Reservoir Sedimentation –Scheiss et al. (eds), 229-236.
Gibson, S., Simon, A., Langendoen, E., Bankhead, N., Shelley, J. (2015) A Physically-Based Channel-Modeling Framework Integrating HEC-RAS Sediment Transport Capabilities and the USDA-ARS Bank-Stability and Toe-Erosion Model (BSTEM), SEDHYD Interagency Sediment Conference, April 2015, In Press.
Comments
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on April 8, 2015Very nice
A. Bilal
on April 17, 2015Dear Stanford and Chris
Thank you for giving a nice overview of sediment transport capabilities of HEC-RAS 5(beta). The question I want ask may or may not make some sense since I am relatively a new HEC-RAS 4.1 user. But still I want to know that are there some instances when a river or channel cannot (or should not) be modeled by HEC RAS 4.1 but can be done in HEC-RAS 5.0. I am specifically talking about in context of sediment transport analysis.
Regards
Ahmed
stanford
on May 5, 2015Hello Ahmed, If the process is fundamentally unsteady, the quasi-unsteady approach in 4.1 (and 5.0) can be inappropriate. The most common example is reservoirs. 4.1 can simulate a singel reservoir if the reservoir stage is the downstream boundary condition. But if you try to model operations through an inline structure or, say, a cascade of reservoirs, the steady flow hydraulics of 4.1 will miss the volume storage. This will affect sediment results. So it is important to use unsteady hydraulics (only available in 5.0) if the system has a lot of storage.
However, there have been many bug fixes since 4.1, so I'd recomend switching to 5.0 for any application at this point.
stanford
Ganesh Ghimire
on September 14, 2015Mr. Gibson,
I have been using HEC-RAS 4.1 as well as 5.0 Beta for the sediment transport and dredging prediction model of Ohio River at Olmsted Locks and Dams area for my MS research. Initially, I have begun with HEC-RAS 4.1 steady flow simulation and QUF for sediment transport model. The reach I have considered is about 10 miles. While performing sediment transport modeling in 4.1 under QUF condition, it displays majority of the deposition in the vicinity of u/s boundary before attaining the equilibrium condition d/s. As a result, there isn’t much deposition at downstream sections as observed from measured data. Is it solely because the sediment inflow series defined at u/s is significantly greater than the transport capacity of river or it’s an artifact of the model itself? I wanted to be sure about the correctness of my model before moving further with HEC-RAS 5.0.
Meanwhile, when can we expect the full version of HEC-RAS 5.0 for public use?
stanford
on September 14, 2015Depositing a bunch of sediment at the upstream cross section is a common problem with sediment transport modeling. It means that the inflowing load, the bed gradation and the transport function are not compatible. When the model over-deposits at the US boundary condition there is either 1) too much sediment or 2) not enough capacity. The first thing I'd try would be a different transport function. Chances are there is an appropriate transport function that will compute higher capacity. Also, make sure flow is contained in the channel or, if not, that you are using ineffective flow areas correctly.
Ganesh Ghimire
on September 18, 2015Thank you Mr. Gibson for your prompt reply.
I have one more difficulty in understanding the model. Though it uses 1D Exner sediment continuity equation during the simulation, I am wondering where and how do we define porosity in the sediment characteristics. In other words, how is it incorporating porosity in the calculations?
Besides, if I am not mistaken the sediment composition we define at the upstream boundary will be used during the sediment mixing process (while checking for sorting and armoring). Am I correct here? Moreover, after series of simulations with the transport functions that are best suited in the sand range, and also updating the bed gradation at u/s, I have been able to reduce the deposition significantly at upstream. But still it is significantly higher than the deposition experienced at site condition. In that case, is it possible to develop the equilibrium sediment rating curve at upstream boundary running the model for each stepped hydrograph? I am looking for your suggestion on how can I approach this problem.
Ganesh Ghimire
on October 30, 2015Hello Mr. Gibson,
Currently, I am trying observe the difference between the prediction in sediment transport trend using the quasi-unsteady and completely unsteady sediment transport module of HEC-RAS 5.0. However, while using the complete unsteady feature of unsteady flow simulation, I couldn't find several sediment output features available under quasi unsteady-simulation. Model is not unstable either and performing fine as far as hydraulics is concerned. In sediment output prompt lots of output options are missing and sediment output (old) menu is not activated either.
Chris Goodell
on October 30, 2015Ganesh- Would you please share your email with me? Thanks-
Chris
Modeler
on December 14, 2015Is it possible to model sediment through an overshot gate?
Chris Goodell
on December 15, 2015I think so. Give it a try.
luis
on January 14, 2016Estimated Stanford and Chris, you can get results of sediment transport in areas 2d? As I get the updated documentation sediment tranport?
