Difference between revisions of "Stormwater Tree Trenches"

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*[http://www.conteches.com/Products/Stormwater-Management/Biofiltration-Bioretention/Filterra Contech - Filterra]
*[http://www.conteches.com/Products/Stormwater-Management/Biofiltration-Bioretention/Filterra Contech - Filterra]
*[https://greenblue.com/na/products/rootspace/ GreenBlue Urban - RootSpace]
*[https://greenblue.com/na/products/rootspace/ GreenBlue Urban - RootSpace]
*[http://http://www.storm-tree.com/index Storm-Tree]
*[https://www.storm-tree.com/stormwater-harvesting Storm-Tree]
*[https://citygreen.com/stratavault/ CityGreen Stratavault]
*[https://citygreen.com/stratavault/ CityGreen Stratavault]
[[Category:Green infrastructure]]
[[Category:Green infrastructure]]

Revision as of 17:39, 25 January 2022

Soil cellsSoil cellsBioretention: Filter mediaChoking layerReservoir gravelReservoir gravelReservoir gravelForebaysForebaysForebaysForebaysSlotted drainDepressed drainTreesTreesPerennials: ListPerennials: ListPerennials: ListOverflowOverflowUnderdrain
This is an image map of an extended tree pit, clicking on components will load the appropriate article.


Trees can be incorporated into bioretention cells with other plant types, or otherwise into their own planting pits.

Take a look at the downloadable Stormwater Tree Trenches Fact Sheet below for a .pdf overview of this LID Best Management Practice:


Planning considerations[edit]

A commonly held view is that a tree's root system will be similar to it's visible crown. For many trees, this is not the case, as roots will more often spread much more widely, but to a shallower depth [1]. For more detailed information on planning (site) considerations see Bioretention

Planting in slopes[edit]

Smooth slopes should be amended into localised terraces by the Landscape Architect when planting large trees into slopes > 5 %. [2]


There are many design configuration options for including trees into stormwater management plans.

Soil cells[edit]

These are (usually plastic) supporting structures placed around the trees and beneath adjacent paved areas. They prevent compaction to the roots of the tree and prevent root damage to the paving. They are sometimes configured to receive stormwater and to enclose ponded water which can then infiltrate the soil surrounding the tree. Things to consider in design:

  • If the system is unlined it is hydraulically equivalent to a bioretention cell and provides similar water quality benefits.
  • If the system is lined and underdrained it is hydraulically similar to a large stormwater planter. Depending on the design detail it may retain significant stormwater within the planting soil volume and will provide water quality benefits.


A surface inlet configuration featuring a depressed drain routing water collected from the street to an enclosed area infiltrating water to soil cells underneath.

Multiple methods for distribution and conveyance of runoff into the system are recommended for redundancy and conservative designs. Combinations may be made of:

  • tree well flow,
  • catchbasins and distribution pipes, and
  • direct infiltration from permeable paving.

See also Inlets and pretreatment

Species selection[edit]

For a detailed overview with in-depth information on species selection please visit our Plant lists wiki page and you can continue on to our further detailed tables showcasing how to develop planting plans that include selection of species for specific functions in several stormwater tree trenches and other LID practices.

Planting pit sizing[edit]

Bioretention: Sizing





Tree canopies intercept and store rainfall, thereby modifying stormwater runoff and reducing demands on urban stormwater infrastructure (Xiao et al., 1998; Xiao et al., 2000; Xiao and McPherson, 2002; Xiao et al., 2006). Canopy interception reduces both the actual runoff volumes, and delays the onset of peak flows (Davey Resource Group, 2008).

The extent of interception is influenced by a number of factors including tree architecture and it has been estimated that a typical medium-sized canopy tree can intercept as much as 9000 litres of rainfall year. (Crockford and Richardson, 2000).

A study of rainfall interception by street and park trees in Santa Monica, California found that interception rates varied by tree species and size, with broadleaf evergreen trees provided the most rainfall interception (Xiao and McPherson, 2002). Rainfall interception was found to range from 15.3% for a small jacaranda (Jacaranda mimosifolia) to 66.5% for a mature brush box (Tristania conferta now known as Lophostemon confertus). Over the city as a whole the trees intercepted 1.6% of annual precipitation and the researchers calculated that the annual value of avoided stormwater treatment and flood control costs associated with this reduced runoff was US$110,890 (US$3.60 per tree).


Trees suck! (Abstracted from Phyto, by K. Kennen)


Open tree pits[edit]

Soil cells[edit]

External links[edit]

In our effort to make this guide as functional as possible, we have decided to include proprietary systems and links to manufacturers websites.
Inclusion of such links does not constitute endorsement by the Sustainable Technologies Evaluation Program.
Lists are ordered alphabetically; link updates are welcomed using the form below.

  1. Crow, P. (2005). The Influence of Soils and Species on Tree Root Depth. Edinburgh. Retrieved from https://www.forestry.gov.uk/pdf/FCIN078.pdf/$FILE/FCIN078.pdf
  2. Wilkus A., 'Slope Style', Landscape Architecture Magazine, April 2018, accessed 21 December 2018, https://landscapearchitecturemagazine.org/2018/04/24/slope-style/