The larger the roughness coefficient of the Manning "n" value indicates what about the flow velocity?

• A. Faster
• B. Slower
• C. Uniform
• D. Steady

Answer: (B)

The roughness coefficient, represented by Manning's "n" value, is a key factor in determining the flow velocity of water in open channels. A larger roughness coefficient signifies a greater degree of roughness along the channel bed and banks, which increases resistance to the flow of water.

As resistance increases due to higher roughness, the velocity of the water flow decreases. This means that with a higher "n" value, water encounters more friction and turbulence, leading to a slower flow velocity. Understanding this relationship is essential in hydraulic design and analysis, as it allows engineers to predict how water will behave in various channel conditions and plan accordingly based on the expected flow rates.