HEC-RAS Sediment Transport Gradations: Three common errors

[@modellazioneidraulicagis]

Great video Stanford thanks. in HEC-RAS for sediment transport the biggest problem in my opion it's create correct Rating Curve. You have in plan make a video for that? Thanks

[@stanfordgibson]

You are in luck. That one is next and is almost done. I'll post it next week. We also are developing a cool new analysis tool to help.

[@modellazioneidraulicagis]

@@stanfordgibson Thank you!

[@wellmanlake]

@@stanfordgibson Is this already online?!?! Both the video and the tool?? Thank you so much for taking the time doing this videos. Well produced well explained!

[@stanfordgibson]

@@wellmanlake The video is online: kzbin.info/www/bejne/mXPVZH6hgbmKZ7s We expect the tool to come out with version 6.2 - hopefully by December 2020 (but look for it in 6.1 - there is a chance it gets in there).

[@stanfordgibson]

*December 2021

[@rajeevshrestha6175]

What if we have to define the boundary condition such that the sediment is coming out of the system?

[@stanfordgibson]

If you need to remove sediment from a reach you have four options. 1. You can dredge (I have a video on that) 2. If you use a negative sediment load in a sediment time series bc it will remove sediment 3. In an unsteady model a lateral structure can take sediment out of the reach or, 4. there is a "Diversion rating curve" that is a little tough to understand, but intended for that purpose. www.hec.usace.army.mil/confluence/rasdocs/rassed1d/1d-sediment-transport-user-s-manual/entering-and-editing-sediment-data/sediment-boundary-conditions/rating-curve/diversion-load

[@rajeevshrestha6175]

@@stanfordgibson I have been trying that in 2D to increase the sediment output through a diversion. But no matter what I do, output is the same.

[@stanfordgibson]

@@rajeevshrestha6175 oh, yeah, I have never tried any of those for 2d yet. I’m sure the diversion won’t work for 2d, I should put a 1d only tag on it. We are hoping to get two dimensional dredging into version 6.4 or 6.5. I haven’t tested a lateral structure with sediment in two dimensions. I suspect your best chance will be a negative time series, either manual or DSS. Please make a note here if any of those work, and I’ll test them as well. Maybe we can make one of those available in the next version if not

[@rajeevshrestha6175]

@@stanfordgibson Thank you for the reply. From what i have been working on, lateral structure doesn't seem to be working with 2D as of now. Also, I tried the negative time series. It is strange but I get only 10% of sediment diverted through the diversion. Maybe it is proportional to the flow that is being diverted. I will post an update if I find something else. :)

[@MahletKinfe-j5m]

@rajeevshrestha did you found any solution for this ?

[@davidedimauro4804]

Hey Stan, in cases where you don't have any input flux gradation data, would you condone performing the Sediment Transport Capacity feature from the Hydraulic Design function first, and use those rating curves as your flux in your sediment transport modelling instead of running your model in an equilibrium state?

[@stanfordgibson]

I should do a video on this. You could do that. But what I tend to do instead is just run equilibrium load in the sediment model for a series of very short increasing flows. Then you can go to the new rating curve output in the sediment results viewer To see the flow load relationship more easily

[@stanfordgibson]

Check out the new overload/underload feature in version 6.2. It gives you the opportunity to scale the equilibrium load. That’s also really useful if you want to get a heavy or light rating curve

[@stanfordgibson]

But remember, equilibrium load excludes wash load, and is heavily dependent on the active Layer gradation. So I almost never use equilibrium load as the boundary condition, but do exactly what you are describing. I use equilibrium load to compute a rating curve which I then use as my calibration factor

[@stanfordgibson]

I should make this an automatic feature, where you can pre-process an equilibrium load into a rating curve with gradation breakdowns

[@davidedimauro4804]

Hi Stanford! Good one! Do you happen to know when HEC-RAS 6.0 will come out? I will settle for the beta version.

[@stanfordgibson]

Hello Davide, We are in the final QAQC push for the 6.0 beta release. That part of the software lifecycle turns out to be a little tough when we aren't co-located. I don't speculate about release dates any more...but we're close. 6.0 has a lot of new functionality to test, so it is taking a while. But its going to be cool!

[@davidedimauro4804]

@@stanfordgibson thank you! Is it going to be distributed to alpha testers first or is it going to be available to everyone as soon as it's released?

[@stanfordgibson]

@@davidedimauro4804 We decided to go straight to a public beta apart from a little internal testing. So my offers to share an alpha version in some of these videos turned out to not be something I could do.

[@davidedimauro4804]

@@stanfordgibson Yeah I figured. I was one of them requesting a copy haha

[@stanfordgibson]

@@davidedimauro4804 The beta version is on the website