NOVEMBER 2020
WATER SENSITIVE DESIGN PROPOSAL DESC9202 Water Sensitive Design Assessment 2 The University of Sydney Unit Coordinator: Daniel Ryan Prepared by: Nayonika De
Introduction The main aim of this report is to comprehend the way the site has impacted the water cycle. The UN’s one of the sustainable development goals is to provide clean water. With increased urbanization and rapid climate change, the cities around the world and in Australia face
challenges in terms of water conservation and management (What is a water sensitive city?
- CRC for Water sensitive cities, n.d.). The climate plays a key role in water management. The weather of Sydney falls under the Cfa category which means, the region is dominated by
temperate, warm and hot summers and mild winters (Imteaz and Moniruzzaman, 2020).
Sydney’s rainfall pattern will continue to change with both wet and dry periods at the same
time. According to the Water Conservation Report (2018-2019), the dry condition will be consistent with dam levels at 52.1% as of 1st July 2019 in Sydney. Above 85% of Greater
Sydney’s water supply is dependent on rain which implies that there is a shortage of water
during drought (Environment Action Water management, n.d.). The below map of Australia shows the performance of cities when it comes to water sensitive urban design. Canberra,
Adelaide and Brisbane are performing much better in terms of water sensitive urban design implementation compared to that of Sydney (Elgendawy and Davies, 2019). Image source: Elgendawy and Davies, 2019
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Image source: Water sensitive cities, 2018 The data above shows the progress Greater Sydney is making utilizing the CRCWSC Framework. At present Greater Sydney is an 8% water sensitive city.
Image source: Urban water transitions framework (Brown, Keath and Wong, 2009; Hammer, Rogers, Chesterfield and Church, 2018) Sydney is following this framework to be a water sensitive city.
NSW’s planning for water sensitive urban design: State level NSW has formulated water sensitive urban design at the state level, but the implementation process is varied from the other five jurisdictions in Australia namely, Queensland, South Australia, Victoria and Western Australia (Choi and McIlrath, 2017). The State Environmental Planning Policy for NSW has mandated Building Sustainability Index: BASIX in 2004 for the developments to comply with water consumption targets and needs to reduce up to 40% potable water usage (Choi and McIlrath, 2017). This policy focuses on water efficiency (Choi and McIlrath, 2017). WSUD has not been clearly and broadly defined as a concept in the New South Wales planning system (Choi and McIlrath, 2017). Regional level According to the Greater Sydney Commission, a water sensitive city boosts sustainability, resilience and liveability of the cities which can be attained through strategic planning and design interventions by identifying how water can improve the environmental outcomes. The Greater Sydney Commission has identified the advantages of implementing a water sensitive design approach. A water sensitive Greater Sydney will include new and diverse water supply alternatives and provide resilience from the changing climate (Opportunities for a Water Sensitive Greater Sydney The importance of water in our city's future, 2016; Environment Action Water management, n.d.).
Image source: Water Sensitive Greater Sydney, 2016 Image depicting ideal water sensitive city City of Sydney and site The City of Sydney has prioritized the efficient utilization of water in the developments (City Plan 2036: Local strategic planning statement - City of Sydney, 2020; (04 Sustainability, 2020) including residential buildings. The Community Strategic Plan 2017-2021 by the City of Sydney has set the objective to enhance water sensitive urban design by including wetlands, bio-swales and rain gardens. Development Control Plan City of Sydney The local benchmark is the Development Control Plan which is a non-statutory document applicable for the site. The council encourages: Efficient utilization of roof water instead of mains supply for non-drinking purposes, particularly for toilet flushing and other domestic purposes; reutilization of surface runoff for non-portable purposes; utilization of greywater treatment methods to complement the existing water supply; infiltration of stormwater Existing challenges site and Sydney context With changing climate and rainfall patterns, management of water is under pressure (Environment Action Water management, n.d.) to meet the existing requirements. Droughts, floods and heat days are more frequent (Environment Action Water management, n.d.). The ongoing infrastructure development has caused reduced stormwater absorption and has also caused stormwater pollution (Environment Action Water management, n.d.).
