Flood risk management benefits

SuDS are designed to meet specific objectives and design criteria, much the same way as traditional drainage systems. SuDS components are generally volume based whereas pipe design is usually focused on conveyance.

The majority of SuDS components provide larger storage volumes than traditional drainage systems. Therefore, these systems will only become overloaded by events occurring over a longer duration, which generally means that “failure” results in less impact. With the majority of SuDS components managing water on the surface this increased visibility and attention to flood routes may also contribute to improved flood risk management, particularly during extreme rainfall.

In addition to the type of failure being very different, SuDS schemes retain and attenuate runoff for longer, while pipe based systems pass all this flow downstream. This means that areas downstream at risk of flooding receive all the water from an upstream pipe based system, but only a limited amount of water from a SuDS scheme.

Flood risk is managed by SuDS reducing the volume, frequency and flow rate of surface water runoff and during extreme events. Exceedance can be managed, with components and schemes "failing gracefully" and in many circumstances they can be visually monitored.

SuDS Drainage Exceedence