Strataflow

Water Harvesting with Strataflow

strataflowIn urban environments, we see a number of problems relating to stormwater and urban trees:

  • Stormwater runoff from roads and paved surfaces carries sediments, nutrients, and heavy metals – resulting in pollution of local creeks, lakes, and bays.
  • Rainwater falling on paved areas cannot soak into the ground, leading to increased stormwater which can cause flooding.
  • Typically, trees only receive rainwater which falls directly onto their leaves and the surface of the tree pit, meaning there is very little infiltration of water into the soil, resulting in declining tree health or the need for ongoing irrigation during hot weather and drought periods.

In response to these problems, we took our leading structural soil cell solution – Stratavault® – and modified it to create an innovative water harvesting solution. Strataflow® allows stormwater from surrounding paved areas to flow into structural soil cells – leveraging stormwater to enhance tree health and delivering a number of stormwater benefits in the process.

Benefits of Strataflow – a dual-purpose solution

With Strataflow, advanced structural soil cells are used to create an expanded soil area and capture stormwater runoff from surrounding surfaces. Benefits include:

  • Tree health benefits

    • Extended tree lifetime
    • Improved canopy cover
    • Increased shade and cooling
    • Better amenity value
    • Enhanced biodiversity value
    • Reduced pavement uplift and root intrusion
    • Reduced need for irrigation and tree care
  • Stormwater management benefits

    • Increased interception of stormwater by canopy and tree pit
    • Reduction of pollutants entering waterways and bays
    • Reduction and slowing of stormwater entering to underground drains to reduce flood risk
    • Local use of stormwater as an alternative water source for irrigation
    • Achieves best practice pollutant reduction targets

Design

Strataflow tree pit systems can be configured in a number of ways depending on your specific site opportunities and constraints. The fundamental elements of a WSUD tree pit system include the following;

  • Sufficient structural soil volume to facilitate tree growth and root expansion
  • Available impervious catchment for passive watering
  • Inlet for stormwater supply to tree
  • Suitable tree species
  • Treatment element for management of solids and pollutants in stormwater
  • Drainage layer and stormwater outlet connection (as required)

A design procedure has been prepared to assist specifiers and designers with the integration of WSUD features into Strataflow tree pit systems. The procedure is presented as a flowchart which describes the general steps involved in the design process. Download it here.

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The business case for using Strataflow

How does the Strataflow approach compare to traditional street tree and stormwater management approaches? Analysis of two typical urban developments in Australia, a carpark in Brisbane and a town centre in Canberra, show that Strataflow can achieve best practice stormwater treatment requirements while also significantly increasing tree canopy cover. What’s more, because of their dual function, Strataflow provide significant cost-benefits for both the developer and the ongoing asset managers.