Water Surface Profiles

[drainage321]

I had the x-section blog posts earlier – please refer to those for a graphical representation of the model.

Is it out of the question to have water surface profiles “jump” around periodically when evaluating 499 different profiles (2 yr through 500 yr)? If i look at some of the main events – the profiles look good but when looking at a simulation of all 499 profiles – it is pretty jumpy.

I had to raise the ineffective area elevations higher than i would have expected to even get them this linear.

[Chris G.]

some of that is bound to happen around structures, especially when one profile may be low flow, and the next pressure flow. Or pressure flow to pressure and weir flow. Switching between equations (which is what RAS does when switching between these regimes at bridges) can cause some overlapping of profiles just upstream of the structure.

This can also happen when ineffective flow areas are just “overtopped” and turn off. Again, this should be a local phenomenon.

Sometimes, it’s numerical instability. I suggest plot critical depth and see if you are defaulting to critical depth as some of the “jumpy” areas. You may need more cross sections, or better cross sections in these areas.

Good Luck-
Chris
@RASModel

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