[cameron]

What is the purpose of running the model for multiple years with a constant flow rate for each year? Are you doing sediment transport?

[cameron]

try reducing your 1 year outputs to something smaller.

[cameron]

try reducing your time step from 24 hours, that is a little high.

[cameron]

Try changing to the full momentum.

How many lateral structures do you have? Do any cross near bridges in the 1D?

Try switching your lateral weir to solve with the 2D solver.

How many cross-sections do you have?

[cameron]

page 6-160 of the user’s manual discusses how to import data into csv data into HEC-RAS.

[cameron]

The output represents the results at that specific time and not an average.

[cameron]

the pre-processing is always done. Your grid would have to match the DEM perfectly, not hard if you just took the coordinates of the center of each DEM cell.

I have never tried this, but would be interested to see the results.

[cameron]

could you explain more?

if you use rasters, you have to make sure they were created. If they are created and not displaying in ArcGIS, how did you load them (vrt or tif file)? How do the rasters look in RAS Mapper?

[cameron]

What is your time step? With the lateral structures, is it set to weir or 2D? Are you using the full momentum equation or the diffusion wave for the 2D solver?

[cameron]

go to where you enter the weir elevations for the weir and change the stationing to be the same as the length.

[cameron]

you need to either change the stationing of the weir or update the GIS line of the weir to be basically the same.

[cameron]

So both the upstream and downstream boundary conditions are flow hydrographs and add flow to the model? How does the water escape?

Also it sounds like you have an 1 hour time step which is way too high for a 2D model. You need to follow the guidance in HEC-RAS manual and look at the courant number.

[cameron]

The max velocity does not always occur at the peak flow. It could occur right when a cell is starting to get wet with shallow flow or it could be due to an instability. Your first figure looks like an instability.

[cameron]

What did you set for your initial condition? What I have done in the past if I want to fill up a reservoir is to add an inflow and let it run until the reservoir is at the elevation I want and then have the model write out a restart file which I use as the initial condition.

You could also break your model up into multiple 2D areas and have one of them with the initial condition.

[cameron]

Have you tried using the 2D equation instead of the weir equation for the lateral structure?

[Author]

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