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So one of my first projects with WMS/HEC-RAS involves an entire river system, with multiple lakes and dams along the entire system. I understand how to bring cross-sections and dams from WMS to HEC-RAS. However, how do I model the lakes that the dams actually hold back?

My basic understanding of these two programs shows that on HEC-RAS I can model Storage areas, and I can connect the Areas to a certain cross-section. Can I place a connection for a storage area (aka my lake) on the cross-section that drains into the lake, and then another connection on the cross-section that models my dam?

Also, if I model a storage area on HEC-RAS, what will read back into WMS? Will it work?

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Nick,

WMS can be used to define your basic HEC-RAS model with cross sections and stream centerlines. After this has been defined, you can export your model to HEC-RAS and define other structures such as storage areas. Storage areas cannot be defined directly in WMS at this time. After the RAS model is finished, WMS reads the water surface elevations from HEC-RAS which can be used to delineate the floodplain. We are open to suggestions on anything that could be improved in the HEC-RAS interface.

Chris

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Chris,

Thanks for the reply. I believe what WMS does is fine. I was jsut hoping that it could possibly do more, but I don't think it could even if it wanted too due to HEC-RAS limitations. I am just wishing HEC0RAS allowed you to model Lakes and Ponds In-Line with the river. I will have to look at HEC-RAS more.

On another side note, does HEC-HMS or any other program let you define lakes/ponds in-line with the river, and do dam breach routing for flood inundation maps, then import back into WMS? I am still trying to learn the best way to model what I need....

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Nick,

I'm not sure exactly what you're trying to do, but you should be able to define a dam break simulation in HEC-RAS and read the solution into WMS. The solution will be an unsteady solution, so there will be multiple time steps. WMS allows you to delineate the flood at each of these time steps so you can define an inundation map. We don't have a tutorial for doing this, though we would like to make a tutorial at some point.

Chris

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I will try to be more exact. Here's an example:

I have a dam that is currently impounding a lake. The 1st lake runs into a 1st river reach, which runs into a 2nd lake. The 2nd lake is also impounded by a dam, which runs into a 2nd river reach. The 2nd river reach runs to a 3rd lake.

I know it is easy to model the 1st lake, dam, and river reach. However, HEC-RAS seems to not want to add a second lake, unless I want to end on that lake. Basically, I can only have a lake, then river, then lake, and nothing more. If I want to add a lake in between these two lakes, I need to model it as a storage area, which does not seem correct, hydrologically.

So, it seems I would have to split this up into two models, and use flow results from the first model to help model the second model. Does this make more sense? Am I correct or wrong in my assumptions?

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