The Tree Nurturing System (TNS™) captures and stores runoff at the kerb line, then feeds it to the root zone. The water grows the canopy that cools the street and protects the waterways downstream.
Centralised pit-and-pipe drainage is built to remove water from a single point as fast as possible. Efficient at moving water – but it disrupts the natural cycle that keeps soil, waterways and trees alive.
Traditional systems collect and convey contaminants downstream, detrimentally impacting the health and function of the receiving environment.
Where rainfall is piped away, the soils left behind are dead and barren. With the water table dropping, the soils lose oxygen, minerals and elements until they become hard and compacted.
The standardised approach commits cities to a significant end-of-line maintenance regime, alongside costly, time-consuming and insufficient manual irrigation.
Councils set canopy targets and plant to them, with each tree in a pit sized for the tree and kerbed off from the street. The runoff that would water the tree passes into the pipe instead. Although planting rates go up, the canopy those trees were planted for does not follow.
In every storm, conventional drainage drives the climate impacts that cities are fighting: degraded waterways, urban heat and lost water security.
Drainage flushes sediment and nutrients straight to receiving waters, where turbidity blocks light and smothers seagrass. TNS retains runoff at the source, reducing the volume leaving the catchment.
In Queensland, Moreton Bay's seagrass decline has been attributed largely to stormwater sediment and nutrient loads; higher sediment loads non-linearly shrink seagrass habitat.
Runoff sheets across sun-baked pavement, picks up heat, and carries it into creeks and downstream estuaries – stressing aquatic life and lowering oxygen. TNS holds runoff in cool subsurface storage and keeps it from reaching the network warm.
Runoff from hot impervious surfaces can exceed 39 °C, and overseas studies document post-storm stream-temperature surges of 7–9 °C. The extension to downstream estuaries is a recognised risk pathway, not a measured marine figure.
Draining water out of the landscape leaves no stored moisture for the evapotranspiration that cools cities, intensifying the urban heat island. TNS holds water in the soil to sustain vegetation and its cooling.
Evapotranspiration from well-watered vegetation is a core cooling mechanism in water-sensitive urban design; remove the water and you remove the cooling.
Rapid conveyance sends erosive peak flows through channels, strips groundwater recharge, and leaves streams to dry between storms – ‘urban stream syndrome’. TNS slows, stores and sinks the flow so that baseflow returns to the stream between storms.
Hydrologic ‘flashiness’ from impervious catchments drives channel erosion, habitat loss and reduced dry-weather flow – a well-documented degradation syndrome.
Rain interacting with hot, low-albedo surfaces – and the pollutants mobilised off them – may amplify downstream thermal and water-quality impacts. Source control like TNS holds that runoff in subsurface storage before it can sheet across hot pavement into the network.
The claim above is an area of active BGI research and our working hypothesis (Richards, 2023), presented as a question we're investigating and not as settled science.
All of it – the floods, the heat, the dying waterways – shows up on your street as one thing you can actually see.
Many urban street trees are planted in shallow graves, surrounded by hard, compacted engineered soils – root zones starved of water, oxygen and minerals. Declining immunity lets pathogens like phytophthora attack the cell structure, slowly and surely. Without a healthy root mass to hold the trunk and canopy, trees fail and collapse – and in many urban areas, that costs community lives.
Street trees sit in 1.8 m pits with a root barrier down the kerb and pavement edges, and a 50 mm slotted pipe for hand watering the root ball. The contractor waters them through the 12 month establishment period. After handover each tree lives on the rain that lands inside its own pit. The kerb at the edge of that pit takes the rest of the street’s runoff into the new stormwater line.
Drawn to policy, on a project with a canopy target.
Imagine a system that works like a sponge in nature. The TNS™ soaks up rainwater, cleans it, and gently releases it where it's needed most – to urban trees and plants – while letting the excess seep down to replenish groundwater. A decentralised, source-control approach: slow it, store it, sink it.
