An asphalt pavement drains into a rectangular concrete channel. The catchment surface has an average

slope of $1\%$ and the distance from the channel boundary to the drain is $30$ m $.$ The drainage channel is $60$

m long, $20$ cm wide, $25$ cm deep and has a slope of $0\mathrm{.}6\%.$ For an effective rainfall rate of $50$mm$//$h$,$ the

flow rate in the channel is estimated to be $0\mathrm{.}02$m$3//$s$.$ Estimate the time of concentration of the

catchment. Hint: use kinematic wave based eqn $10\mathrm{.}13.$ Use Table $10\mathrm{.}1$ to determine the Manning

coefficient for asphalt pavement $($drain$)$ and for concrete $($channel$).$