Example $6\mathrm{.}1$

A $3-$m$-$wide rectangular irrigation channel carries a discharge of $25\mathrm{.}3\frac{m^3}{sec}$ at a uniform depth of $1\mathrm{.}2m.$ Determine the slope of the channel if Manning's coefficient is $n=0\mathrm{.}022.$

Example $6\mathrm{.}3$

If the discharge in the channel in Example $6\mathrm{.}1$ is increased to $40\frac{m^3}{sec},$ what is the normal depth of the flow?

$\frac{?}{\text{b}\text{a}\text{r}}($ Classroom Computer Exercise$-$Normal Depth $)$ in Open Channels

Review Example $6\mathrm{.}3.$ Obtain or write software appropriate for solving normal depth in open channels. $($See the note at the end of Example $6\mathrm{.}3$ and the book's preface for suggestions.$)$ Answer the following questions by performing a computer analysis of the open channel described in Example $6\mathrm{.}3$ and its modifications.

$($a$)$ Before using the software, what data do you anticipate it will need to compute normal depth for the channel in Example $6\mathrm{.}3?$

$($b$)$ Now enter the data requested by the software and perform a normal depth analysis. Compare your computer result with the answer listed for Example $6\mathrm{.}3.$ Is there any discrepancy? Comments?

$($c$)$ What would happen to the flow rate in the channel if the depth was unchanged but the bottom slope was doubled? Estimate the magnitude of the change. Double the slope and perform a new analysis on the computer. Did you reason correctly? Now restore the slope and flow rate to their original values.

$($d$)$ What would happen to the flow depth if the flow rate remained unchanged but the channel was lined with concrete $)=(0\mathrm{.}013?$ Estimate the magnitude of the depth change. Change the roughness value and perform a new normal depth analysis on your computer. Did you reason correctly? Now restore the roughness and flow depth to their original value.

$($e$)$ Trapezoidal geometry is necessary if a channel is unlined. $[$For bank stability, the side slopes may be limited to $1(V)$:$3(H).]$ Because of easement requirements, the unlined channel $)=(0\mathrm{.}022$ will be cheaper if the top width does not exceed $6m.$ Using the computer software, determine the top width of the channel assuming the bottom width remains $3m$ and the discharge remains $40\frac{m^3}{sec}.$ Also, determine the side slope that would produce a top width that is exactly $6m.$

$($f$)$ Is it possible to design a triangular channel with the software? Explain.

$($g$)$ Perform any other changes your instructor requests.

solve $($a$)$ through $($f$)$ please