HEC RAS unsteady flow adding storage area 1

[waterwitch]

I am trying to run a dambreach model and need to attach a storage area to the upstream end of reach/cross section.

I have a sample problem that is already set up that way. The storage area editor shows a storage area - cross section connection.
I have tried several colleagues and no seems to know how to do it.

Any ideas?

 

[Drew08]

You can't connect a storage area directly to a cross-section. You need to route it through a lateral structure. This makes sense; something needs to define the rate of inflow/outflow from the storage area.

I assume you’re trying to do a level-pool breach routing, i.e. the storage area defines the breached reservoir. HEC-RAS is river model designed for dynamic pool routing where the reservoir is defined using cross-sections. One way around this is to create a "dummy" dam immediately downstream from the real dam. The "dummy" dam is a lateral levee that connects the storage area to the channel, and is the one that is set to breach. The real dam, defined in the stream channel, is merely there to prevent upstream flow.

If this technique isn't acceptable, and you must do level pool routing, your next option would be BOSS DAMBRK. But DAMBRK is a rather pricy proprietary program. Another option would be to set up the reservoir in HEC-HMS, perform the dam breach, and import the resulting breach hydrograph to HEC-RAS as the upstream inflow hydrograph. Only define the channel downstream of the dam. The breach methodology is the same in both programs.

 

[waterwitch]

Usually, I run the dambreach using multiple sections through the reservoir. However, I cannot get the program to run so I am trying the level pool option.

I have a working sample model where the SA is connected to the reach..(no lateral structure) When I asked the individual that set up the model..he said that he thought he dragged the reach to the SA. I tried that ..it didn't work
now I guess I'll try adding points to a reach and see if I can drag it to the SA.
I usually run the DAMBRK model but my client wants this one in HEC RAS so they can graphically see the dam breach.
I will attach the model where the area is at the top..see if you can figure it out.

Thank you so much for your reply!

 

[DamEng1]

HEC-RAS seems to have a glitch in this area. You have to create the storage area first in your geometry and then create the reach and HEC-RAS will prompt you to connect the two.

 

[waterwitch]

Thank you so much!

 

[waterwitch]

DamEng1.................My actual project is already entered as a steadyflow tributary with several cross sections, culverts, etc. Is there a way to start a new geometry with the storage area..then add the large cross section reach file to the new geometry ? Could it be accomplished by adding points to a reach in some manner?

 

[DamEng1]

I just recently got HEC-RAS to work with an existing reach by going to the edit menu and selecting move object and moving the center of the storage area over the upstream node of the reach and then clicking that upstream node and it gave me the prompt.

 

[waterwitch]

I selected move object and moved the center of the storage area over the upstream node and did the following:

rt clicked node..nothing
lft clicked node..nothing

unchecked the move object and then clicked the node..also nothing

am I missing a step?

 

[DamEng1]

Be sure and move the black and white center point directly over the node and just left click. I am using HEC-RAS 4.0 and it has worked multiple times.

 

[waterwitch]

You ROCK!!!!!!!!!!!!!!!!!!!!!!!!

I cannot thank you enough. While I have been trying to make this work, I have started entering info into HEC-HMS in order to create a breach hydrograph which I will import into my HEC RAS model incase the HEC RAS dambreach doesn't work.

I have entered all the information for the reservoir node but the dambreach icon is not coming up...any suggestions?

 

[DamEng1]

Sorry but I don't, I have very little experience with HMS and stray away from it as much as possible. It still has lots of bugs and little kinks that are a pain to deal with.

 

[waterwitch]

I cannot thank you enough for your help!