Hello Russel,

thanks for your response and the reference.
I fully agree that this is an very old issue and that
measurements/studies have been carried out exactly on this topic (btw.
you can access the report you have quoted online under :
http://www.engr.utk.edu/hydraulics/openchannels/Index.html).

I just wonder, how many of us really take the values straight from any
kind of resource and have immediately the best fitting parameter set
without having to calibrate? My small experience tells me it happens
very, very rarely and then very often to very experienced users.
Therefore, I am interested in your personal, practical experience.

Florian Pappenberger
f.pappenberger@lancaster.ac.uk