$5\mathrm{.}1$ A rectangular concrete channel, $4m$ wide, is to carry water at a flow rate of $20\frac{m^3}{s}.$

The channel slope is $0\mathrm{.}00025.$ Calculate the depth of flow.

$5\mathrm{.}2$ After a flood had passed an observation station on the Nahoon River, a technician visited

the site, and by locating flood marks, performing appropriate surveying, and doing

necessary calculations, determined that the water surface slope at the time of the peak

flooding was $0\mathrm{.}00076$ and the channel was as shown in Figure $2$ below. The technician

also noted that the channel bottom was "earth" and the floodway was with "grass and

weeds". Calculate the peak flood discharge.

Figure $2$

$($Note: drawing not to scale$)$