Water Sensitive Strategy

JOHNSTONS CREEK CATCHMENT WATER SENSTIVE DESIGN STRATEGY

DESC 9202: Water Sensitive Design ASSIGNMENT 2 Submitted by Husna Begum M R (500241114)

TABLE OF CONTENTS 01

INTRODUCTION

11

STREETSCAPE SCALE INTERVENTIONS

02

JOHNSTON CREEK CATCHMENT

12

EVALUATING WSUD STRATEGIES

03

REDEVELOPMENT SITE

13

WSUD ‘Unlimted’ DESIGN OUTCOMES

04

OBJECTIVES

14

CONCLUSION

05

OPTION: ALTERNATE WATER SUPPLY SOURCE

06

OPTION: ALTERNATE WATER SUPPLY SOURCE

07

OPTION: STORMWATER TREATMENT

08

WATERWAYS RESTORATION

09

LOT SCALE INTERVENTIONS

10

STREETSCAPE SCALE INTERVENTIONS

2 | JOHNSTON CREEK CATCHMENT

REFERENCES

DESC9202 Water Sensitive Design | Assignmnet 2

01

INTRODUCTION The report proposes development strategies for a site within the Johnston Creek catchment. The proposed strategic options - ‘WSUD basic’, ‘WSUD stretch’, ‘WSUD unlimited’ incorporates, various levels of Water Sensitive Urban Design (WSUD) principles and acts as an extension of the Johnston Creek Parklands Masterplan to transform the catchment in accordance to water sensitive framework.

Following are the summary of key moves considered in the Johnston Creek Masterplan, to transform the creek with the Water Sensitive framework

Fig Tree Planting Enhance mangroves and introduce intertidal saltmarsh Naturalised creek edge

• • • •

Use natural elements - water, plants as elemets for visual aesthetics Provide opportunities to interact with creek, natural environment Provide amenities for active and passive recreation Heal the country through naturalisation of creek Community Engagement

• • • • •

Make catchment as source of water supply to reduce reliance on potable water Introduce infrastructure to combat reverine and overland flooding Introduce flood resilient active recreation areas Naturalise creek with vegetation that is resilent for drought and flood events Improve water quality by reducing pollutants for resilient aquatic habitat

Treat water entering parklands with pollutants trap

Underground water tank Enhance Existing Salt Masrh

Re vegetation

Treat water entering parklands with pollutants trap Natural entry of water

Resilience

Water fountain

New Playground

Livability •

New Seating

Naturalised creek Naturalised Parkland

Ecological Integrity • • • •

Re vegetate the creek, parklands with native plants to link the flora and fauna habitat and increase biodiversity Naturalise the creek and revive the natural habitat in the ripirian corridor Use water as means to connect the natural habitat Improve aquatic life by improving water quality

Treat water entering parklands with pollutants trap

Map 1: Johnston Creek Parklands Master Plan (Author 2021) Base: (GoogleMaps 2021) Data: (City of Sydney, 2021) SCALE 1:10000

3 | JOHNSTON CREEK CATCHMENT

DESC9202 Water Sensitive Design | Assignmnet 2

02

JOHNSTON CREEK CATCHMENT Johnston Creek being the main stormwater canal in the catchment, drains storm water from its 460-ha catchment into the Rozelle bay. The catchment is divided by two jurisdictions, with 108 ha within the City of Sydney LGA and rest under the inner west LGA as show on Map 2. Although, the discussed Johnston Creek Parklands Master Plan, has incorporated WSUD elements, the masterplan is only a fraction of the entire catchment and the characteristics of the rest of the catchment would inevitably affect the creek and become potential threat to the WSUD intend of the masterplan (City of Sydney 2015)

ROZELLE BAY

LEGEND General Residential

Infrastructure

Low Density Residential

Neighbourhood Centre

Public Recreation

Mixed Use

GLEBE

LEICHHARDT

Permeability

City

The Johnston creek catchment was rapidly urbanised in late 19th century and early 20th century, transforming the largely pervious land use to impervious surface. Figure 1 along with Map 2 demonstrates the current land use of the catchment being dominated for the residential purpose, with the Table 1 exhibiting the low permeability of the residential land use.