The combined systems of soil, water and vegetation – known as blue-green (living) infrastructure – moderate the release of water in heavy rainfall and provide fresh water through heatwaves. The water held in the soil supports vegetation growth, expands the tree canopy and lowers urban heat.
Unlike conventional drainage, the TNS™ is a decentralised approach in which water that infiltrates does not discharge. Retention at source is load reduction that stands without a certification argument, because the load stays on the site.
Source control reverses the logic of conveyance, slowing, storing and sinking runoff so that the system reconnects urban environments to natural hydrological processes.
Because each unit manages its own micro-catchment, the units can be arranged wide or narrow, deep or shallow, independently or connected. They can also be added, removed or rearranged to suit local space, grade and site constraints.
Ideal for retrofitting existing streets without costly excavation or redesign – adapting from dense urban streets to open landscapes while holding consistent retention and storage performance.
Both units are precast products of PPC Australia, made from a patented permeable concrete formula. The EnviroKerb Tray Inlet (ETI) sits at the kerb line, where the everyday rain runs; the fully porous EnviroKerb® unit sits downstream, taking water across the whole kerb face.
See the EnviroKerb® & ETI page →
The number of units at each node is calculated from the micro-catchment runoff calculations. From the kerb line, this is where the water goes.
Sources: kerb unit dimensions, weights and load rating – PPC Australia, brochures PPCA-BRO-001 and PPCA-BRO-002 Rev B, September 2026 (envirokerb.com.au). TNS™ hydrologic and hydraulic performance is designed and assessed against Australian Rainfall and Runoff (ARR), the national standard applying in every state. The local drainage manual applies where an authority adds its own requirements.
Everyday runoff enters the ETI at the kerb line through a tray that is sealed and removable, which keeps gross debris out of the subsurface structure.
Immediately downgradient, the EnviroKerb unit takes water across the whole porous kerb face, with no single aperture. Each unit sits over a precast water ramp that deflects water away from the pavement subgrade.
A manifold of 100 mm drainage cells directs water to modular storage tanks, sized to the design storm for the microcatchment that node serves.
From storage, water moves down through Star Water filter media within the structural soil cells, where it is available to the tree root zone. The configuration supports root mass growth and the transfer of oxygen and minerals through the profile – tree stability, tree health, canopy.
A small relief pipe at the base engages only once the connected systems have filled and the substrate is fully saturated, which an ordinary event does not reach.
Every stage terminates in storage, substrate or root zone, with a relief pipe in place of an outlet.
Each node serves the smallest practicable contributing area and holds the water from the area it serves, with none of it accumulated and conveyed.
Not a proprietary device. The TNS™ is not a stormwater quality improvement device (SQID) assessed on a manufacturer's certification – it is a culmination of established technologies forming a constructed bioretention node, and every element is modelled in MUSIC (Model for Urban Stormwater Improvement Conceptualisation) as a standard in-built node. How it is assessed →
Quality and quantity, assessed separately. Because what infiltrates doesn't discharge, the load reduction that follows from retained volume is shown as modelled in MUSIC on standard bioretention parameters. Quality obligations themselves are met by separate, appropriately certified measures. Runoff volume, frequency and peak rate are hydraulic matters, assessed in ARR the same way any detention is assessed. Neither position rests on a manufacturer's certificate or on proprietary test data.
Serviceable by design. The ARI Water Filter beneath the ETI tray protects the void structure from fines and is replaced by removal. Manifold, tanks and soil cells are geotextile-wrapped. The full maintenance case →
Materials. The elements water touches – the ETI, the EnviroKerb® unit and the water ramp – are mineral aggregate and cement as standard. The materials case →
Storage volume at each node is set by the runoff calculation for the micro-catchment it serves. The node takes water in on frequent rainfall, which carries most of the annual volume. Volume held at the source is volume that never arrives at the bottom of the catchment.
Where a site still carries conventional road drainage, that network is designed on the flows that actually reach it, modelled to Australian Rainfall and Runoff. On most layouts the pipes come down in size compared with a conventional design. The existing downstream system can often take the discharge without an upgrade. The detention basin built to hold flows back until they fit is usually no longer needed.
