Intro to HEC-RAS Sediment Demo (Part 3 of 3 - Simulation and Output)

[@jayrex0093]

Thank you so much for making these videos (parts 1-3)...just helped me alot with my thesis work. Appreciate!!!

[@Klaus-om8gj]

Very great your sediment videos! Congratulations! I would be very happy to see more videos, good luck!

[@praveenchaudhary5199]

wow! this is great! very helpful and informative. please keep on creating such videos.

[@stanfordgibson]

Feel free to request HEC-RAS sediment topics for future videos in the comments.

[@mjimenez8]

Are there any plans to make similar videos but for unsteady sediment modelling?

[@brian_jk951]

Thank you Gibson. This tutorial has really been helpful. I have an inquiry about how Hec-Ras can model the sediment deposition in open urban drainage channels and how I can simulate this in the different channel shapes such as a rectangular channel with a triangular bottom. Thank you

[@davidfrench7]

Thanks for the tutorial, Stanford. Did you ever end up creating a calibration tutorial? And in reference to part 2, the sediment transport function tutorial/discussion?

[@fengk9628]

so nice video

[@hydrologicmodeling9020]

Excellent video!

[@mohdafiqharun9689]

Thanks for the great tutorial on sediment transport. Can you elaborate more on the calibration and validation for the model?

[@CherryPierogi]

What is the equivalent setting to turning on the "update between mixing time steps" in HEC-RAS 6.3?

[@Klaus-om8gj]

Hello, I have a question regarding the new HEC-RAS 6.0 Beta 3 version. Can it be that an activation of the hiding functions is possible on the user interface, but is not yet applied in the calculation code? Kind regards from Italy

[@stanfordgibson]

Hello. If that is true, its a bug. Hiding should be working. If you send me your files at [e-mail] I'll try to look at them

[@Klaus-om8gj]

@@stanfordgibson Thankyou, you have received an email

[@Klaus-om8gj]

@@stanfordgibson Dear Mr Gibson, I wanted to ask again whether it is already known whether the hiding function calculates incorrectly or not? Kind regards

[@ujjwalmarasini9119]

Thank you for wonderful series, my question is how can i be sure that the result thus obtained is okey? How can the result be validated ???

[@patrickfassell1891]

When I try and run a model with a dataset and following the instructions in the videos I get the following error: An error occurred while reading sediment data at (blank) review your data at this location for completeness and consistency I checked and there is bed gradation data and all my cross sections and I am testing out my downstream boundary condition as equilibrium load to rule out any errors. What is the overall meaning of this error and how do I fix it?

[@stanfordgibson]

Usually some of your initial conditions data is not complete...you are missing gradations or control volume values at one or more cross sections

[@Klaus-om8gj]

Hello Mr Gibson! I have another question... Is there a possibility to change the roughness coefficient depending on the flow rate when using quasi-unsteady flow? Many thanks and greetings from Italy

[@stanfordgibson]

Hello TT, Great question. Flow-dependent n values are very important, and I almost always use them in unsteady, steady, or quasi-unsteady. There are several ways to do this, but my preference is just as a geometry level variable (so it is transparent to what flow model you use). In the geometry editor go to Tools-->Flow Roughness Factors. That should work regardless of how you specify flow.

[@stanfordgibson]

You could also check out the bed-roughness predictors, which update roughness based on sediment transport. These can be sensitive and aren't always useful. but are worth knowing about

[@stanfordgibson]

www.hec.usace.army.mil/confluence/rasdocs/rassed1d/1d-sediment-transport-user-s-manual/simulating-sediment-transport/sediment-computation-options-and-tolerances/bed-roughness-predictors

[@stanfordgibson]

www.hec.usace.army.mil/confluence/rasdocs/rassed1d/1d-sediment-transport-user-s-manual/simulating-sediment-transport/sediment-computation-options-and-tolerances/bed-roughness-predictors

[@Klaus-om8gj]

@@stanfordgibson Thank you very much for your quick and detailed answer! Very helpful, thank you! Also, great new paper regarding sediment and ice‐affected flood‐risk projections! Great job!

[@SanyamGhimire]

Are there any plans for making other similar videos relating to methods of selecting transport function?

[@eng.shereen300]

Can I use this software for sediment transport in the rills and gullies?

