Urban water design
Urban development, including residential, rural-residential, commercial and industrial developments and associated infrastructure, can have significant impacts on water resources. Additionally, water resources can have significant impacts on the location, design, form and function of urban developments. The Department of Water being the lead water resources manager in Western Australia has a responsibility to protect, conserve and manage water resources. The broader view whereby the department works within the Western Australian Planning Commission governance is described under Water and land use planning.
As part of fulfilling this responsibility, the department assesses water management strategies and plans prepared under the Better Urban Water Management process. The department also provides water management and design advice on development proposals, including the state government's strategic and special projects, and advocates for and engages with various stakeholders so that the developments:
- address applicable water resource management components, opportunities and issues (e.g. water
service, stormwater/surface water and protection from flooding, groundwater, water quality, protection of receiving waters) with appropriate design and
implementation plans, as early as possible in the project planning stages - implement a water sensitive urban design approach
- design urban form and infrastructure and adopt appropriate construction practices that do not result in unacceptable impacts to water resources or unacceptable impacts from water resources on urban form and infrastructure
- recognise the need for site-specific solutions that include innovative approaches and appropriate non-structural and structural controls.
The department published the Water monitoring guidelines for better urban water management strategies and plans. These guidelines assist urban land developers to determine the pre- and post-development monitoring requirements of surface water and groundwater systems to support district water management strategies, local water management strategies or urban water management plans.
Some urban developments are located in areas with shallow groundwater. The process and considerations for a shallow groundwater management system are detailed in Water resource considerations when controlling groundwater levels in urban development.
Design of Public Open Space and water supply options for it is a significant issue with urban design. The Public Parkland Planning and Design Guide (WA) outlines how to achieve the best outcomes for planning and designing public parklands within the WA planning and water policy framework. The principles within the guide bring social, economic and environmental sustainability to the forefront of decision making.
Water sensitive design brochures
The department has published a series of brochures offering information on water sensitive urban design. Water sensitive urban design is an approach to the planning and design of urban environments that is 'sensitive' to the issues of water sustainability, resilience and environmental protection. The approach integrates the urban water cycle (including potable water, wastewater and stormwater) into built and natural landscapes to provide multiple benefits to society.
The brochures include information about the design and installation of water sensitive systems and will help those involved with water sensitive urban design in local governments, consultancies and developer companies, particularly managers and directors. Each stormwater device brochure provides a summary of the main benefits, design factors and target pollutants, as well as photos and/or diagrams.
Water sensitive urban design: an introduction
Provides an overview of urban water management objectives, treatment train approach and an introduction to the concept of design scale for the selection of suitable urban water management approaches. It also lists documents that support the application of water sensitive urban design.
Stormwater design considerations
Provides an overview of the factors that need to be considered when designing a stormwater management system for new urban developments or when modifying an existing system. It also provides the management objectives and performance outcomes for small, minor and major rainfall events.
Biofilters, also known as biofiltration systems, bioretention systems and rain gardens, are excavated basins or trenches that are filled with porous filter media and planted with specially selected vegetation to remove pollutants from stormwater runoff. These use natural and physical processes to treat stormwater. Biofilters have very flexible configurations and climate, soil and groundwater requirements.
Constructed wetlands for stormwater management
Constructed wetlands are extensively vegetated water bodies that use sedimentation, filtration and biological uptake processes to remove pollutants from stormwater. These wetlands are generally not suitable where contaminated or nutrient-rich groundwater is intercepted. Significant land areas are usually required for constructed wetlands because they need to accommodate large volumes of water.
Dry or ephemeral detention areas
Dry or ephemeral detention areas are depressions that temporarily hold stormwater and release it at a slower rate than it comes in. These reduce downstream flow rates and decrease flow velocities and help prevent downstream erosion. Dry or ephemeral detention areas improve stormwater quality by allowing sedimentation of particle-based contaminants. These are termed 'dry or ephemeral' as their lowest point is located above the maximum groundwater level and drain after each storm event to provide the full storage volume for the next storm.
Infiltration basins and trenches
Infiltration basins are depressions designed to capture and store stormwater before it reaches the soil profile. Infiltration trenches are below-ground linear devices that store stormwater prior to infiltration. Infiltration basins and trenches maintain site water balance and can replenish local groundwater.
Litter and sediment traps are devices that retain gross pollutants or litter and debris larger than 5 mm and coarse sediments with particles greater than 0.5 mm. These traps are available in several configurations and designs and many are commercial products.
Living streams are constructed or retrofitted stormwater conveyance channels that mimic the characteristics or morphology and vegetation of natural streams. As well as carrying stormwater, they also treat it using physical and biological processes and create diverse habitats for wildlife. Living streams can become complex ecosystems that support a wide range of plants and animals.
Pervious paving can be used as an alternative to traditional impervious hard surfaces used on roads, car parks, footpaths and public squares or plazas. Pervious pavement reduces runoff as some of the rainfall infiltrates into the soil below. Pervious pavement/paving can also provide an additional water storage system. There is a variety of pervious pavements such as porous asphalt, porous turf, porous concrete and permeable paving blocks.
Rainwater storage and reuse systems
Rainwater storage systems are a simple method of capturing rainwater, traditionally from roofs, for use as an alternative water supply source and to reduce consumption of scheme water. When installed and maintained in accordance with recommended guidelines, these can provide a high quality source of water.
Soakwells are a commonly used small-scale method of increasing infiltration into the ground as a way of managing stormwater. These generally consist of a vertical perforated cylinder and an open or perforated base, which provides maximum infiltration area.
Swales are grassed or vegetated broad, shallow channels used to collect and transport stormwater flows, promote infiltration, reduce stormwater peak flow rates and discharge volumes, and remove sediments. Swales use a combination of physical and biochemical processes to treat stormwater. Buffer strips are vegetated areas that reduce sediment loads from water flowing through them. Buffer strips are aligned perpendicular to water flow. Buffer strips are commonly used in conjunction with swales, living streams and constructed wetlands.