Design a concrete-lined section for a 2-km stream reach with S = 0.0025 m/m, upstream of an existing drop structure. The existing channel is approximately 55 m wide. The channel downstream of the drop structure is lined and has sufficient capacity such that the proposed lining will not impact flooding and erosion conditions in the downstream reach. Permissible velocity for concrete lining is 5.0 m/s and n = 0.015. Use the Rational Method for Q = 0.2755 CIA for 12 hours and the following additional data below: C = 0.15, catchment area = 1 sq. km., average Manning's n for Concrete-lined channel, side slope of 2h:1V, rainfall data Duration (min) Return period 10 15 30 155.08 mm/h 128.12 mm/h 88.52 mm/h 10-V