Hi Dr. Gibson, when I run my model, this error messages popup. I checked all my input data - flow duration and computation increment, all data is more than 0. Can help to clarify why this error keeps happening? Sediment Transport Analysis HEC-RAS 6.x An error occurred with sediment boundary data. The Boundary duration data and Computation Increment Must both be greater than 0.0 Please check your data.
Why go through the hustle of log-transforming the data and using a complicated equation to avoid a transformation bias? Why don't people fit a non-linear model in euclidian space from the get-go? Is it just that log-sapce is better for visualization or is it a historic thing?
Good question. No...it did not. This is an important point. The culvert length stays the same that you specified...the coordinates just determine the headwater and tailwater elevations/cells.
Very cool! This reminds me of how different periods of freezing/thawing (as well as many other processes) create distinct layers of snow and ice crystals over a snow slope - which can be responsible for avalanches.
These Podcasts are really cool, the excerpts with additional complemenary data/videos/graphics makes it super interesting. One thing I would like to see added, is the option of having video format for the whole podcast like Joe Rogan does IT just gives a nice feel to it, Morevoer, these images can be shown in real time, during the podcast with some help ofcourse, Furthermore, these edits can still be continued after the podcasts.
It's so much fun to see a former student! I always wonder what the "kids" are doing with their lives. Congratulations, Stan. Well deserved recognition.
Congrats!!! And thank you for the general tip about using "Rules" for gate controls. I just used it in a Debris Model by assuming the bridge will clog when approximately half amount of material passes through the bridge opening.
Excellent! Very creative. I have done something very similar. We often make blanket assumptions about bridge clogging (e.g. all bridges will clog 50 or 80% except freeways) in debris flow. But clogging them from the start can mess with arrival times (flooding arrives too early). So using a gate to "clog" a "bridge" is a great way to get the best of both worlds.
Very useful, thanks for the lesson! I'm working with this Bingham model in my master thesis. I have a question about the non newtonian Cv parameter: If I set the Cv = 60% and select the "Do Not Bulk" option, then the simulation doesn't take into account the volume concentration? Or is it actually taken into account but its assumed that it is included in the flow hydrograph? (and if so, how does the bulking factor work in this case?) I have been running the model all this time with "do not bulk" option, does this mean I am modeling clear water?
The bulking option assumes your boundary condition is a clear water hydrograph and RAS is adding your solids to it. "Do not bulk" assumes that your boundary hydrograph is a time series of the whole mixture volume.
But, if you use the O'Brian or exponential rheology equations, those use Cv, so you can choose "do not bulk" and still have effects from Cv. If you choose user specified parameters and "do not bulk" the model will be insensitive to your Cv...assuming that you already included it in your boundary hydrograph. HMS includes both options, a bulk mixture hydrograph, or a clear water hydrograph and a Cv time series.
How to export the clone terrain to a raster for use in arcgis or other programs. Tried to use the export raster option, but it just export the image raster.
Interesting! A quick question: how does RAS account for the fluid density of the debris flow mixture, and how to specify the material’s specific grain density? Density is often twice as large as clear water and can have significant impact on flow dynamics. Thanks in advance!
We compute fluid density based on the concentration by volume (CV) in the non-Newtonian fixed bed model, which means that for now we assume the solid phase has a specific gravity of 2.65. I suppose you could estimate higher density material with some sort of "apparent Cv" that converts mass in to volume...but I'd need to think/read more about that. Overall, though, most of the density effects are in the empirical parameters, not the physics, anyway, so I don't think it matters too much. In the mobile-bed sediment transport model you can edit the specific gravity of each grain class and simulate multiple grain density transport....but that is a much bigger effort.
I am going to post a video on Binham parameters in a couple months...if you would like to preview a rough draft, reach out ot me on linkedin and I can give you a link
Hello, i have written to you before. I'm working on my bachelors thesis on HEC-RAS sediment moddeling and have run into an issue while hydraulicaly calibraing my model. I have 6 gates in a SA/2D connections opening based on the rules i've set but based on my previous runs it seems like they dont follow the rules at all in fact most of the gates dont open at all. This has left me and all my professors confused since we do not see any problem with my model. Would you please help me because i have been trying to resolve this issue for over a month now and I'm at my wits end. Thank you very much.
I don't think I've tested connections with rules in a 2D sediment model. There is a chance that that particular confluence of features has a bug. If you believe there is a bug, please send the files to the RAS inbox www.hec.usace.army.mil/contact/
@@stanfordgibson I have not tried adding any sediment data yet because I can't calibrate the model hydraulicaly. I semt an email to the email you have send. I've run more tests and the gates just do not work...
