SuDS Rainwater Attenuation Sizing Chart

In the UK SuDS attenuation assessments are typically completed on a site by site basis.

The key inputs for the attenuation volume calculation is the design storm inflow and the allowable discharge rate. The design storm is location dependant and varies across the UK.  The allowable dicharge rate varies from local lead flood authority but 1 l/s appears the most common value offered by the LLFA for single residential developments.

We have completed an excercise assessing attenuation volumes for 25 sites in the UK reflecting the various water company locations.

The base design scenario assumptions are: 

• 1 in 100 year design rainfall return period
• 40% climate change
• 1 l/s allowable discharge
• FlowBrake vortex flow control
  
• Standard Rain Bloc configurations
• calculated
• 100m2 roof area
• Location as per the Water Company below

Get in touch today to complete your attenuation or soakaway sizing calc.

The table below is the sole intellectual property of Freeflush Ltd and may not be reproduced, distributed, or used without the express written permission of Freeflush Ltd. The values provided are indicative only and must not be relied upon for detailed design or specification purposes.