[@Klaus-om8gj]

As I mentioned before, you have done a great job with the video, congratulations. But with my application not everything works as planned. I always get the error message "no flow in channel at river/station xxx (channel may have overfilled with sediment)". Could you possibly help me?

[@stanfordgibson]

I should do a video on this error. It is the most common error, and there are several different possible problems.

[@stanfordgibson]

Basically, that means your channel filled with sediment very quickly. The most common reason for that is that the time step is too large. The channel doesn't have time to update the hydraulics in response to deposition. But if it is happening at the upstream cross section, it is usually because the sediment load in the boundary condition is too coarse (often because the user used the bed gradation for the load gradation...but the bed gradation is usually much coarser than the load). This could also happen when the sediment load is too high or the transport function isn’t appropriate.

[@stanfordgibson]

It can also happen if you are depositing in your channel but not you overbank, so the channel thalweg rises above the overbank elevation. This allows all the flow to go to the overbank and dries the channel. Or if you have a cross section that just has a depression in the overbank that is lower than the thalweg, it can divert the water (an ineffective flow area should fix that).

[@Klaus-om8gj]

@@stanfordgibson I'm really looking forward to the video. Thanks and greets from Italy

[@zorankaufmann2289]

At 11:25 in your video you present the invert change profile plot. It appears that the bed elevation does not change regularly between two profiles (it zigzags) which is a little surprising. I get the same type of results with my sedimentary model. The phenomenon of "saw tooth" is a little developed in the chapter "cross section weigting factor" of the user manual (17-61). It is indicated that by changing the weighting scheme of the hydraulic tables associated with cross sections (for example 0.25 / 0.5 / 0.25 or 0/1/0) it is possible to eliminate this artifact. I tried both weights but I get the same result... Could you further detail this point in a video? Thank you

[@stanfordgibson]

A mild saw tooth pattern (like the one you see in the video) is an artifact of sediment model results. Because XSs (or 2D cells) are not a census of reality but a sample, transport tends to fluctuate randomly between them. Therefore, they tend to alternate "slightly more transportable" and "slightly less transportable" - which leads to erosion-deposition cycles. The closer you are to equilibrium the more apparent this pattern is...because noise>signal. But in strongly deposition or erosional environments, the directional effects wash out these minor numerical variations (signal>noise). This is also why we tend to evaluate and present results with the longitudinal cumulative result, because it integrates these fluctuations into a coherent description of the system response.

[@stanfordgibson]

The XS weighting is a relic feature that HEC-RAS adopted from HEC 6, but it actually makes the problem it was meant to solve worse. Particularly when the channel is uniform, weighting results generates "leap frog" type instabilities and generates an aggressive saw tooth. The 0/1/0 default entirely resolves this artifact in uniform channels. In natural channels, the 0/1/0 default is the most stable - but it doesn't get rid of the longitudinal variability.

[@stanfordgibson]

Also, thanks for reading the user manual.

[@NadeemKhan-bu5cr]

sir how to make an meandering river in hec ras?

[@vineelgundala6612]

Hello Gibson, I tried modelling but there was an error showing, Upstream Reach has Zero flow value! What does this mean please help me out

[@stanfordgibson]

Hello Vineel, there is a section of the user manual dedicated to error messages, including this one. Check that out and see if it helps: www.hec.usace.army.mil/confluence/rasdocs/rassed1d/1d-sediment-transport-user-s-manual/trouble-shooting/common-sediment-transport-error-messages

[@stanfordgibson]

It includes three common sources of this error

[@vineelgundala6612]

Got it👍👍, Thankyou

[@abdulmaliksutantio2142]

Hello, sir, I have a problem with my simulated sediment in HEC-RAS. While running my model I get an error message that reads: River: "Sebayur river" Range: "Hulukehilir" RS = 14790 - has zero flow value. What am I seeing? what should i do to solve this problem? please can you help me Thank you in advance for your answers.

