Modeling an upground reservoir in a 2D model

[Chris Hauser]

I am working on a “dam-breach” model of an upground (“offline”) reservoir surrounded by very flat terrain. I need to model a breach of this reservoir on each of its four sides. The berms on each side are about 15 feet above the surrounding terrain. There are no “spillways”. Breaching would be by piping failure without any inflows into the reservoir. I would therefore need to create a 2D unsteady flow model in HEC-RAS due to overland flow in the flat terrain from the breaches.

Is it possible to create or “carve out” a storage area for my reservoir within a SINGLE 2D flow area? What would be the basic steps to set this up?

[Luis Partida]

No you cant carve out like that. You could do two 2D areas and connect them with SA connectors.

[Chris Hauser]

Thanks Luis. I have tried that before, in which I create a Storage Area, then I create two “C-shaped” 2D flow areas that together completely surround the storage area. The two flow areas also meet each other at the top and bottom ends of the “C”s.

It does get a bit tricky sometimes to get the two connections between the flow areas at the ends of the “C”s to work properly, unless there happens to be a convenient “ridge” like a roadway berm to act as the “border” connecting the two flow areas. Thus, why I wanted to know how others have approached this problem of laying out an upground reservoir in a flat area.

[Luis Partida]

Hey Chris, have you also considered building the reservoir in the terrain with a terrain modification? You then could potentially use SA connecters within a single mesh to enter the breach rules surrounding the elevated reservoir…just thinking out loud

[Chris Hauser]

Luis-

I had thought that doing that would require making the Reservoir a “separate” flow area mesh, but perhaps I was mistaken about that. I will give that a try.

Thanks!

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