[cameron]

If you go to the profile output options, there is a “Standard Table # Decimals” option where you can add more precision.

[cameron]

If you post your model I will try and take a look at what is going on.

[cameron]

Do you have any nearby gages that have hydrograph data? If so you could just pick representative event and use a multiplier for your peak flows.

Are there any studies of nearby streams that have a hydrograph? You could use that with a multiplier.

You could also just create a single basin hydrology model and calibrate the lag time and CN value to match your peak flow.

you could also just run the 2D model with a constant flow of your peak and simulate a “Steady State” scenario.

[cameron]

What are you trying to do with the buildings? Use them for Manning’s? Use them as mesh refinement regions?

I would not recommend loading in 41000 building footprints as Mapper will just be extremely slow if they all load at all. I have loaded in thousands and thousands of polygons before, but I ended up reducing it down to only the buildings that would significantly impact the results.

I have also just burned the buildings into the terrain which worked pretty well.

[cameron]

Is this based on only one inflow or do you have multiple inflows? Did you set a minimum flow value or multiplier for your inflow? Are your inflow hydrographs correct (values and time interval)? Are your reach lengths set correctly? Is there any detention that would reduce the flows down?

[cameron]

If you want the Vx and Vy, you have to check a box in HEC-RAS output options (HDF5 output) to have it store them in the *.hdf file.

There is an option in HEC-RAS Mapper to set create vector arrows or do particle tracing, but not a way to export the vectors themselves.

What I have done is used the data from the *.hdf and created the vectors in GIS.

[cameron]

your model is going unstable. This could be due to a lot of things. What is your time step? Did you turn on the 1D/2D iteration option? What happens if you switch to the full momentum solver?

[cameron]

You could model the culvert/bridge as cross-sections with lids. If the water surface will never touch the low chord, then you could just ignore the culvert/bridge and just use cross-sections making sure to take into account roughness changes.

As for culvert entrance losses, the manual provides different values based on different types of configurations. In reality, you should try and calibrate the losses based on actual flow data, but this does not happen often as there is usually no data.

It is up to the modeler to decide if what they see in HEC-RAS is too much entrance loss or not and adjust as needed. This could be done by checking culvert losses in HY-8, culvert nomographs, hand calculations, or other software.

[cameron]

I usually use breaklines either along the banks or one down the center of the channel. There is other software that can create meshes for HEC-RAS which have better meshing options and you can orient the cells.

[cameron]

I would lower the roughness values for the channel to something more reasonable. I would reduce the cell size near the channel so you have at least 2 cells across the channel.

If you perform adjust the downstream boundary condition does it impact the results significantly?

I was just making sure that the terrain you are using picks up the channel inverts and not just based on LiDAR which would have the wse elevation and not the inverts.

If you cut a cross-section at the location of the gage and do a simple manning’s calculation on the capacity for a few different discharges, does the wse match the gage?

Does the gage datum match the vertical datum of your terrain?

[cameron]

I always recommend this. This is a common practice with other 2D software.

[cameron]

What is your roughness values? Is the water contained in the channel at all of the flows or is there flooding in the overbanks? Are you using the full momentum or diffusion wave solver? What is your cell size? How close is this location to one of your boundary conditions? It appears the comparison gets closer at higher flows, are you picking up the channel bathymetry correctly for low flows?

[cameron]

The code doesn’t help.

The program is usually pretty stable as long as the time step is reasonable for an all 2D model. Do you have any culverts or other hydraulic structures in your 2D model?

If you are getting a lot of iteration error messages when running it in full momentum, I would check to see where those are occurring and adjust the cells.

Not sure what time step you are using or your cell size but try going smaller on the time step.

[cameron]

That error code is not useful as it is basically saying it is just crashing.

My guess is that the 1D portion of your model is going unstable causing odd results. If the 1D channel is quite different, make sure ineffective flow areas are set correctly, maybe add some interpolated cross-sections to see if that fixes the issue.

Do you have the 1D/2D iterations turned on?

Are the weir coefficients for your lateral structure reasonable?

[cameron]

In the Template Design you can check a box that says Fill Channel Below Template which should do what you want.

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