topic Re: Cut Only Ditch in Civil 3D Forum

Cut Only Ditch

ecursonmsmm — Tue, 16 Jun 2026 16:22:21 GMT

I need help creating a cut only subassembly (if this is possible). The ditch has a flat constant bottom and each side has a constant side slope to daylight. What I need to remove is the fill aspect of my crude subassembly. Hopefully the pictures will show my intent. Please let me know if any more information is needed.

Re: Cut Only Ditch

cwitzel5NL5H — Tue, 16 Jun 2026 19:22:18 GMT

You might try a Conditional Subassembly. I haven't used them in a long time, but that may work in your situation.

Re: Cut Only Ditch

Radwan-Almsora — Tue, 16 Jun 2026 19:24:59 GMT

Yes, you can create a cut-only ditch subassembly. The easiest method is to use the BasicSideSlopeCutDitch or Ditch subassemblies, or build a custom setup using ConditionalCutOrFill tools in AutoCAD Civil 3D.

To resolve your issue, you can enter here.

Ditch

Re: Cut Only Ditch

ecursonmsmm — Tue, 16 Jun 2026 19:35:31 GMT

I am not seeing a BasicSideSlopeCutDitch subassembly. I do believe I need to create a Conditional Subassembly but I am quite unfamiliar with the tools to do so. Any help would be greatly appreciated.

Re: Cut Only Ditch

AllenJessup — Tue, 16 Jun 2026 20:07:41 GMT

It's on the Basic tab.

Re: Cut Only Ditch

ecursonmsmm — Tue, 16 Jun 2026 20:14:07 GMT

thank you for the response. Unfortunately I don't think that will not work as it has cut and fill in the subassembly and the subassembly start is from a feature where I would need the ditch to be centered on the profile line and baseline. If I am wrong please let me know how I would accomplish this.

Re: Cut Only Ditch

fcernst — Tue, 16 Jun 2026 20:22:43 GMT

Yes you need cut fill conditional subassemblies on each toe left and right then when you’re cut do your outer cut and daylight work and when you’re in fill do nothing. cut work you’re gonna have to daylight as normal going outward, but then daylight coming back at flat slope from the proposed toe location to hit the inner existing channel bank.

Re: Cut Only Ditch

ecursonmsmm — Tue, 16 Jun 2026 21:19:41 GMT

I don't believe you understand what I need. There is no fill in the entire project only cuts. The object is created from the design profile at the centerline. This profile can be below or above existing grade. The width of the ditch is a set width and the slopes are a set percentage. So the ditch could be cutting from top of bank to the other top of bank in one scenario and the opposite scenario it would create nothing as the entire design section could be above grade. If I am misunderstanding your explanation, I don't know exactly what you are trying to articulate.

Re: Cut Only Ditch

fcernst — Tue, 16 Jun 2026 21:22:37 GMT

Yes I understand..that's what my solution does.

"In fill do nothing..'

Re: Cut Only Ditch

ecursonmsmm — Tue, 16 Jun 2026 21:32:52 GMT

Ok I think I have found what you are referring to. I am going to try it out. I didn't realize that particular subassembly was only cut or fill not both and it seems I need to set the bottom slope to 10000000:1 to get a flat bottom. I will let you know if it works out.

Re: Cut Only Ditch

fcernst — Tue, 16 Jun 2026 21:34:28 GMT

maybe you haven’t used the conditionals before ..so I’m talking about at the conditional test point locations, which are your toes left and right ..if your toe ends up in the air that is a fill result..do nothing

Re: Cut Only Ditch

ecursonmsmm — Tue, 16 Jun 2026 21:45:16 GMT

The issue I have now is I have no cooridor anymore. That subassembly does not create points or links to then make the corridor. What am I doing wrong now?

Re: Cut Only Ditch

ecursonmsmm — Tue, 16 Jun 2026 23:02:22 GMT

I see what you are saying now. The issue I am coming across is that I will have more scenarios than I want to count. Maybe I am asking the wrong question. My corridor was fine with the exception of the fills. Is there a way to export only the cut for plan view contours and cross sections?

Re: Cut Only Ditch

fcernst — Tue, 16 Jun 2026 23:34:27 GMT

no it has to be correct. Use generic links for the test links that reach out and do your bidding, but don’t use them in your surface definition.