Hi
I’m new to HEC-RAS and I’d like to ask a simple question about the different results between HEC-RAS and the use of the simple Mannings equation for a single cross-section of a prismatic channel (somethig like this http://uon.sdsu.edu/onlinechannel02.php).
I have made a HecRas model of a mountanous torrent with slope 3 %. I tried to compare the discharge for the same cross-section using similar parameters. I don’t expect to get the same results, but at least similar ones. I noticed that Hec Ras “unterestimates” the results of the simple Mannings equation for a single cross-section, almost 60 m3/s in same cases too. Is there any explenation for this?
Best regards