Hec-Ras- Cliping a large HEC-RAS model to a small specific area

[PT60056]

Hello Everyone,

I have a large unsteady flow area hec-ras model. I need to clip the model for a certain specific area from the large model and use peak flows from the unsteady flow to make steady flow. Here are the areas i need help with.

1. I haven't had opportunity to run unsteady flow model. Is there anything I need to know for running the unsteady flow model? The model was received from other firm.

2. How to clip the smaller specific area from this large model?

Thank you for your help in advance.

 

[gbam]

Few questions:
1- Is this a regulatory model?
2- Why not modify specific area and run entire model? This approach can provide additional information for upstream and downstream tie-in points from hydraulic structures, especially provide opportunity in overbank storage if modifications are needed. One can report the changes based on River Stations and state no change for rest.
I would recommend using entire model unless there is a good reason not to.

 

[PT60056]

Clipping the model was suggested by the agency in charge

 

[Ekenny_G]

I'm assuming this is a 1D unsteady flow model, with cross-sections?

- First, determine the nearest cross-section upstream and downstream of your area of interest.
- Delete all the cross-sections and structures data outside of those areas (to clip the model)
- Then use known water surface elevations to apply stage-hydrograph as the upstream/downstream boundary condition;
- Apply your unsteady peak flow as 'constant flow' hydrograph and make sure it covers the duration of your simulation.

There maybe a some in between steps, but that's the gist of it.