9Structural Controls - Department of Water - The Western Australian ...

Figure 4. Newly constructed and
mulched swale. (Photograph:
Ardross Developments 2004.)
resources traditionally associated with maintenance of turfed median strips. Additionally, maintenance of
the native vegetation does not require the use of fertiliser, which consequently removes one of the sources
of nutrient inputs that is commonly associated with urban environments.
Plant species were chosen based on their growth form (low shrub and groundcover) and water requirements.
The indigenous plants have deep root systems that assist with maintaining the porosity of swale areas to
promote infiltration through the root zone.
Temporary barriers erected around the swales during the construction phase protected the swales from
sediment associated with greenfield development, such as from construction and wind erosion of disturbed
topsoil. The physical barrier also protected the swales from vehicle access, which can damage the swales
and compact the substrate, resulting in decreased infiltration rates.
Roads have been graded to direct flows in excess of the swale capacity to the designated storage node for
infiltration (Figure 2).
Results/achievements
The stormwater management system at Beachridge Estate has been in place since 2003 and has achieved
the design objectives for stormwater quantity management. All storm events to date, which have been small
to moderate, have been successfully infiltrated within the swales.
In planning this project, the Shire recognised an innovative approach was required for development so close
to the highly valued coastal environment. Although there were concerns about the function of a system
without pipes and potential impacts of stormwater infiltration, for example damage to infrastructure, the
benefits offered by the proposed stormwater system outweighed the perceived risks.
The approach to stormwater management implemented at Beachridge Estate demonstrates the ability of
non-traditional systems to perform flood protection, enhance aesthetics and more sustainably manage
surface and groundwater resources. Vegetation has established well and is protected by temporary low
barriers from wind erosion and vehicular access. The vegetation and mulch has successfully stabilised the
slopes of the swales.
The construction of narrower roads has provided an additional benefit of encouraging reduced traffic
speeds, and therefore improved safety and liveability of the development for pedestrians.
30 Stormwater Management Manual for Western Australia: Structural Controls
Figure 5. Swale with established native vegetation. (Photograph:
Ardross Developments 2007.)