Example $(4)$

A trapezoidal concrete$-$lined channel

$-$a constant bed slope of $0\mathrm{.}0015,$

a bed width of $3m$ and

$-$side slopes $1$:$1$

$-n=0\mathrm{.}017$

A control gate increased the depth immediately upstream to $4\mathrm{.}0m$ when the discharge is $19\frac{m^3}{s}.$ Calculate the distance between gate point and the point in which water depth of $3\mathrm{.}8m,$ using $0\mathrm{.}1m$ increments.

From manning Eqn. $y_0=1\mathrm{.}75m$

From Froude number $y_c=1\mathrm{.}36m$

$y_0>y_{c}Ml$

$\backslash$table$[[($m$),(m^2),($m$),($m$),(\frac{m^3}{s}),(\frac{m}{s}),($m$),($m$),,,(m),($m$)],[y,$A$,$P$,$R$,$Q$,$V$,$E$,E,$Sf$,$Sfave,$x,x$