What is the recommended coefficient of roughness value for storm drains of all sizes?

The recommended coefficient of roughness for storm drains of all sizes is typically 0.0145. This value is based on established hydraulic engineering practices and is important for accurately calculating flow conditions in stormwater drainage systems.

Using the proper coefficient of roughness is crucial because it affects the flow velocity and flow rate estimates for storm drains. The 0.0145 coefficient reflects a typical condition for smooth materials commonly used in storm drain construction, such as concrete or PVC, which provides a reliable basis for hydraulic calculations.

When designing stormwater systems, engineers need to ensure that they account for the roughness of the surfaces in order to predict how the water will travel through the drain effectively. Selecting the correct coefficient is also vital for meeting applicable codes and standards related to drainage performance.