Mask definition and boundary condition/value.

[Sindre Eikenes]

Hi,

I've created a couple of maps in the Bergen (Norway) area which are starting to look promising. I do however have some issues regarding the boundary conditions type, value and mask. 

First of all, by looking at the maps below one can see that the water is overflowing way too much in the areas surrounding the outlet areas (the ocean and a smaller lake innland), as shown in a red outline color. As of now these areas have not been masked out, but rather specified as a outlet-line in bctype and bcvalue. So my question is if I should mask out these areas so that the water won't accumulate around them.

The next question is related to the boundary condition types and values. I have used bctype number 4 (User-defined water depth inside the domain) and bcvalue as 0 (as in 0 water depth). Is there another bctype which would be a better choice? I believe that a condition type where all the water leave the domain without accumulating would be better, but I can not seem to figure out which one that would be. 

* All of the maps below are the same area. The top one is showing most of the watershed including the (red) outlet lines. The one in the show water depth and the one at the bottom show velocity. These two latter ones are recorded at a time step with 13,1 mm precipitation. 

Best regards,

Sindre

[Laurent C.]

Hi Sindre,

For a coastline, I would suggest:

- Masking most of the body of water, leaving out just a one-cell wide buffer.

- Setting the boundary condition type to 4 and the value to 0 or another relevant height to account for tides, for example.

In your case, from the look of your maps, it seems your model is suffering from some numerical instabilities. Have a look at the statistics file to confirm, especially the "created_vol" and "%error". Those should be close to zero. If confirm, I suggest you have a look at the manual page on instabilities:

https://itzi.readthedocs.io/en/latest/faq.html#controlling-numerical-instabilities

Regards,

Laurent

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