The change in land use, has affected the creek, with increasing stormwater flow volume resulting in high peak flows (City of Sydney 2015).

dney of Sy st r We Inne

Drainage System

SCALE 1:20000

Figure 1: Landuse composition of the Johnston Creek Catch- Map 2: Landuse composition of the Johnston Creek Catchment (Author 2021) Base: (SixMaps The catchment is served by network of drainage sys2021) Data: (City of Sydney 2012; Inner West 2014) tem by council and Sydney water. The stormwater from ment (Author 2021) the property runs through the gutters through counLand Use Type % Pervious % Impervious cil’s drainage network until it reaches Sydney water’s major drainage trunk - SWC55 and SWC95, both of Residential 30 70 which empty into the Rozelle bay through the Johnston Public Recreation 100 0 Creek. The Johnston creek runs as an open channel Infrastructure 10 90 from the Salisbury road until the Rozelle bay, while the rest of the creek is covered channel as shown in Map 3.

Neighbourhood 30 70 The capacity of the drainage system varies at different Centre location in the catchment, leading to localised overland Mixed Use 0 100 LEGEND flooding for even minor rainfall events (City of Sydney Table 1: Permeability of different land use type in the catch2015; Inner West 2017) Pits ment (Author 2021) Data: (City of Sydney 2015)

Runoff Contaminants

The modified catchment with low permeability and piped drainage system, provides little opportunity to filter the pollutants and risks the waterways with the contaminants found in the catchment, such as: • Toxic Chemicals including cleaning prod• Rubbish / litter left by humans ucts, metals • Organic litter like leaves • Nutrients from pesticides, fertilizers of • Fine sediments from construction sites backyards • Microbes/Pathogens from sewage overflow, dog droppings • Oil, grease from vehicle (Annandale on the Web 2013; NSW epa 2020) • Leachate from contaminated Industrial and acid sulphate land 4 | JOHNSTON CREEK CATCHMENT

0.1-0.45 0.45-0.75 0.75-1.0 1.0-2.4 2.4-3.8 Open Channel

Map 3: Drainage System of Johnston Creek Catchment City of Sydney (City of Sydney 2015)

SCALE 1:20000

DESC9202 Water Sensitive Design | Assignmnet 2

REDEVELOPMENT SITE tree t son S son L

ane

Cre ek

Nel

nt resce

KEY PLAN

Nel

The redevelopment site is located at the lower catchment of Johnston Creek, with an interface of the creek as shown on Map 4. Although, the site with its gradual slope promotes natural drainage towards the creek, the area is subjected to localised flooding in the event of rainfall (Map 4). It is to be noted that the site has Class 3 contamination of Acid Sulphate soils (City of Sydney 2012 ). The site is surrounded with prominent historical and natural features like the Aqueduct and natural reserve, which is conserved and expanded in the proposed layout. With the location of the site adjacent to the Johnstons Creek Parklands Master Plan, provides opportunity to extend the vision of the Master Plan and transform it into a WSUD site.

C The

Site Characteristics

Smith, Hogan and Spindlers Park

Joh nsto ns

03

Four nos. ‘Narrow infill apartment’ lots

Nel

son

St

Extended Public Park

Public Park Private Open Space No. of Row Apartment blocks

963 sq. m 5,962 sq. m 6

No. of Infill Apartment blocks

4

Row Apartment building dimension

27 m (W) x 18 m (D)

No. of dwellings in each Row Apartment

12 apartments (2 BHK)

Infill Apartment Building dimension

13 m (W) x 37 m (D)

No. of dwellings in Infill Apartment

11 apartments (1 BHK-8 nos.; 2BHK- 3 nos.)

Table 2: Design Layout Details (Author 2021)

ree k ns C nsto

d ue Roa Minog

Joh

gue R oad

Extended canal reserve to naturalised creek

McMahon Reserve

Redevelopment Site Redevelopment Streetscape

Smith, Hogan and Spindlers Park

Smith, Hogan and Spindlers Park

Redevelopment Site m

ra ing

ad Ro

W

SCALE 1:7000 Map 4: Existing site conditions (Author 2021) Base: (SixMaps 2021) Data: (City of Sydney 2015; NSW 2020) Flood Depth (10% AEP) >1m

5 | JOHNSTON CREEK CATCHMENT

Two nos. ‘Row Apartments’ lots

Mino

11,765 sq m

cent

Total Redeveloped Area

Heritage Aquaduct Conserved

Cres

The site has been completely redeveloped, to extend the foreshore park and increase the number of dwellings. The site is redeveloped as per the NSW Housing Design Guidelines and incorporates 116 apartments within two apartment typologies as detailed in Table 2 (NSW 2020). The layout of the buildings and open space in the redeveloped site is demonstrated in the Map 5.

The

Proposed Design Layout

0.1-0.25m

d

Four nos. ‘Row Apartments’ lots

ram

a Ro

ng Wi

SCALE 1:5000 Map 5: Proposed site Layout (Author 2021) Base: (SixMaps 2021)

DESC9202 Water Sensitive Design | Assignmnet 2

04

OBJECTIVES An integrated set of objectives across various scale is recognised from the analysis of the catchment and subject site. The strategies are proposed at various scale to form a coherent treatment train and address the WSUD in the catchment and improve the health of the creek.