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The city of Sydney has set the target to zero increase in portable water consumption by 2030 from 2006 and minimize stormwater pollution load by 50%. Climatic conditions The rising drought situations will also impact the existing built environment other than the green spaces (Adapting for Climate Change A long term strategy for the City of Sydney, 2017). The University of Sydney and the City of Sydney Council took the initiative to work on developing a climate change adaptation strategy for Sydney with a focus on the increased use of recycled water and focusing on water sensitive design. The microclimate of the site derived from Central Resource for Sharing and Enabling Environmental Data in NSW indicates the site is 3-6 degrees warmer than the baseline. This data of urban heat island is key to water sensitive urban design for the site of study. The objectives of the site includes: Reduction of water usage Improving stormwater runoff quality Reduction of runoff rate
Image source: Google Maps, 2020
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Site overview The site is a residential building in the suburb of Glebe. It is in close proximity to the Johnstons Creek Parkland, the site chosen for the previous assessment. The site is located in a highly urbanized landscape with an impervious surface. After analyzing the national context in terms of water sensitive framework and the regional and city context, the site has been chosen based on the challenges mentioned above. A SWOT analysis had been conducted to frame the design interventions suitable for the site. SWOT analysis
Water Sensitive Design interventions The design interventions have been divided into two categories: internal and external design solutions. External Design Strategy Infiltration rain garden
Source: Rain-Garden Design and Implementation for Kansas Property Owners, 2007 Features of an infiltration rain garden: Manages runoff capacity by gradually distributing water in the soil Eliminates pollutants by cleaning pollutants Rain gardens form a significant component of water sensitive urban design and are therefore advised to be integrated in urban design and planning policies (Lariyah and Elyza, 2012).
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6 The main aim of the rain garden is to minimize the negative effects of the stormwater pouring to the bigger water bodies (Schmidt, Shaw and Dods, 2007). In the past few years, rain gardens have been considered as one of the best water management practices to slow down and infiltrate as much stormwater as possible (Schmidt, Shaw and Dods, 2007). Rain gardens can be readily customized/ designed to catch and infiltration of stormwater on almost any residential property irrespective of soil type and slopes (Schmidt, Shaw and Dods, 2007). Someone has rightly said that- “something is better than nothing�. In the site context, the rain garden is appropriate and will function well as the water will flow regularly as it is in downslope (Schmidt, Shaw and Dods, 2007). Choosing of native plants in such a rain garden will help the site at the time of drought and other extreme climatic conditions (Schmidt, Shaw and Dods, 2007). The native plants require minimal maintenance and watering once planted (Schmidt, Shaw and Dods, 2007; Raingardens | Melbourne Water, n.d.). On top of that the root systems of the native plants help with cleaning stormwater quickly (Schmidt, Shaw and Dods, 2007). As a result it reduces cost, effort, resources and time to set up thus benefiting the site. In the site context, the installation of a rain garden will slow and infiltrate the stormwater before it drains to the Blackwattle Bay (Explainer: What is a rain garden? | City of Sydney - News, n.d.). Water-resistant plants like basket grass, tropic belle and native rosemary have special filtering properties (Explainer: What is a rain garden? | City of Sydney - News, n.d.). The use of recycled crushed grass and sandy soil will assist in cleaning rubbish from the flowing rainwater (Explainer: What is a rain garden? | City of Sydney - News, n.d.; Raingardens | Melbourne Water, n.d.) before it drains through the stormwater channel. National rain garden initiative, Melbourne The City of Melbourne has developed a Water Sensitive Urban Design guideline to actively promote water management. In order to maintain the city as a catchment, initiatives have been taken to develop rain gardens for the buildings in Melbourne (City of Melbourne WSUD Guidelines, 2014). Canterbury Neighborhood Centre is one of the similar examples of rain gardens in Melbourne (City of Melbourne WSUD Guidelines, 2014). International raingarden best practice, Portland Portland has encouraged residential buildings to set up rain gardens (How to manage stormwater rain gardens, n.d.) which can be proposed in the site as well as in Sydney.
Image source: Sanicola, Lucke and Devine, 2018 Using permeable pavements to reduce the environmental impacts of urbanisation (Sanicola, Lucke and Devine, 2018).
