This command uses the same Manning's equations as non-erodible channel design. In this case, the discharge and velocity are known. The velocity must be less than a maximum to prevent erosion. The program calculates the channel dimensions that meet the requirements.
First choose the channel and water type. Then either enter the Manning's n, velocity, and tractive force or select them from a table of channel types by clicking Select from Table. Also fill in the slope and discharge. Finally, choose either Calc Base or Calc Ratios to compute the channel dimensions. The Standard Parameters are used in drawing the channel detail. When OK is selected, the routine ends and the channel is drawn if Draw Channel Detail is checked.
When choosing Calc Base or Calc Ratios, there will be a message Error: unable to solve these parameters on the top line if the design parameters never reach erosion conditions for any channel dimension. Consider an extreme error case with a discharge of 1 cfs, a slope of 0.1%, and a velocity of 5.0 fps. There are no dimensions that meet these requirements. So, for this case, the channel dimensions can be set anyway to avoid erosion.
Pulldown Menu Location: Structure in Hydrology
Keyboard Command: channel2
Prerequisite: None
File Names: \lsp\chan_erd.lsp, \lsp\hydro.dcl