Chris Goodell
on February 12, 2016There is no sediment transport in 2D areas yet. Look for it in a future version of HEC-RAS
Bahnisikha Das
on March 4, 2016I am using HECRAS 4.1 and while running the sediment transport analysis, I chose "output Level 6" in the "sediment output options". But I am not getting any sediment discharge in the output. Can you please help me out on this? Thanks in advance.
Chris Goodell
on March 7, 2016Try the new Version 5.0. Perhaps it will work better. http://hecrasmodel.blogspot.com/2016/03/hec-ras-50-official-release-is-available.html
Tija
on March 15, 2016Mr Gibson,
I have used HEC RAS 5.0 Beta (august 2015 release) to set up and run quasy-unsteady sediment model (Si units). I’ve used MPM equation and Exner 5 Sorting method and I’ve achieved quite good calibration results. But now I have ran the same model in new HEC RAS 5.0 model release and the results are significantly different (e.g. Long. cumulative volume change increases 5 times). Input parameters are the same as I’ve only opened and ran the same file with new model release of HEC-RAS 5.0. Are there known to be any significant changes or bug fixes in final release (compared to last Beta release) of the model that could cause such difference in the results?
Thank you for the reply.
Tija
on March 15, 2016Mr Gibson,
I have used HEC RAS 5.0 Beta (august 2015 release) to set up and run quasy-unsteady sediment model (Si units). I’ve used MPM equation and Exner 5 Sorting method and I’ve achieved quite good calibration results. But now I have ran the same model in new HEC RAS 5.0 model release and the results are significantly different (e.g. Long. cumulative volume change increases 5 times). Input parameters are the same as I’ve only opened and ran the same file with new model release of HEC-RAS 5.0. Are there known to be any significant changes or bug fixes in final release (compared to last Beta release) of the model that could cause such difference in the results?
Thank you for the reply.
Tija
on March 15, 2016Mr Gibson,
I have used HEC RAS 5.0 Beta (august 2015 release) to set up and run quasy-unsteady sediment model (Si units). I’ve used MPM equation and Exner 5 Sorting method and I’ve achieved quite good calibration results. But now I have ran the same model in new HEC RAS 5.0 model release and the results are significantly different (e.g. Long. cumulative volume change increases 5 times). Input parameters are the same as I’ve only opened and ran the same file with new model release of HEC-RAS 5.0. Are there known to be any significant changes or bug fixes in final release (compared to last Beta release) of the model that could cause such difference in the results?
Thank you for the reply.
Chris Goodell
on March 15, 2016Nothing known has changed that would affect that kind of difference. If you want, you can send me your dataset and I'll forward it on to HEC.
Pariveeksha Joshi 15210016
on January 20, 2017Mr. Gibbson,
I am a student and currently learning HEC RAS sediment modelling. in using the model i am getting very high sediment deposition (5 m in 15 days). while i am using similar inputs as given in example model (sediment transport simple). the only difference in my model is that it is in SI unit and the channel cross section is rectangular as compared to trapezoidal as given in example. rest all the flow data and sediment data is same as example still i am getting so high deposition but the example model shows deposition of 1 m. what is the possible cause for this?
Unknown
on October 1, 2018Hello sir.,I'm kapil i want ot use hec ras for finding out life of reservoir through sediment analysis but i don't know how can i do. So can anyone gives some idea how i relate hec ras results to life of reservoir.also provide your mail id so can i contact if i'll stuck anywhere. thank you
Unknown
on October 2, 2018hello i'm kapil sir and i'm doing my project to find out the life of reservoir through sediment transport 1D by using hec ras. is this possible?. if yes, how can we do that from result to estimate its life. please help me out.
Unknown
on February 19, 2019Hello!
Is it possible to model sediment transport and sediment deposition (of reservoir) in 2D using any version of HEC-RAS? If yes, please mention the version.
Thank You in advance!
Chris Goodell
on February 19, 2019Not in 2 D areas yet. They are working on it.
Unknown
on June 21, 2019Hello Stanford and Chris,
Thanks for that very interesting article and the overall help you post on this website.
I am currently running a sediment transport simulation for a 46km long reach with a lot of inline structures (small dams, natural enroachments ..)
I was wondering wether there was a way to indicate that we want only the smaller sediments to go over the inline structure (as you can do for lateral structures) instead of having a fraction of each grain class going ove the dam. This result does not represent reality to me (as the dams are not transparent to transport, from field data we know they are filling up). Maybe my physical analysis is wrong, but I hpe you understand my problem,
Regards,
Suzanne
Chris G.
on June 21, 2019I don't know if there is a size exclusion feature in the latest version of HEC-RAS. I've never noticed one before. My guess is it's not in there.
Unknown
on June 24, 2019Thank you for your reply!
Suzanne
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