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Source: Australian paving, n.d. PICP
Permeable Interlocking Concrete Pavers (PICP) chosen for the site will encourage the
infiltration of stormwater, and at the same time, reduce stormwater runoff volumes and the
pace of flow (Sanicola, Lucke and Devine, 2018). Permeable pavements have proved to have benefitted the stormwater management and environment (Sanicola, Lucke and Devine,
2018). The site has 939.41 m2 (total site area- 1649.41 m2) - (building area-710 m2) that has impermeable surface. The calculated remaining 939.41 m2 area of the site has the potential
to improve from non-permeable to permeable surface, that reduces the surface stormwater runoff and is effective in removing pollution. PICP with permeable paver as the design
characteristics can reduce the runoff volume by 72.2% with a reduction of 33.6% TP and 66.9% TSS as discussed by Liu, Feng, Chen and Deo (2020). The major constraint of the site is that it has a car parking area because of which much vegetation cannot be designed. Rainwater harvesting tank
As mentioned earlier, Greater Sydney relies on 85% rainwater for its water uses and this
indicates that during drought, the region will be heavily impacted (Environment Action Water
management, n.d.). Rainwater tank is a useful way to catch and store rainwater from the roof to be utilized for non-potable water consumption purposes (Rainwater tanks, n.d.). It is
important to install first flush diverters are a significant part of the rainwater harvesting
system (Why Use First Flush Diverters?, n.d.) before storing it for further non potable usage. The chosen site can capture 738.4 L of water which is approximately the household water consumption per day for 2 units.
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Source: Bunnings, n.d. The image of the rainwater tank has a capacity of 1000L which would be suitable based on the existing rainwater holding capacity in the site.
Internal Design Strategies
9 Image source (left to right): Vacuum Toilets Australia, n.d., Delabie time flow tapware & showers, n.d., WELS Showers ¡ Smart Approved WaterMark, n.d. New water fixtures (left to right): Vacuum toilet with 0.5 L/flush Price: $ 1200 6 star Time flow tap with 3.5 L/7 seconds Price: $262 approx. 6 star Rain shower Price: $ 191.95 6 star
Image source: City of Sydney, 2014 Existing floor plan Current water usage calculation (Prices for your home, n.d.): Household size: 2.04 (Household size | City of Sydney | Community profile, n.d.) Total units: 16+16= 32 Bath- 300 L Toilet- 44 L Hand wash and other- 100 L Total household consumption each (includes water wastage)- ~444 L No. of residents: 2.04 (household size)* 32 (units)= 65.28 ~ 65 Current building water consumption each day: 32 (units)*444= 14,208 L or 14.2 Kiloliter Current building water consumption quarterly: 92*14,208 L= 1,307,136 L or 1307.1 Kiloliter Current annual water consumption: 14,208 L * 365 days= 5,185,929 L or 5,186 Kiloliter
10 Current water bill: $24.30 (quarterly service charge ) *32 + $2.11 (quarterly drinking water charge)*1307.1 Kiloliter (quarterly water consumption 32 units)= $3535.6 Current annual water bill amount - 3535.6*4 = $14142.4 Water bill for 12 years - $169708.8 New Calculations: Bath- 135 L Toilet- 2 L
Hand wash and other- 100 L
Total household consumption each (includes water wastage)- ~237 L
Projected building water consumption each day: 32 (units)*237 L= 7584 L or 7.6 Kiloliter Projected building water consumption quarterly: 92* 7,584 L= 697,728 L or 698 Kiloliter
Projected annual water consumption: 7,584 L * 365 days= 2,768,160 L or 2768.16 Kiloliter
Projected water bill: $24.30 (quarterly service charge ) *32 + $2.11 (quarterly drinking water charge)* 698 Kiloliter (quarterly water consumption 32 units)= $2250.38 Projected annual water bill amount - 2250.38*4 = $9001.52 Projected water bill for 12 years - $108018.24
Quarterly bill amount difference/ Cost savings: $3535.6 - $2250.30= $1285.3Proposed cost of new sanitary fixtures (32 units) - $51473.92 Installation costs (32 units) - $10294.78 Total cost of upgrade - $ 61768.70
Time period required to recoup - $61768.7/$1285.3= 48 bill cycles 48*3 months= 144 months (cost recovery in 12 years) Conclusion
The proposed design strategies will help achieve the objectives set for the site. The water
consumption for the site will be reduced in the next 12 years. However, 12 years is along term to see the reduced water usage outcomes in the chosen site of study. The rainwater tank is
small compared to the water demand for the site as the roof area is insufficient to catch the rainwater. It will not be enough for 32 units as the present consumption for 2 units is 888L
which is more than the volume of rainwater that can be captured in the site i.e. 738.4L. The
design proposals will work better for larger areas like the city of Sydney and Greater Sydney as the calculations indicated above show that it is not feasible for the chosen site given the scale of the site. The suburb where the site is located has 53.7% of the population as renters and social housing dwellers (Housing tenure | City of Sydney | Community profile, n.d.).The
housing tenure will also play a role in determining if the residents will be willing to accept the proposed changes based on their lifestyle, income and tenure.
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