Q $2$b$.$ From the discharge estimated by the Bransby Williams formula above, design an adequately sized

concrete pipe culvert to pass the $25$ years flood. The height of the road above the invert level of the river at

the culvert location is $2\mathrm{.}85m,$ the length of the culvert is $60m,$ natural streambed slope $=0\mathrm{.}01$ and the

downstream level of the $25$ years flood is $1\mathrm{.}1m$ above the downstream invert. Use a square edge with

headwall with $k_e=0\mathrm{.}2$;$k_0=1\mathrm{.}0,n$ for concrete $=0\mathrm{.}015$;$f=0\mathrm{.}02.$ You may consider multiple culverts if the

diameter of pipe becomes too big to be closer to headwater.

$20$ marks