With the holding spread across the catchment in small units in place of one large structure at the outlet, conventional drainage stays at a reduced scale. Because what comes off a particular site depends on its rainfall, soils and layout, the reduction is quoted from the model for that catchment.
Runoff retention, distributed detention and slowing the water reduce flood risk, replenish groundwater, and protect downstream water systems – while maintaining ecosystem health.
The TNS™ is granted in Australia, China, the European Union, New Zealand and the United States, with the Indian application in late-stage examination. Patent and trade mark are held and licensed by Blue Green Infrastructure Pty Ltd. The patent covers the arrangement, and it doesn't make the node a proprietary treatment device. Every element is modelled in MUSIC as a standard in-built node.
The node is an urban green infrastructure element within the meaning of SA HB 214:2023 Urban Green Infrastructure – Planning and decision framework, a Standards Australia handbook, integrating with the blue infrastructure network in the way the handbook describes at Clause 3.3.6 – a practical bridge between policy intent and real-world implementation. Classification by variant →
Green infrastructure is an asset class under the handbook at Clause 3.3.5. The Green Infrastructure Management Manual published by the Institute of Public Works Engineering Australasia (IPWEA) sets out how such assets are registered, valued and carried in a long-term financial plan. Both documents are references for planning and managing green infrastructure, with no certification role. The TNS™ has no endorsement from Standards Australia or from IPWEA. The policy direction points the same way – the National Water Initiative, recognition of Aboriginal Peoples’ water interests, and the forthcoming National Water Agreement.
As a repeatable unit, each node lets the same arrangement scale from a single street retrofit to a whole precinct.
Each node holds the runoff from the area it serves, which reduces the flows arriving downstream. The drainage that remains is designed on what reaches it, which is ordinary hydraulic design assessed under ARR and the local drainage manual.
Matter SensAI sensors measure intake against a calibrated baseline and flag an inspection when intake drops, before a blockage forms. Maintenance then follows the data in place of a fixed schedule.
How monitoring sets the maintenance response →
EnviroKerb® · PPC Australia
The ETI and EnviroKerb unit, and the precast water ramp.
envirokerb.com.au →
ARI Water
The consumable filter element, replaced by removal at service.
ariwater.com →
Matter · watermatters.ai
Baseline intake monitoring and proactive maintenance.
watermatters.ai →
Star Water Group
Filter media in the structural soil cells; conditions the substrate for root mass, oxygen and mineral transfer.
starwater.com.au →
Industry partner of the ARC Training Centre for Climate-Resilient Water – a national research centre led by The University of Queensland. The TNS™ itself has not been assessed by the ARC Training Centre.
Star Water filter media is a supplier product; performance data published on their site relates to their product in their applications. The TNS™ is offered on retention and storage, with load reductions that follow from retained volume shown as modelled in MUSIC. The TNS™ is not offered as a certified stormwater quality device.
Integrating modular tank, structural cell and drainage void systems – configured to depth, capacity and site type.
A street tree over a structural soil cell and tank module – fed by the EnviroKerb® and ETI.
View details →
A grassed verge served by the EnviroKerb®, water ramp unit, tank module and drainage cell.
View details →
EnviroKerb® feeding a drainage cell and tank module for stormwater retention beneath the pavement.
View details →
Planted surface over Rigofill ST modular blocks and RigoFlor™ geotextile – amenity above, storage below.
View details →
Water is a living system – intrinsically connected with land, culture and community. Our approach follows the long-held principle that water should return to Country and sustain life.
Consistent with Australia's National Water Initiative (2004), the Insights Paper – Pathway to Enduring Recognition of Aboriginal Peoples' Water Interests (2022), and the forthcoming National Water Agreement.
Whether you're specifying WSUD for a council or development, or a capital partner backing climate-resilient infrastructure – start a technical conversation.
We work with capital and delivery partners as well as councils and developers. Choose that in the form and it comes straight to Owen.
Owen, the inventor of the TNS™, has three decades in civil and water engineering, designing for flood, urban heat and street-tree health.
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