$(2$ pts$)$ A trapezoidal channel has a bottom width of $b=9\mathrm{.}0m$ and side slopes of

$m=4.$ The channel is spanned by a bridge that is supported by three piers,

each $2$ m wide. At a design flow of $Q=30\frac{m^3}{s}$ the flow depth in the

channel is $1\mathrm{.}8$ m as it approaches the bridge section. Determine if the bridge

piers cause choking and calculate the flow depth at the bridge section.

Neglect the head loss due to the piers.

Hint: Adjust the width of the channel bottom at the bridge section by

subtracting the combined width of the $3$ piers from the bottom width $b.$