Part 9 – Landscaping Engineered Stormwater Devices
9.5 Mulching
The types of mulching specified are to ensure rapid planting establishment while maintaining good ground infiltration without souring the soil or causing negative amenity values, and allowing some scope for landscape design variations. Mulching for the PSDs shall be as detailed in Table 9.1.
Council favours biodegradable weedmats over synthetic geotextile weedmatting. No synthetic geotextile weedmatting is to be utilised in the installation of the landscaping portion of landscaping engineered stormwater devices. However, synthetic geotextiles and other materials may be used, as applicable, to meet device engineering requirements; for example, at inlets, outlets and high velocity channels.
Biodegradable matting must:
- Have a lifespan of at least 12 months.
- Prevent weed growth within the mulched area.
- Help stabilize the soil while plants are establishing.
- Not easily lift from the ground if submerged for periods of time.
- Appear reasonably tidy from a visual amenity perspective.
Examples of approved biodegradable matting products include:
- Coir matting, 10 mm thick minimum.
- Jute-Hessian weed control mats, 800 g/m² minimum.
- Densely woven flax matting.
Where shredded tree mulch is used, it is to be contained within the plant area that it is providing cover for. Shredded tree mulch is not permitted in any PSD:
- Within 3.0 m of any watercourse or water body.
- Where water ponding or flooding may occur.
- On slope gradients of greater than a 1:3 ratio.
Table 9.1 – Council Approved Landscape Mulching for PSDs
| Engineering device | Planting Zone | Mulch Type |
| Raingarden | All | Council approved biodegradable weed matting. 50–150 mm diameter River Rocks in 100–300 mm deep Council approved gabion matting. |
| Stormwater Pond | Amenity Planting – Site Entrance and Drainage Reserve Boundary Line to Upper Bank Zone where no ponding, flooding, or mulch travel is possible Amenity Planting – Site Entrance and Drainage Reserve Boundary Line to Upper Bank Zone where ponding or flooding is possible Upper Bank and Lower Bank Zones Marginal Zone Wet Zone |
Council approved Bark and/or aged Woodchip
Council approved biodegradable weed matting Council approved 0.5 m |
| Swale – River Rocks | All | Loose River Rocks on Council approved biodegradable weed matting 50–150 mm diameter River Rocks in 100–300 mm deep Council approved gabion matting |
| Swale – Roll on Turfing | All | No mulch |
| Swale – Vegetated (Carex Grasses) | All | Council approved biodegradable weed matting |
| Vegetated Filters | All | Council approved biodegradable weed matting |
Figure 9.1 – Stormwater Pond Staged Landscape Planting (click to enlarge)
Table 9.2 – Approved PSD Plant Species (click to enlarge)