Primary Objectives • • • • •

Reduce potable water consumption Effectively re-use water from stormwater run-off and Gray water recycling Introduce site specific measures to address localised flooding Improve run off water quality and decrease flow volume Complement Johnston Creek masterplan

Streetscape Scale • • • • • •

Explore strategies to address localised flooding Explore alternate source of water supply for open spaces Reduce stormwater flow volume Reduce contaminates from stormwater run off Improve ecological value by restoring natural habitats Increase community awareness of WSUD

• • • •

Restore the ecological and cultural value of the creek Explore strategies to improve water quality and reduce floods Integrate Johnston Creek masterplan Increase community awareness of WSUD

Waterways

Weakness

SITE

Site Scale

• Localised overland flooding • Pollutants from catchment through storm water runoff • Modified geomorphology of creek / Engineered creek

• Minimise flooding, • Improve water quality • Restore ecological & cultural value • Improve community awareness of WSUD • Expand Johnston Creek Parklands Masterplan Opportunity

Strength • • • • •

Located on lower catchment Interface with the creek Adjacent to reserve/park Sloping topography Adjacent to Johnston Creek Masterplan

• Climate Change • Aging infrastructure • Governance & policy Threat

Secondary Objectives • • • • • • •

Improve water quality of the Johnston Creek & Rozelle Bay Improve aquatic life in the Johnston Creek & Rozelle Bay Reduce overland and riverine flooding events Improve the natural habitat of the Johnston Creek and catchment Reduce urban heat island effect in the catchment Contribute to healing the country by providing access to water Contribute to future goals of making the creek swimmable

6 | JOHNSTON CREEK CATCHMENT

DESC9202 Water Sensitive Design | Assignmnet 2

05

OPTION: ALTERNATE WATER SUPPLY SOURCE

Exemplar Case Study: Fishermans Bend Urban Redevelopment

The potable water supply in the catchment and the subject site, is majorly served through Sydney Water’s piped water supply network. A resilient redevelopment would find alternate local source of water supply, to reduce dependence on Sydney Water. The exemplar case study of Fisherman’s Bend suggests strategies possible strategies, which are tested for the subject site for the best possible business case.

Water Demand Calculation Unit Type

Total nos. of Units*

2 BHK

84

Water DeTotal Water mand per unit Demand per per day** (kL) day (kL) 447 37,548

1 BHK

32

238

7,616

Table 3: Water Demand Calculation of entire site (Author 2021)

* Table 2 data is used to find total number of units ** Water demand is the annual average water demand for small property as per Sydney water data; 2 BHK is assumed 3 occupancy and 1 occupancy in 1 BHK (Sydney Water 2021)

Total water demand per day = 45,164 kL/day

(CRC 2020)

The Fishermen Bend is located at the inner Melbourne and consists of integrated water management strategies at various level for 458 ha urban renewal project.

Considering the scale of the subject site, the case study is focussed to understand the interventions at the site scale. Like the subject site the Fishermen Bend has site constraints like localised flooding and contamination of ground.

Strategies The case study demonstrates strategies for Flood resilience & Alternate water supply. The Flood resilience is achieved through integrated solution of WSUD, building regulations, improvised levees working together. At the lot scale, smart rainwater storage tank and recycled water has been used for toilets, washing clothes, toilets, and irrigation to reduce dependency on mains water consumption as shown in Figure 3. However, it is to be noted that the recycling plant is at precinct scale serving 80,000 people, for a capacity 200% larger than the subject site, suggesting economics of scale.

DISH WASHERS BATH TUBS

Fixtures

%

Total Demand (kL/day)

Toilet Washing Clothes Outdoors

20 12

9,032 5,420

23

10,388

Showers

26

11,743

Bath Tubs

6

2,710

Dishwasher 1

452

Inside Taps

5,420

12

Table 4: Total Water Demand Breakdown (Author 2021)

INSIDE TAPS

TOILET

WASHING CLOTHES

SHOWERS

OUTDOORS

Non potable demand

Figure 3: Key moves taken for an integrated water management at Fishermans Bend Urban Redevelopment (CRC 2020)

Potable Demand / Graywater source Potable Demand

7 | JOHNSTON CREEK CATCHMENT

Figure 2: Water Demand Proportion (Author 2021) Data: (Sydney Water 2021)

DESC9202 Water Sensitive Design | Assignmnet 2

OPTION: ALTERNATE WATER SUPPLY SOURCE

RAINWATER TANK SIZE CURVING

As suggested by the Fisherman Bend Case study, the non potable water demand can be catered by alternate souce - Rainwater Harvesting and Grey Water Recycling.

