What is the maximum flow velocity allowed in a grass channel during a 1 inch storm event?

The maximum flow velocity allowed in a grass channel during a 1-inch storm event is established to prevent the erosion of the channel and to ensure that the grass can effectively filter and manage stormwater. A flow velocity of 1 ft/sec is considered suitable because it is slow enough to minimize erosion and allow for sediment deposition, while still providing efficient water conveyance.

Grass channels are designed to handle stormwater flows while promoting infiltration and filtration. Excessively high velocities can lead to scour and damage to the vegetation established within the channel, hindering its functionality as a stormwater control measure. Therefore, 1 ft/sec strikes a balance between effective drainage capacity and the protection of the channel ecosystem.

Higher velocities would increase the risk of erosion and reduce the channel's longevity and effectiveness, while velocities too low may not be adequate to move stormwater efficiently. Thus, 1 ft/sec is recognized as the maximum permissible flow velocity that aligns with best management practices for grass channels during typical rainfall events.