Hi Dr. Gibson, I want to know the difference between the 2D Initial Condition/WarmUp (Ramp Up hours) and the 2D Sediment WarmUp Periods (concentration, gradation & bathymetry). Do I need both warmup parameters for a 2D Sediment analysis or when I'd need to introduce those 3 sediment warmup periods? Thank you so much for your videos!! (I'm from Peru btw)
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?
Is it possible to set up model where there is essentially a dam break of large cobbles and boulders? I was thinking that I could do this by modeling a short burst hydrograph (only a minute long), but am weary that there will be numerical oscillations in the process.
A question: can we run the turbulence model without a sediment transport simulation.I mean just for a 2D inondation mapping ? or not possible because we need to have solutes to solve the equations for the advection.
Yes, you can run turbulence for a simple hydraulic model. It will affect the velocity distribution across the channel. So if you are interested in detailed velocities it can help. But it is essential in sediment because we are so dependent on detailed veleocities.
Hello Gibson, I have been following your videos on RAS analysis, and I find them incredibly helpful. I have a question regarding the datum. You mentioned the High-Water Mark (HWM) elevation as 6.4 feet, and you also mentioned some calculations with terrain. Could you please explain a bit more about your datum and how you arrived at the value of 693.4 feet after performing those calculations? I often get confused between HWM elevation and model projections. For example, I have an HEC-RAS model projected in NAD_1983_UTM_Zone_16N. Additionally, I’ve collected HWM data from USGS, "Black Sharpie mark on red fire hydrant 2.25' above ground in the liberty ball field, hydrant is 9.3 meters from edge of parking lot" measure at 278.9 feet above NAVD88. How can I adjust the HWM height and compare it with the RAS-simulated stage?
Thank you / gracias to everyone involved in the making of this video. This geologic event has been fascinating to watch from afar and it has been very interesting to me!
Hello, Thanks for the video. I'd like to know the HEC-RAS limitations. When we simulate sediment transport, usually we have rivers with steep slopes ( greather than 4%). Which is the max bed slope of the channel that HEC-RAS could handle? could you help me with this question please?
I have a 10' x 10' culvert with water coming out at 17 fps and going into a natural channel. Our 2 ton riprap got washed away with the recent rains here in CA. So now I'm trying to size the riprap so it doesn't get washed away. so I'm making my upstream reference section to be the culvert which has the most velocity. The design section is about 15 ' downstream and I'm using that. So now the question: What section is used for the input data? It's all straight so there is no radius. But the side slope of the reference section is 90 and the side slope of the design section is 35 in the natural channel. So what numbers do I use?
You can only calibrate to data you have...so you could still do a quasi-1D calibration to high water marks (preferably for multiple flows). It won't resolve your lateral velocity distribution (which is important for sediment) but is MUCH better than not calibrating.
Hello Stanford, I hope this message finds you well. I wanted to commend you on the superb content and engaging work you've been producing. I have a question regarding the "Concentration Only" Mode. Currently, I am in the process of calibrating experiments conducted by GUTA at LEGI LAB Grenoble, France, using HEC-RAS 2D. The setup involves different settings of incoming loads (below capacity) categorized as LOW, MED, and HIGH, with a flume width of 0.35m. I've encountered a few challenges: 1. Firstly, I am working with a particle density of 1192 kg/m³. Utilizing "User Defined Grain Classes," I inputted SG = 1.192 and BD = 655.6 kg/m³ with a porosity of 45%. I also adjusted the classes' diameters as required. My question is, does this approach work effectively? 2. Secondly, when inputting the upstream inflow boundary condition, whether using the Rating Curve or Time Series, I entered a value of 2 tonnes/day, which translates to 0.078 kg/m/s. However, the Results Map for "Total Load Transport Capacity" is indicating a significantly lower value of about 0.003 kg/m/s. Which Results Map should I refer to for the sediment rate or flux? I find it peculiar that the induced value is not reflected accurately in the model. Any insights on this discrepancy would be greatly appreciated. 3. Thirdly , is there a way to separate the sediment boundary condition from the flow boundary location? In the lab flume, the inflow is controlled by a hopper/funnel, positioned precisely. Is there a workaround for this? Your expertise and guidance on these matters would be invaluable. Thank you for your time and assistance. 4. Lastly, I'm interested in understanding how to utilize the Non-Erodible Method in Adaptation Parameters. Could you please provide guidance on its implementation?