RAIN WATER HARVESTING

Entire Site

Rainwater collected from rooftop is one of the cleanest sources of water supply. Although, few contaminants are possible like the pollutants from air and rooftop, various technologies like filters or first flush diversion exists to maintain the cleanliness of the rainwater (Grant 2016).

The rainwater is collected from the rooftop and stored in the storage tank for later use, however the subject site consistes of 10 lots and the harvesting process could be done either at individual lot scale or entire site scale. To analyse the best possible business case, the report tests the strategy at both the scales.

90% 80% 70%

60% 50%

40% 30%

20% 10%

0%

Roof Area per block (sq m)

Row Apartment Lot

486

Water Demand Non potable Water Appropriate per block per Demand per block Tank Size day (kL/day) per day (kL/day) 5,364 2,946 55 kL

% of non-potable demand met 48%

Infill Apartment Lot

481

3,245

1,785

60 kL

68%

Entire Site

4840

45,164

24,840

135 kL

40%

Table 5: Rainwater Harvesting capacity at various scales (Author 2021)

BUSINESS CASE The intervention at the lot scale caters to larger capacity,, however it requires more number of storage tanks.

Although the entire site approach may require limited number of storage tank, it can be argued the cost of laying pipes through out the site is more expensive. Hence, rainwater harvesting at lot scale is more feasible approach.

GREY WATER RECYCLING

Greywater is the wastewater discharged from showers, sinks, bathtubs. Although, the greywater is not as contaminated as sewage water, it has pollutants like soaps and organic matters like hair. Mostly, the greywater from kitchen sink is excluded, due to blockage and obnoxious smell from kitchen waste (Grant 2016). The grey water treatment consists of pre-treatment through filters to remove coarse pollutants, followed by purifying methods like constructed wetlands, activated sludge system and in larger systems methods like filtration, distillation, and reverse osmosis could be found. However, the treated water is finally sterilised through UV radiation (Grant 2016).v As suggested by the Fisherman Bend case study, economics of scale plays a significant role in greywater recycling system. Hence, it can be argued that precinct scale is a reasonable scale for grey water recycling. To avoid additional plumbing cost and avoid issues from kitchen waste, the report considers water from showers and bathtubs for recycling as outlined in Table 4. The available greywater from the entire site is 14,453 kL, which if recycled can supply to 58% of non-potable water demand.

8 | JOHNSTON CREEK CATCHMENT

65

70

75

80

85

90

95

100

105

110

115

120

125

130

135

140

145

150

Figure 4: Rainwater tank size curving (storage tank for entire site) (Author 2021)

Row Apartment Lot

Rainwater tank sizing curve

100%

Proportion of non-potable water demands met

Using Table 2, 3 & 4, the roof area, water demands are calculated

60

Rainwater tank size (kL)

90% 80% 70%

60% 50%

40% 30%

20% 10%

0%

15

20

25

30

35

40

45

50

55

60

65

Rainwater tank size (kL)

Figure 5: Rainwater tank size curving (storage tank for Row Apartment) (Author 2021)

Infill Apartment Lot

Rainwater tank sizing curve

100%

Proportion of non-potable water demands met

The rainwater storage tank size is calculated from the non-potable water demand, roof area, and 10 years historic rainfall data from the nearby observatory (Centennial park observatory). The appropriate tank size is determined at the point of inflection of the sizing curve as shown in Figure 4, Figure 5, Figure 6.

Scale

Rainwater tank sizing curve

100%

Proportion of non-potable water demands met

06

90% 80% 70%

60% 50%

40% 30%

20% 10%

0%

20

25

30

35

40

45

50

55

60

65

70

Rainwater tank size (kL)

Figure 6: Rainwater tank size curving (storage tank for Infill Apartment) (Author 2021)

DESC9202 Water Sensitive Design | Assignmnet 2

07

OPTION: STORMWATER TREATMENT The strategy aims to propose a treatment train that nearly imitates the ‘natural water cycle system’ and reduces the pitfalls of the existing pit and pipe drainage network as discussed in catchment analysis. The integrated water management plan aims to reduce the quantity of stormwater entering the drainage network and reduce the stormwater pollutants to improve the water quality in the creek and the support its related ecosystem.

EVALUATING OPTIONS The following stormwater treatment options are evaluated for their varying degree of impact on the flow volume, quality of runoff and possibility of application on the subject site.

