ANS:B - head loss due to friction in open channels

Manning's formula is used for flow in open channels. Manning's formula, also known as the Manning equation, is an empirical formula used to estimate the velocity, discharge, and flow depth in open channel flow, such as rivers, streams, canals, and irrigation ditches. It relates the flow rate to the channel geometry, roughness coefficient, and hydraulic gradient. The formula is expressed as: Q=n1​AR2/3S1/2 Where:

• Q is the discharge (flow rate),
• n is Manning's roughness coefficient,
• A is the cross-sectional area of flow,
• R is the hydraulic radius, and
• S is the slope of the channel.