Urbanisation has modified the natural environment and resulted in habitat fragmentation. There has been a loss of biodiversity, ecological processes have been highly modified. Decreased infiltration of water from rains due to diversion of rainwater to underground drainage. Increased pollutants and sediment from increased surface runoff is ending up into waterways and impacting its health. Extreme changes in the flows, including erosive and peak flows, are altering biodiversity in rivers. Increasing temperatures, causing urban heat island effect, in urban environments.
While such infrastructure may have been a good idea in the past. People are now realising the negative impacts. Daylighting streams is one of the recent trends to restore streams and waterways. Implementing green infrastructure is another strategy.
What is green infrastructure?
Green Infrastructure describes the network of green spaces and water systems that deliver multiple environmental, economic and social values and benefits. Plantings which provide ecosystem services in cities and replace ‘grey’ engineered infrastructure. Examples include rain gardens (biofilters), constructed wetlands, green roofs, gardens, street trees, green walls and facades.
Benefits of green infrastructure
- Mental health and well-being
- Physical health and exercise
- Cultural heritage (sense of place)
- Worker and retail productivity
- Increased property values
- Biodiversity (flora and fauna) ——Ecosystem Services
- Carbon sequestration —————Ecosystem Services
- Shade and cooling benefits ———Ecosystem Services
- Reduces particulate pollution——Ecosystem Services
- Reduced stormwater run-off ——-Ecosystem Services
- Climate regulation ——————Ecosystem Services
- Water purification——————-Ecosystem Services
- Regulate pests and diseases ——–Ecosystem Services
- Soil biodiversity ———————Ecosystem Services
- Cultural services ———————Ecosystem Services
Ecosystem services are the direct and indirect contributions of ecosystems to human well-being. They support directly or indirectly our survival and quality of life. Ecosystem services can be categorised in four main types:
- Provisioning services are the products obtained from ecosystems such as food, fresh water, wood, fiber, genetic resources and medicines.
- Regulating services are defined as the benefits obtained from the regulation of ecosystem processes such as climate regulation, natural hazard regulation, water purification and waste management, pollination or pest control.
- Habitat services highlight the importance of ecosystems to provide habitat for migratory species and to maintain the viability of gene-pools.
- Cultural services include non-material benefits that people obtain from ecosystems such as spiritual enrichment, intellectual development, recreation and aesthetic values.
Biofilters and Rain gardens
Raingardens are self-watering, low maintenance gardens designed to protect our rivers and creeks, by capturing stormwater that runs off hard surfaces after it rains. A raingarden is a water saving garden that is similar to a regular garden bed, but is designed specifically to capture stormwater from hard surfaces such as driveways, patios and roofs via downpipes after it rains.
Raingardens are an easy way to create a water-efficient garden and improve the health of your local creek.
Plants must be good when dry for most of the time and then exposed to inundation. Similar to ephemeral wetlands or riparian areas. Best plants to use include
- Deep fibrous roots best for pollutant removal, e.g. ficinia nodosa
- Leperonia articulata
- Lomandra hystrix
- Pennisetum alopecuroides
Design components of your rain garden
- If it doesn’t rain, water your garden until your plants have established
- Mulch your raingarden to keep your garden spongelike
- Weed regularly
- Break strong water flow to limit erosion from heavy rainfall
- Inspect your garden regularly – replace plants and repair erosion in your garden when necessary
- Don’t park, drive over or squash your raingarden. If your raingarden is squashed, it will loose its ability to soak water into the soil
Why build a rain garden?
How to build a rain garden?
- Energy Efficiency
- Reduce heat island effect
- Biodiversity and habitat
- Reduce quantity and improve quality of stormwater
Restoring cities at the landscape scale
Individual green infrastructure components can contribute to restoring the whole landscape. Green infrastructure is a useful too for improving ecological function and livability of cities. Each aspect has its’ own benefits/constraints. Natural ecosystems can be used as models to improve function. Integrating different technologies likely to increase benefits. Research is critical to overcome barriers for green infrastructure adoption and to make it more widespread. Ongoing maintenance in public urban environments are also a consideration given the cost and potential safety risks.