Connecting 2D flow areas.

[Joe S.]

do to a terrain drop below the dam from elevation 1330 to a river channel at elevation 1240, or 90 ft drop, I was trying to develop 2 or more 2D areas. Each area is 40 ft mesh. this might help with the 2D initial startup elevation too.

referring to the Manual 5, page 5-59, there is some discussion. (1) drew a SA/SD BC line along the boundary of the 2D Areas. Does the area boundary need to overlap, or can there be an offset?

(2) draw break line Area A>B. Then edit breakline cell spacing to 20 ft. Convert breakline into new internal SA/2D Area conn. then force mesh recomputation. and enforce selected breaklines

(3) Open SA/SD area connector that was just created. Copy the terrain profile (X,Y) data to the Weir Embankment (storage area connection). Leave structure type “Weir”.

(4) adjusted the HTAB elevation and max flow rate. Connections 2D flow area A to B.

(5) before running the file, OPTIONS: adjust the upper 2D area (Area A) with 4 hours initial time. I understand we can use 2 to 4 hours. Left the initial default ramp up fraction at 0.1. Set max iterations 1D/2D to max of 20. Leave equation set as Diffusion Wave”, since modeling dam without failure case.

When running model, this error occurs. How could I adjust the weir elevation higher, to remove that error message? I cannot adjust the terrain cell elevations; without special software.

ERROR with Connection
The SA 2D Connection at Area A>B
has a weir elevation lower than the cells they are connected to
for 2D Area Area A
This is not allowed in HEC-RAS:

[Anonymous]

You can, actually, adjust the terrain without special software.

http://hecrasmodel.blogspot.com/2018/08/terrain-modification-and-direct.html

[Author]

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