[cameron]

Is it failing at a wse elevation or a time? If at a wse elevation, does the model results reach that elevation?

[cameron]

The answer is simple. Do everything in Stateplane and then convert the final floodplain and results to the DSOD required projection.

[cameron]

You can have cross-sections in expansion/contraction reaches, you just have to make sure the ineffective areas are added to them correctly.

I generally only use interpolated cross-sections in unsteady models to help with stability. Real data if available should be used over interpolated cross-sections almost always.

[cameron]

There is an option to set the bank stations to the wse elevation. So run the 10 year flows, use this option and you should be good to go with any other flow.

[cameron]

The issue with allowing one person to get away with 0.02 ft is probably not a big deal, but if multiple people do studies in the same system allowing 0.02 ft then eventually you would get above the 0.1 or 0.5 ft and we would never know as everyone says it is negligible.

The idea of comparing existing to proposed is supposed to wash out any error in accuracy as equal error would be occurring to both simulations.

One thing that is important to note is the version of HEC-RAS you are using. If you took a model from version 4.1 and ran it in version 5.0.5, the results at bridges would be quite different.

[cameron]

the plan hdf files are what contain most of the results and are the most important files to to copy over.

To copy the dss data, you need to open them in DSSVue and copy into one of them.

[cameron]

The accuracy is something you set in the control parameters. You specify a tolerance for the wse that it has to meet for it to stop iterating and move on to the next time step. If it can’t meet the tolerance you set in the number of iterations you specify, it spits out the error for that time step which would be the accuracy. This does not account for the hydrology or terrain accuracy. Garbage in equals garbage out.

[cameron]

if you have the three plans in one HEC-RAS model. you can make copies of the folder run each run on a different machine, and then copy the outputs to one of the folders and everything should be there except for data that is stored in the dss file which will also need to be copied to a single dss file

[cameron]

What is the water surface profile comparison between the two solvers? I have found that for some models, the FM solver will add extra losses that don’t make sense. Just by switching between the two solvers, the wse changed over 12 ft at a USGS gage location for one study. The DW solver was within 1 ft of the gage and the FM was 12 ft too high.

My guess is that the FM profile is higher which makes the model more stable and gives less 1D/2D iterations so it runs faster. Is it correct is something you will have to check. I recommend doing side calculations to verify it is working correctly.

[cameron]

There is a 2D manual that comes with the software that explains how to do this.

[cameron]

if it is a all 2D model then it should be really small (0.1% is reasonable) as it is a finite volume model. Once you add in 1D cross-sections the chance the volume error goes up increases and a higher volume error can be acceptable.

[cameron]

besides what Jarvus has said, I have also found that the diffusion wave solver gives way more stable results than full momentum for 2D culverts.

[cameron]

That could possibly help. not sure how long the lateral structures are, but you could set them to 2D equation instead of weir and see if that helps.

[cameron]

The link below has projection files you can download or you can create them in ArcMap or QGIS

http://spatialreference.org/

[cameron]

you would need to set the gate with GIS coordinates as it is really long. You would need to delete the culvert as well.

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