water surface elevation too high

[Anonymous]

Hi,
My student is modeling a mountain river and can’t get her measured discharge to match measured for water surface elevation for calibration. The channel is a pool-riffle system (restored) and has a gravel bed. The manning’s n has to be raised to ridiculously high to match. We are unsure what else to attempt to change to get a match. The overall slope matches measured water surface slope.

[Anonymous]

Manning’s n does not directly capture the large turbulence losses for steep high velocity streams.

If you aren’t already familiar with it, lookup Jarrett’s equation. The RAS hydraulic manual has a short section on it.

[Author]

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