Water Sensitive SA

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Practical ways to create water-wise microclimates in urban infill environments

June 20, 2016

Christie Walk. Source: Baden Myers

Words by Kate St James, FDIA

The future of our residential building landscape is moving ever-closer towards higher densities, especially in our cities. With the need to provide increased housing comes the need to consider the natural resources we will use to not only build these developments, but to also sustain them into the future.

All buildings have an impact on our environment. They are responsible for 40% of the world’s carbon footprint, 40% of the world’s energy use and 20% of the world’s drinking water. Future-proofing our environment is something that every developer must address, and one of the most critical assets to protect is our water. Water is the life-giving element of our planet. We need it not only for drinking and bathing but also for farming, manufacturing, and processing of goods and services.

Making our homes comfortable and energy efficient requires thoughtful, intelligent planning and design solutions. Using passive, low energy design is one way in which this can be achieved, including creating microclimates; those areas around buildings where the summer temperature may be lowered through the use of elements such as shrubs, trees, green walls, green roofs, ground cover, water features, irrigated garden beds, and rain gardens that collect and treat stormwater runoff from paved surfaces.

When creating built environments, it is important to understand individual landscapes and how they can work together. Creating lots of hard surfaces – such as paving, roads and rooftops – provide effective and efficient capture and transfer of water. Rather than all of this water being directed into stormwater drainage systems, it is more desirable to reintegrate some back into the urban landscape to improve soil moisture, which helps to sustain vegetation. The resulting evapo-transpiration from this vegetation in turn helps to cool our cities. Care should be taken within some sections of the Greater Adelaide area, as reactive clays restrict the opportunity for infiltration systems in proximity to footings of structures.

L-R Christie Walk, Old Treasury Lane - Source: Baden Myers; Adelaide Zoo’s green wall - Source: Water Sensitive SA

L-R Christie Walk, Old Treasury Lane – Source: Baden Myers; Adelaide Zoo’s green wall – Source: Water Sensitive SA

We can significantly improve the temperature both inside and outside of buildings, and hence save energy and money, through landscaping. Depending upon the geographical location and the desired outcome, landscaping can have a dramatic effect. Consider the impact of concrete paving and tarmac roads compared to soft landscaping such as plants used as ground cover, and hardy native grasses. The one can act as a heat sink, absorbing the heat of the day and re-radiating it a night, the other can create a more controlled constant temperature that can be humidified and kept cooler; important in high density environments.

Permeable paving allows rainwater to filter into the soil profile and replenish soil moisture. If paving an area with impervious materials is unavoidable due to the need for pedestrian or vehicular traffic, structural soil products can provide a reservoir for trees to store water and room for the establishment of healthy root systems.

Well-designed landscapes will also reduce the requirements for excessive water use. Using hardy natives that are drought tolerant is a sensible solution. Planting deciduous trees to the west and south-west while making sure not to overshadow neighbours, can help keep your home cooler in summer and warmer in winter. Very large trees may not be the most appropriate plants in higher density developments unless large public spaces exist, due to overshadowing. Therefore it is vital to take a holistic approach to ensure that appropriate landscaping is designed to suit each individual development.

Green walls and green roofs create microclimates and act as insulation too. They can stop heat from entering buildings in hot weather and can help to retain heat inside in colder weather. They also play a role in controlling air and noise pollution, provide habitats for flora and fauna, and can be a great way to grow edible plants for use in your kitchen and to share with neighbours, bringing a sense of community to residents.

Christie Walk, green roof. Source: Baden Myers

Christie Walk, green roof. Source: Baden Myers

Our weather conditions are complex and constantly changing. We use statistics gathered during many years of observation to assess their patterns. With our current knowledge it is fair to say that our summers will get hotter, therefore it is important to take an intelligent, mindful approach when designing and building houses to ensure that residents can enjoy a comfortable lifestyle that takes opportunities to re-integrate water into the environment creating cooling microclimate benefits.

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