Stormwater from a catchment area of 17 Ha in Kingaroy is conveyed via a 1200mm wide and 700mm rectangular open channel. The drainage path length is 60 m. The head of the catchment has an elevation of RL 73.280 m AHD and the invert of the new drain has an elevation of 71.530 m AHD. The catchment area can best be described as poorly grassed surface with a surface roughness of 0.035 and having medium permeability soil. Assume that the surface water from the catchment sheet flow over the surface. Determine the time of concentration for the catchment area. Determine the peak discharge flow rate, for a 2 year ARI. Determine the longitudinal slope of the channel if the channel roughness is 0.013 and the depth of flow in the channel is 420mm when the peak discharge flow of 2 year ARI from the catchment is flowing in the channel.