A rectangular channel with a width of $500$ cm $,$ slope of $1$ in $100$ and a Manning's

coefficient of $0\mathrm{.}012$ has a discharge of $20000\frac{l}{s}.$ Calculate the:

$3\mathrm{.}1$ Normal depth.

$3\mathrm{.}2$ Froude number at the normal depth.

$3\mathrm{.}3$ Critical depth.

$[14$ MARKS$]$

QUESTION $4$

$4\mathrm{.}1$ Differentiate between four sewer collection systems.