Head Required for Open Channel

[Trackfiend]

How would you calculate what is the head required to drive flow at 6 ft/s thru an open rectangular channel (5 ft wide and 15 ft deep), that has zero slope and that is approximately 90 ft in length?

 

[cvg]

depends on how much flow you have. velocity and head vary widely with the depth of flow in the channel. use mannings equation and the friction slope as the longitudinal slope in the equation

 

[chicopee]

How is the water to be introduced in the channel with zero slope and how is the water leaving the channel--weir, dam...?

 

[Trackfiend]

Upstream of this concrete channel is a man-made canal. The water from the man-made canal flows into a by-pass culvert. This culvert discharges into the concrete channel. I'm attempting to use EPA's SWMM but so far I keep surcharging the upstream end.

If I were to use manning's equation, would I have to solve for R? That doesn't seem to give an answer for what type of head is needed on the upstream end to maintain a velocity of 6 ft/s in the downstream concrete channel.

 

[Trackfiend]

Sorry for the lack of info and details on the problem at hand (info being received from a project manager over the weekend) but after talking with him this morning, it seems that the problem is much more complicated than what I was led to believe, but I now have more information (flow rate, upstream and downstream channel cross-sections, invert elevations, etc.). I'm going to model this in HEC-RAS (steady flow simulation) and see if I can't carve up a solution. Thanks for the replies.