Conceptual Question about Cross Sectional Area / WSEL 1

[sabz04]

Hi,

I am trying to understand a result I am getting, that I think defies logic, but maybe I am thinking about it incorrectly. Basically, I am looking at hydraulic effects (using HEC-RAS) on a cross section before and after extracting from it. The cross sectional area at the cross section is increasing. Nothing else has been changed in the model (no other cross sections, Manning's values, Reach lengths, etc.). Therefore, I would think since there is more area for water to flow through, the WSEL would decrease. However, it does just the opposite, and I am stumped. Does anyone have any idea why this could be occuring?

Thanks!

 

[francesca]

Water slows down, lower velocity head = higher WSE.

 

[sabz04]

Thanks, Francesca. That was simple. I was overlooking the basic concepts! I appreciate your response.

 

[cvg]

three things are changing, not just one

area
wetted perimeter
hydraulic radius