[Lonnie A]

If you are needing to map the overflow you probably need to have a reach covering the area that receives the overflow. If you are just needing to reduce the flow on the structure by diverting the overflow, a lateral would work. You may want to investigate using 2D to help with setting up a pure 1D model if that is the end model required.
Attached is a couple examples of how in the past I’ve handled modeling what I envision your situation to be.

lateral_weir_usage_tips.pdf

[Lonnie A]

There isn’t a easy way to do this in RAS V5.0.3. A work around is to split the 2D flowarea into 2 or more flow areas and put a “1D storage area” in the area you want to apply hydrograph. Delineate 2D flow areas around the storage area and then connect the storage area to the 2D flow areas with storage area connectors. Now you can insert a hydrograph into the storage area and it can spill over the connectors into the 2D flow areas

[Lonnie A]

I don’t have any experience with this but I believe you might be able to purchase super computer time from Amazon?
https://aws.amazon.com/hpc/

[Lonnie A]

Albern,

These two post by Chris G. may be of help to you.

http://hecrasmodel.blogspot.com/2015/06/lifting-terrain-in-hec-ras-50.html

http://hecrasmodel.blogspot.com/2014/12/including-channel-bathymetry-into-your.html

You will create geometry for the terrain edits in the geometry editor typically.

[Lonnie A]

Either method would work. You will still get a larger than actual volume stored in the high n-value method. Be aware that RAS will only assign one n value per cell face so you need to define your mesh or n value accordingly. RAS is taking which ever n value makes up the largest % of the cell face length as the value it assigns.

[Lonnie A]

One way is to place a 1D storage area between the 2 2d flow areas. You can then link the 3 together with a SA connector and put you inflow hydrograph in the 1D storage area.

[Lonnie A]

I’m assuming you ran V5.0.2 and used the 2D equation on the lateral weirs. There is a bug that HEC has confirmed. If you use the weir equation with a low C-value you’ll not have these “boils”. Hopefully they will have the bug fixed in the upcoming 5.0.3 release.

[Lonnie A]

If you imagine the boundary line being a XS it might help you visualize where to set the limits. RAS is going to essentially cut a XS along the boundary line and when you apply a hydrograph it will fill the XS starting at the low point. So if you have a hydrograph for only one drainage area you don’t want the boundary to cut across into an adjacent drainage area. Or don’t cut across two channels if they have independent hydrographs.

[Lonnie A]

I don’t know if this is the issue but try to avoid having two elevations at the same station. If I have a vertical wall for anything in RAS I’ll code it in with at least a hundredth of a foot difference in station.

[Lonnie A]

Interpolating XS isn’t going to help as that is not the problem.
You need to increase the Htab limits. In the geometry editor on the left side there is a button called HTab Param. If you haven’t opened this before it will be set to what RAS thought would work. First thing is to highlight the starting el column and then hit the “copy invert” so that the Htab start at the channel flowline. If using v4.1 you have a maximum of 100 points so set it at 100 and then adjust the increment so you are above a few feet (or a meter) above the WSE. If v5.0.1 you have more points so have more flexibility. I typically stay around 100 points and increments of .25’+/-.

[Lonnie A]

Ben, You will want to set it to permanent ineffective. There will be some conveyance happening below the berm elevation but not full depth.
You may want to use a combination of a high vertical n value (0.99) to essentially block conveyance below say a foot or two of the berm and ineffective set at the berm elevation so that as water rises on the “wet side” of the berm it doesn’t calculate conveyance in the dry side. Once the berm is topped then it can start using say the top 1 to 2 feet as conveyance with a lower n-value (0.02?).
I would test it out first by just setting permanent ineffective at the berm elevation and then a few feet below the berm and see if it makes much of a difference in computed WSE. If it doesn’t just leave it at the top of the berm. I assume this is a steady state model?

[Lonnie A]

I use the tool linked to below to edit the geotif cell elevations. I’m in no way associated with the company. This is the only tool I’ve found that lets you “somewhat” painlessly edit the surface elevations. It would be nice if RAS would let you edit the minimum elevation in cells that have culverts….

http://www.aris.nl/index.php?option=com_content&view=article&id=210:aris-grid-editor-for-arcmap&catid=64:arcgis-tools&Itemid=169&lang=en

[Lonnie A]

Also check what is in the XS line table under GIS tools for this XS

[Lonnie A]

You say you are running a steady state model. The storage area won’t have an impact on the model as there isn’t a volume associated in steady state that gets diverted.

Now if you aren’t seeing a reduction in flow due to the lateral weir check that you have selected the flow optimization. Plan editor window, options, flow optimizations…

[Lonnie A]

If I’m reading your question correctly, the XS interpolated surface has nothing to do with the geotiff you created. The geotiff you created is a raster that you can use to merge with the terrain.
Chris has a older blog post on this that might help explain
http://hecrasmodel.blogspot.com/2014/12/including-channel-bathymetry-into-your.html

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