[@stanfordgibson]

I am working on a video on common error messages, but it will be a while before I get it out. I have a section on this one in the new RAS manual for 6.0

[@stanfordgibson]

Here it is: Another common pre-Run error indicates that a flow boundary condition has a zero flow value HEC-RAS cannot specify a zero flow external boundary condition. However, more often, this error is the result of: 1. Mis-formatted Date: If the Fixed Start Time or the simulation time window is defined with a date that does not conform to the HEC-RAS DDMMMYYYY convention the date will not register correctly. 2. Non-English Settings, Months, or Special Characters: The months also have to be in English. The following table includes the only MMM abbreviations RAS accepts. JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Additionally, in order to accept dates, the Microsoft language settings on your computer must be set to English (US). 3. End Date earlier than the Start Date: Another common error includes specifying an end date later than the start date (e.g. setting up a water year run but failing to change the second date):

[@stanfordgibson]

I assume it is a non-English date or computer setting. I will try to make that error message more informative in version 6.0

[@Soufffy]

Hello, Thanks for your very usefull videos. I have built a model on hec-ras ans I have some bugs in my sediment outputs : 1/ the simulation time window when I run the model is different to my results’ time windows (same duration but at different times : I run the model from 30DEC1989 to 29 DEC1990, but in sediment Output, the results on profils and XS are from 01DEC1988 to 29NOV1989 and the results on Time Series are from 30DEC1899 to 29DEC1900). 2/ At the same station, I calculate (last time step's Invert Elevation) - (first time step's Invert Elevation), and the result is not the same as last time step 's Invert Change. I would like to know if you have already encounter such problems? Thanks in advance for your answers, Best regards,

[@stanfordgibson]

Hi Sophie. Neither of those sound familiar. Send me a message at and I can take a look at your model.

[@Soufffy]

@@stanfordgibson Thank u very much, I didn't except this answer :) I sand you my model

[@centreofexcellenceinwaterr7696]

That was very good tutorial. Thank you much it really helped. I am working on sediment transport modelling of a reservoir. Theme of the project is to to predict the bed changes for the next 100 years. How can i model the future bed changes due to sediment inflow.?? Can you please help me with that?

[@stanfordgibson]

This is a very common application of RAS-sediment. In fact, it will be one of the next videos. Until then (might be a few months) we have a few publications that might help. Look up my profile on research gate or message me through that platform and I can send them to you. Negotiating Hydrologic Uncertainty in Long Term Reservoir Sediment Models: Simulating Argandab Reservoir Deposition with HEC-RAS www.researchgate.net/publication/327280661_Negotiating_Hydrologic_Uncertainty_in_Long_Term_Reservoir_Sediment_Models_Simulating_Argandab_Reservoir_Deposition_with_HEC-RAS New One-Dimensional Sediment Features in HEC-RAS 5.0 and 5.1 www.researchgate.net/publication/317073446_New_One-Dimensional_Sediment_Features_in_HEC-RAS_50_and_51 Modeling Sediment Concentrations During a Drawdown Reservoir Flush: Simulating the Fall Creek Operations with HEC-RAS

[@deiwakarsingh2508]

Hello Sir, I am a Master's Student and doing my project on the sediment transport model. These three tutorials help me a lot to understand the basics. Dear Sir, I have a couple of questions. First, I followed all the steps, used the datasets provided in the tutorial, and ran the simulation in HEC-RAS 6.0 version. It showed some difference in output results when I saw the graph. Can it be possible, Sir? 2nd question is that I have to add a bridge and then analyze Scouring through this model. How can I do it? From where should I start? I am eagerly waiting for your positive response, Sir.

[@stanfordgibson]

1. It is possible that some setting is different, that you did something slightly different (sediment results can be surprisingly sensitive) or that there is a computational difference in 6.1.

[@stanfordgibson]

2. You want to be careful adding a bridge. 1D Quasi-unsteady is not appropriate for local bridge scour. It is ok for long term deposition in a backwater behind a bridge or maybe a very rough estimate of long term contraction scour, but bridge scour from piers or abutments is a multi-D process that multi-D models don't do great.

[@stanfordgibson]

2b. Plus the sediment computations struggle with the internal XSs in RAS. I have a whole section in the documentation (and may eventually do a video) on bridges in 1D sediment models...use with care: www.hec.usace.army.mil/confluence/rasdocs/rassed1d/1d-sediment-transport-user-s-manual/geometric-considerations-for-a-sediment-transport-model/modeling-bridges-in-a-sediment-simulation

[@stanfordgibson]

2c. Best practice for 1D bridge scour in RAS is to use the HEC 18 Scour calculator: www.hec.usace.army.mil/confluence/rasdocs/rasum/latest/hydraulic-design-hd-calculators/computing-scour-at-bridges

[@deiwakarsingh2508]

@@stanfordgibson thank you sir. ❤️🙏. Let me do now

[@ishratdollan3787]

Thanks for the great video. I followed all the steps and used the datasets provided in the tutorial.I was not able to compute the sediment transport. It gave me an error saying Rs-1000 has zero flow value. What would be the reason? Thank you!

