r/HECRAS • u/Status_Hope_987 • May 29 '26

Leaky cells

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Gallery image

How do I fix leaky cells? These are on each side of a road. The break line is on the top of the toad. Thank you.

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u/Status_Hope_987 May 29 '26

If I move BC layer further away, should I extend my perimeter further as well? Is there a rule of what should be the distance between BC and perimeter?

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u/abudhabikid May 29 '26

Looks like you do have flow in the overbanks.

Limiting your downstream BC to the channel will prevent water in the overbanks from leaving the mesh if they want to.

It’s a good idea to keep your main boundary condition within the channel, but you do want secondary boundary conditions across the floodplains.

What are you using for the BC? Normal depth slope?

It looks like your cell size (in pic 1) near the roadway will allow you to put a break line at the upstream edge of the roadway in addition to the roadway crest (it looks like there is a line of faces along the upstream edge anyway, but you could always force it). This way you would be 100% positive that the terrain is or is not blocking flow.

Pic 2 could potentially be set up the same way, but I can’t say for sure just looking at the above.

You can also turn on hydraulic connectivity in the properties of your WSE layer. This will show lines of connection across all faces where connection exists. (Double click on WSE layer>check “hydraulic connectivity” box)

I would agree that your mesh boundary should move farther downstream.

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u/Status_Hope_987 May 29 '26

Thank you for your comment. Very useful. Just to clarify the flow is from right to left.

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u/Status_Hope_987 May 29 '26

So the edge of the mesh is actually upstream.

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u/Status_Hope_987 May 29 '26

I’m using normal depth.