Q1: Back water curve is caused if

ANS:B - pressure is due to weir in the channel

Backwater curve is caused if the friction head loss is more than the bed slope. A backwater curve occurs when the downstream flow is obstructed or slowed down, causing the water level to rise upstream. This phenomenon is often observed in rivers or channels with gradual changes in slope or obstructions. When the friction head loss, which is caused by the resistance of the fluid to flow along the channel, becomes greater than the bed slope, the flow slows down, leading to the formation of a backwater curve. Therefore, the correct statement is: Backwater curve is caused if the friction head loss is more than the bed slope.