ABG, a UK drainage specialist, developed SuDS Blueroof, a system to mimic natural drainage and attenuate stormwater to alleviate hydraulic impact on downstream flood risk. It is a temporary void storage of rainwater above ground level or on a roof or podium with no underground tanks. The water can be released in a controlled manner to allow and manage a timely discharge and not overload the downstream drainage system. ABG designs and retrofits cellular water holders and a special restrictor chamber to regulate this outflow over a designated period, limiting downstream flooding risk.