Finding Channel Height, Channel Width, and Velocity of Water
By Chris Russell
This worksheet will:
Calculate the height, width, and velocity of water in a trapezoidal channel
Apply to hydraulics and civil engineering
Perform using flow rate, Manning Coefficient, Mesa County SWMM Manual, iterative guess, slope, etc.
This worksheet using PTC Mathcad models the low water crossing geometry as a trapezoid to find the height, width, and velocity of the water in a channel.
First, the worksheet lays out the different components of the calculation including flow rate in CFS, the Manning Coefficient, Slope, the channel bank angle, the width of the channel bottom in feet, and the depth of the channel in feet using an iterative guess.
It then sets up the different formulas to find the depth of the channel at the specific flow rate, the width of the channel at the specific flow rate, and the river velocity in feet per second. It then directs you to the confirmation of results in HEC-14, Table III-1 in the Mesa County SWMM Manual, I-16.
All notation, formulas, calculations, and solutions, have been provided to help you in your own calculations.