A bridge is placed in a long rectangular channel. The channel width

upstream $(\frac{u}{s})$ and downstream $(\frac{d}{s})$ from the bridge is $B=3\mathrm{.}5m.$

The flow rate in the channel is $15\frac{m^3}{s},$ the channel bed slope is

$1\%,$ and the Manning roughness coefficient is $n=0\mathrm{.}014.$

What is the critical depth $\frac{u}{s}$ from the bridge?

What is the $\frac{u}{s}$ channel's normal depth? Is it subcritical or

supercritical flow?

What is the minimum channel width such that the $\frac{u}{s}WL$ is

not influenced for this discharge?