[cameron]

What type of weir coefficients were you using? The weir coefficient can have a huge impact on how much water leaves/enters the 1D domain.

Do you get similar results with the 2D equations instead of weir coefficients?

[cameron]

You have to have a terrain to get any results that make sense in Mapper.

The program uses the interpolation surface created from cross-sections to plot the wse on the terrain. It should also use the same surface for velocity based on the slices mentioned above along with the bank lines layer in Mapper.

You can manually modify the interpolation surface by adjusting the edge line layer and recomputing the interpolation surface. You can also manually adjust the bank lines layer in Mapper as well.

[cameron]

Was this based on the weir equation or 2D equation for the lateral structures? Did you test different timesteps? Did you try leaving the 1D at one timestep and use time slices to reduce the timestep in 2D? Does the terrain include the channel data and if not, does the weir elevations match well the the elevations of the 1D cross-sections?

[cameron]

Are you using the full momentum or diffusion wave solver? I have noticed issues occasionally when using the full momentum solver where the water surface is not what I expected and does not match well with 1D solutions or simple manning’s calculations.

[cameron]

What I do when attempting to incorporate 1D channel data into my terrain is the following:
1. Make a 1D model based on survey data and call it Survey
2. Interpolate every 50 to 100 ft based on the stream centerline save it as a new geometry called survey with interp. Make sure to set breaklines between cross-sections when interpolating.
3. Make a copy of the geometry and call it LiDAR or DEM, then extract elevation data from it.
4. Make a copy of the LiDAR geometry and call it combined or something else.
5. With the Combined geometry open, I go to the graphical editor and merge/burn in the survey with interp data into the cross-section data and place bank stations based on the limits I want the new terrain to be.
6. Once all data is burned in I adjust the bank lines layer in Mapper as needed to make sure it covers the areas I want replaced.
7. I then export out the terrain data based on channel banks and combine it with the LiDAR/DEM.
8. I then view the new terrain in Mapper to see how the channel data merged with the LiDAR/DEM. In areas that look funny, I either add more cross-sections, adjust the bank stations, or adjust the bank lines and export out the data again.

[cameron]

Your timestep is way to high. You need to follow the Courant criteria and since since this is a dam break, you probably should be using the full momentum solver as well.

[cameron]

Did you try setting the lateral structure to use the 2D Equations?

A value of 1 could be too high of coefficent value. If you look at the user’s manual (page 3-50), a value of 1 would be if you had a levee/roadway that is elevated. If it is just natural ground, .11 to .55 in SIS units would be more appropriate.

[cameron]

Can you post your model somewhere?

[cameron]

Two things with your file.

First, you copied the output file text which does not work as an input file.

Second, HEC-2 uses spaces and not tabs. You will need to line up the spaces correctly. What I would do is get an example HEC-2 file and copy the spacing. There use to be some old dos programs that would help with checking the spacing, but not easy to find. Dodson and Associates has a window version you can purchase to help with this. I have not used it so not sure how well it works.

http://www.dodson-hydro.com/software/hydropro/hydropro.htm

[cameron]

Just a quick look shows that about halfway down the dat file there is some text that looks like it was taken from the pdf and not removed. Try removing the PG 5 and Start of PDF PG 6 and see what happens.

GR 18.6 2475 18.7 2480 0 0 0 0 0 0 PG 5

SB 0 1.55 2.5 0 7.85 0 78.54 0 -2 -2 START PDF PG 6

[cameron]

Did you set a pilot flow for the inline structure? Cross-sections need to stay wet and the dam will block all flow unless you have outlet works, but that flow may not be enough to be stable.

Is there a reason why the two dummy cross-sections have different invert elevations than the storage area?

Sediment transport and dam breach in the same model will be difficult to keep stable and get good results due to the high velocities and other issues. I would use the Unsteady sediment transport option rather Quasi-Unsteady.

It also may be easier to do the breach model only first and take the breach hydrograph to use in the sediment transport model.

[cameron]

I would reach out to HEC to see if they think it is a bug or not.

[cameron]

If you look at the dss data from HEC-RAS (plot option is when you select the data) does it show it in the correct units?

If you post your files, I will take a look. If not and I have time this weekend, I may test out my own dataset to see if I get the same issue.

[cameron]

I like to modify the *.rasmap file as well (along with the other text files), but I have found that Mapper does not always use the changes you you make to the rasmap file so I am extra cautious when working within that file.

[cameron]

Did you set your initial wse for the dummy cross-section?

Is the storage area elevation invert lower than the dummy cross-section invert?

Is the breach elevation lower than the dummy cross-section invert?

When does the error occur?

What is your minimum flow from your hydrograph?

[Author]

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