The $30-$year average flow for a river is $13,400$ cfs with standard deviation of $2,410.$ a$.$ What would be a $100$year peak flow? b$.$ What would be the normal depth in a trapezoidal channel that would handle this flow, assuming Manning$$s roughness coefficient of $0\mathrm{.}022,$ bottom width of $100$ ft$,$ side slope of $1($V$)$:$3($H$)$ and channel slope of $2\%.$ c$.$ What is the critical depth in this channel? d$.$ What should be the bottom width, if the water depth in channel cannot exceed $4$ ft$?$