Water management and streetscape enhancement
Stormwater Tree Pits – Impervious Streetscape, City of Moreland
Case Study Information
Study Details
Purpose of Project:
Streetscape enhancement
Installation Type:
Tree Planting Date:
June 2015
Tree Species:
Field Maple
Acer campestre
Number of Trees Planted:
25
Tree Stock Size at Planting:
20 – 45L container
Number of Trees Surviving:
22
Survival Assessment Date:
12 months
Features:
Other WSUD type
Owner of Site:
City of Moreland
Study Contact Details
Contact Name:
Vaughn Grey
Contact Phone
(03) 9240 2481
Contact Email:
Location Details
Location Address:
Barrow Street
25
Council/LGA:
City of Moreland
Technical Detail
If you require details not available here, see contact details.
Case Study Description
Further Details
Design &/or as constructed detail
Five replicates each of five different tree-pit treatment types – Control, Soil, Sand, Drained and Adjacent. The treatments are described in Figure 1 and Table 1 attached and as per “Establishing street trees in stormwater control measures can double tree growth when extended waterlogging is avoided”
The ‘Control’ treatment was a standard method for planting new street trees into native soil using a 1.2 m x 0.6 m opening cut into the asphalt footpath. While the Control treatment only received rainfall input from directly above, i.e. it received no runoff from the road, the other four treatments (Soil, Sand, Adjacent and Drained) captured runoff from a larger catchment (median catchment area 390 m2; range 180 m2 to 1900 m2) via a 1.2 m wide cut in the kerb. As per the Control, the ‘Soil’ treatment contained only native soil, however, the kerb was cut and an extended detention depth of 100 mm was excavated to capture runoff. The ‘Sand’ treatment was the same as the Soil treatment except, that the soil in the tree pit was removed to depth of 400mm and replaced with (from bottom to top): 75 mm of gravel (drainage layer), 25 mm of coarse sand (transition layer) and 300 mm of sandy loam (filter media, as per Payne et al. (2015)). The ‘Drained’ treatment was identical to the Sand treatment, except the gravel base layer contained a perforated PVC underdrain with a raised outlet connected to the stormwater drainage system. The ‘Adjacent’ treatment differed from the other three treatments receiving runoff, in that it combined aspects of the Sand and Control treatments. That is, runoff was directed into pit identical to the Sand treatment except that the tree was planted into native soil adjacent to the pit, rather than planted into the sandy profile.
Depth of Engineered Space:
Volume of Engineered Space:
See Figure 1 attached. Volume of biofiltration media in Sand, Drained and Adjacent treatments = 0.288 m3 (1.2 m x 0.6 m x 0.4 m)
Drainage Type:
Resource/Image/Document:
CONNECT
Surface Treatment:
Growing Media Detail:
Two media substrates:
- insitu soil (heavy clay)
- Biofilter sand
Surrounding Site Soil Detail:
Heavy clay, median exfiltration rate 6 mm hr-1
Surrounding Area Resource/Image/Document:
CONNECT
Watering Regime:
None
Maintenance Detail:
Bi-monthly inspection and removal of debris that may clog tree pit inlet or 10 cm deep extended detention zone
Non-Technical Detail
Challenges Overcome:
Installation quality control
Stakeholder Feedback:
Positive
Stakeholder Support for future projects of this kind:
Yes
Funding Source:
50% funded by Moreland City Council, 50% funded by Melbourne Water’s Living Rivers program
Partners/Sponsors Information:
Waterway Ecosystem Research Groups (WERG) and Green Infrastructure Research Group (GIRG) in the Faculty of Science, The University of Melbourne, Burnley campus. Stephen Livesley, Tim Fletcher, Chris Szota and Jasmine Thom
Background information can be obtained via this research paper.