Flow Rate Characteristics

Flow rate is calculated using the HR Wallingford method as recommended by the Highways Agency. The equation has an in-built safety factor to allow for the inevitable silt and debris to build up, ensuring that the unit continues to work between maintenance cycles.

The graph provides a guide to the size of unit necessary to achieve a required flow. The calculations are based on a 1000m² area 100m long and 1 outlet utilising a 100mm channel depth.

Fowler & Holden Ltd will carry out flow rate calculations on behalf of designers and contractors. With climate change and increased storm rainfall levels the performance of drainage schemes has become a crucial factor in ensuring safety for road users.

FastFlow is manufactured to a size that matches bridge deck configuration and flow rate requirements giving designers ultimate flexibility on the depth and width of the unit specified.

Units can be supplied either half batter or 45° splay..


"We also provide bespoke engineering solutions. Visit the Fowler & Holden website for more details."