a A river exits its catchment area through a narrow canyon, spanned by a bridge. The river has a mainstream length L = 5 km, slope of 5.4 m/km and catchment area of 8.5 km². The rain intensity was 140 mm/h, with the run-off coefficient of 0.32. Find the peak flow rate of the river as it exits the catchment area. (12 marks) b) If the canyon beneath this bridge is approximated by a rectangular cross-section of width 3 m and height 30 m, will the water overflow the bridge when the peak flow rate is reached? Assume that the Manning roughness coefficient is 0.05 and hydraulic radius at the peak flow rate is equal to 1.5 m. (13 marks)
