Issue creating a Terrain Model of the Channel

[SwannB]

Hi,

First of all, I am doing a 1D/2D model (1D for the channel and Lateral Structures + 2D Flow Area for the floodplain).

1) I am trying to create a Terrain that include the bathymetry of the Channel with RAS MAPPER. I followed the steps from the 2D HEC RAS Mannual, but when I check the result in the “view/edit geometric data”, it appears that the terrain is not realistic at all on some part of the channel, and when I plot the Terrain in the XS data, it doesn’t match (the terrain and the XS are not overlaid).

The average distance between the XS is around 70 feet.

What could I do wrong ?

2) I am trying to include the bathymetry of the channel in the Terrain because I noticed that in some area, there is floods in RAS Mapper, but when I check in the “view XS” or “view profil” after the computation, there is no floods. So I thought that the floods shown in Ras mapper are based on the Terrain, even if I am using a 1D model in the channel. So the accurate bathymetry of my 1D model is not taken into account.
Am I right or not ?

Thank you in advance for the help that you could give me.

[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.

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