[@stanfordgibson]

That usually means that there is a data error in the upstream quasi-unsteady flow data. It is often a computational increment. Check that data (see minute 325 in the first video).

[@ishratdollan3787]

@@stanfordgibson Thank you. I solved the issue. I did not type the date format as English date format in my plan file. That's why I got that error message.

[@ariahasthawicaksanagede9536]

YES SAME WIMEE :(

[@Aleks1986123]

Great. I have a question. Can you model secondary lahars (sediment transport dynamics) using HEC RAS?

[@stanfordgibson]

As I understand it, Lahars really require Non-Newtonian transport. HEC has added rheological, fixed bed, NN modeling to unsteady 1D and 2D in 5.1 and is beta testing it right now (we are currently validating the model with the USGS volcanic laboratory flume results). Development for mobile bed NN transport is planned but has not started.

[@Aleks1986123]

@@stanfordgibson Thanks a lot. What kind of restrictions do you consider important in order to model secondary lahars (rain triggered lahars) with HEC RAS?

[@stanfordgibson]

@@Aleks1986123 Slopes over 10% or concentration over 10% (by volume) would violate some of the basic assumptions of the model, and the model is currently a continuity based scheme, so it won't track the front very well (even if the Newtonian assumption holds).

[@rodrigoperdigao9074]

Hi Sir, can you please give me some advice on how to set my Bed exchange iterations per time (SPI) and the computation increment of my model? I'm getting some errors like " Unrealistic Vertical Adjustment " and "The active layer completely eroded at one or more cross sections" and I'm wordering if I should use small values for computation increment and SPI.

[@stanfordgibson]

I have a section on unrealistic vertical adjustment in the user manual that could be helpful: www.hec.usace.army.mil/confluence/rasdocs/rassed1d/1d-sediment-transport-user-s-manual/trouble-shooting/common-sediment-transport-error-messages#CommonSedimentTransportErrorMessages-UnrealisticVerticalAdjustment

[@stanfordgibson]

The rule of thumb with SPI is to increase it until the result doesn't change (and you don't exhaust the active layer). You could also make the active layer thicker (see "Mixing Options"). But my guess is that the bed gradation and transport function are mismatched.

[@stanfordgibson]

I actually have a video started on unrealistic vertical adjustment because it is the most common error message...but I'm not sure when I'll get to finishing it.

[@rodrigoperdigao9074]

@Stanford Gibson Thank you very much, Sir! Your videos and manuals helped me a lot! I adjusted the transport function and my simulations are running better. I'll adjust SPI parameter like you said.

[@rodrigoperdigao9074]

@@stanfordgibson That's great news! I hope you can finish as soon as possible. Thanks for that!

[@muhammadarief1401]

Hallo sir, i have a problem when i compute sediment data. i have a message like this "Flow or Temp time series date is not sufficient to run requested time window." what should i do? i've repair that but still error. thankyou.

[@stanfordgibson]

Hello Muhammed, this is a very common and frustrating error. I have a whole section on it in the 6.0 user manual which we will release soon and plan to do a video on it. But for now, here are the possibilities.

[@stanfordgibson]

This message indicates that one of the flow, temperature, or sediment time series in the quasi-unsteady or sediment data do not span the computational interval. Check to make sure that all the time series start at or before the simulation start time and end at or after the simulation end time. However, other data errors, which can be harder to find can generate this error. Here are three common culprits:

[@stanfordgibson]

1. No Temperature Data: Temperature data is mandatory, but requires pressing a button on the quasi-unsteady flow editor. Blank temperature data will return this error.

[@stanfordgibson]

2. Blank or mistaken Fixed Start Time in one of the flow boundary conditons

[@stanfordgibson]

3. Missing Computation Increments. A quasi-unsteady time series can span the entire simulation time window, but if one or more flows lack computation increments HEC-RAS will return this error. If the Automated Computation Increment tool does not span the range of flows, it will leave Computation Increments blank and return this error.