Traditional Drainage Systems
Traditional building drainage systems are designed solely for conveyance — moving rainwater off the roof and into the municipal drainage network as quickly as possible. They consist of roof drains, internal downpipes or external gutters, and connections to the building sewer or stormwater pipe.
These systems are entirely passive: they provide no detention, no flow control, and no monitoring. Their design is governed by plumbing codes that specify minimum pipe sizes based on roof area and local rainfall intensity. They work reliably for their intended purpose (roof drainage) but contribute to the urban stormwater problem by delivering peak flows to the municipal system without attenuation.
Traditional drainage remains appropriate for buildings where stormwater management is not required by regulation and where the municipal drainage system has adequate capacity. For buildings subject to stormwater retention requirements or in areas with constrained drainage infrastructure, additional measures are necessary.
Blue Roof Systems
Blue roof systems add a detention function to the rooftop by using flow restrictors, weirs, or barriers at drainage outlets to hold rainwater temporarily. The retained water drains slowly through a calibrated orifice or controlled valve after the rain event subsides.
Passive blue roofs use fixed orifice restrictors — the release rate is set at installation and does not change. Active blue roofs replace the fixed orifice with a motorised valve that can adjust the release rate in response to real-time conditions. Active systems provide greater flexibility but require power, communication, and a control system.
Blue roofs are well suited to flat commercial rooftops with adequate structural capacity. They add relatively little weight compared to green roofs (no soil or vegetation), and they are compatible with standard waterproofing membranes rated for ponding. Their primary limitation is that passive versions cannot adapt to varying conditions, and all versions require clear overflow provisions for events exceeding design capacity.
Retention Tank Systems
Retention tanks store stormwater in dedicated vessels — either below grade (underground tanks or cisterns) or above grade (on-site storage structures). Stored water can be released to the drainage system after peak flows subside, or reused for non-potable purposes such as irrigation, toilet flushing, or cooling system make-up.
Retention tanks offer significant storage volume and can be sized for large design events. They are effective in managing both peak flow (by detaining runoff) and total volume (by enabling reuse). However, they require substantial space, structural support (particularly for below-grade installations), regular maintenance (sediment removal, pump inspection), and additional plumbing for reuse applications.
Tank systems are most common in large commercial developments, institutional campuses, and projects where water reuse provides an economic return. For individual buildings seeking primarily peak flow reduction, rooftop detention (blue roof) systems are often more practical and cost-effective.
Smart Stormwater Monitoring Platforms
Smart stormwater monitoring platforms represent the integration of digital technology with physical stormwater infrastructure. These platforms typically include sensors (water depth, flow rate, rainfall), actuated flow control devices (motorised valves), communication infrastructure (cellular, Wi-Fi, or wired), and cloud-based software for monitoring, configuration, and reporting.
SmartFlow is an example of a smart stormwater monitoring and control platform designed specifically for buildings. It combines a compact rooftop hardware unit with a cloud dashboard that provides real-time visibility across multiple sites. The platform uses weather forecast data and real-time sensor readings to optimise valve positions, balancing stormwater retention against structural safety constraints.
The advantages of smart platforms over passive systems include adaptive response to varying rainfall conditions, remote monitoring without site visits, documented performance data for regulatory compliance, and the potential for coordinated operation across multiple buildings in a catchment.
Smart platforms are most appropriate where active stormwater management is required by regulation or where building operators need quantified performance data. The technology adds cost compared to passive systems but provides capabilities that passive approaches cannot match.