Briefing: Surface water capture for higher intensity storms

As drainage systems are required to accommodate the flows and volumes attributable to higher storm return events, the surface water capture systems need to deliver these flows. Therefore, if a piped system is designed for a 1:30 year 15 min storm, the surface water capture system will need to be designed for at least a 1:5 year 5 min storm to ensure that sufficient flow is captured and conveyed into the system. This note is to raise awareness of the need to consider how drainage systems need to capture as well as convey surface water run-off.