A super drainage system and a method for flood control comprise an open channel, a reinforced concrete conduit (RCC) inside the open channel. The RCC has a bottom slab supported on a riverbed, a bank-side wall for retaining bank soils, and a top slab elevated above a predetermined level. The RCC supports a road below the top of river banks for traffic traveling along the river banks during normal weather conditions. The traffic is either on the top slab or on the bottom slab. During extreme weather conditions, traffic is evacuated from the super drainage system and the entire space is available for water conveyance.