Wrongly calculated critical depth.

[DEANSON]

I have some questions about theory behind HEC-RAS.
When run the stead flow, we can choose the computation method for critical depth calculation.
Then if we choose the parabolic, it seems that it has more rapid rating curve than the one gotten from multiple method.

Red line stands for multiple method and blue one is for parabolic

Why it happened?
Furthermore, if we wrongly calculate the critical depth and specific energy, what things would cause consequently?
Thank you

[Author]

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