SYSTEM

DETAILS

Gross Pollutants Trap (GTPs)

EVALUATION

Pre-treatment structures to traps pollutants larger than 5mm to prevent Can treat human / organic litter found in clogging down stream (Goonetilleke & Lampard 2019) the catchment, however has little effect on other pollutants and reduction of flow volume Green Roof Includes intensive (roof gardens) and extensive green roof which are Although the system is a viable option relatively light weight and low maintenance. The water absorbing sub- for stormwater retention, with limited strate reduces the peak flow volume through retention. A 100mm thick rainfall rainwater harvesting is preferrable substrate with 15%-30% void typically holds rainfall events less than option for the subject site as alternate 20mm (Grant 2016). source of water supply Permeable Reduces peak flow volume through infiltration, retention, and exfiltraReduces peak flow volume substantially, Pavers / Aus- tion of the stormwater. Achieved through porous pavement / reinforced but has little effect on treating pollutants trial Gravel grass top layer with coarse substrate like gravel, soils, and underground except for fine sediments Law drainage system to transfer the retained runoff to further treatment systems (Goonetilleke & Lampard 2019; Grant 2016).

APPLICATION: Load bearing pavements, lawn, carparking Biofiltration It improves stormwater quality through biological treatment and reduc- Has a high impact in reducing peak basins / Rain es peak flows through infiltration, retention, and exfiltration. It consists volume flow, and reduction of pollutants Gardens (Bio- of permeable vegetation layer which allows retention of water and acts like, coarse / fine contaminants, nutriretention) as carbon source for denitrification. The subsequent filter media (coarse ents, microbes, metals traffic pollutants. sand/fine gravel) allows infiltration to recharge ground water and perco- It acts as alternate source of water supply lation to perforated underdrain pipe. Depending upon the plants, it can to vegetation. treat pollutants like nutrients, traffic contaminates. A regular maintenance of the filter media is required with timely replacement to keep it permeable. It is to be placed at least 3m from the building’s foundation and covers 10%-30% of the area to be drained (Goonetilleke & Lampard 2019; Grant 2016).

APPLICATION: Verge, outdoor lawns, footpath Tree Pits Like raingarden, the tree pits are also considered as bioretention system Like Bioretention system, it has high imthat improve stormwater quality and reduces peak flow. However, it is pact on flow volume and pollutants, and an alternate to street planting by integrating it with stormwater drainacts as alternate source of water supply age system (Goonetilleke & Lampard 2019; Grant 2016). to street plants.

APPLICATION: Street Planting Vegetated Used as pre-treatment device to improve stormwater quality by infiltra- Conveyance system that reduces coarse Swales tion, adsorption, and biological uptake through vegetated top layer and / fine pollutants from stormwater and filter media. The longitudinal slope and cross section control the deten- has limited impact on controlling flow tion time and surface erosion (Goonetilleke & Lampard 2019) volume.

APPLICATION: Linear road verges

Exemplar Case Study: Elizabeth Street Catchment – Integrated Water Cycle Management Plan (IWCMP) (CRC 2018)

The Elizabeth Street is in the City of Melbourne and has been categorised as ‘extreme flood zone’. The case study is selected to understand the interventions applied to reduce the flood risks in the area and apply to the subject site which is prone to localised flooding as per the site analysis.

Strategies The Elizabeth Catchment (IWCM) Plan uses storage and permeable surface to mitigate the flood risks as shown in Figure 7. The plan takes a water cycle approach - reducing water consumption, stormwater, recycle water, through out the catchment. The water is stored in the upper segment of the catchment through permeable surfaces, to reduce peak flow volume and pollutants. The strategy acts as alternate source of water supply to for green spaces like parks, gardens, and trees. It provides secondary benefits like urban cooling, water / air purification and health & wellbeing of the community.

Figure 7: Integrated Water Cycle Management improving the liveability of the cities, reducing the peak flow volume and stormwater pollutants (CRC 2018)

Table 6: WSUD strategies for Stormwater treatment (Author 2021)

9 | JOHNSTON CREEK CATCHMENT

DESC9202 Water Sensitive Design | Assignmnet 2

WATERWAYS RESTORATION

Exemplar Case Study: Enhancing Our Dandenong Creek Program

As discussed in Assignment 1, Johnstons Creek and Rozelle Bay were rich source of fishing and food for the Wangal and Gadigal people. However, at present the creek is reduced to a storm water channel as shown in Figure 9. The strategy proposes extension of the Johnstons Creek Master Plan and naturalisation of the creek to restore its ecological, cultural, and historical value.

The strategy considers lessons from the exemplar case study of Dandenong Creek Program, and recommends site specific strategies like, naturalising of creek while considering appropriate depth to prevent flood, revegetation of the riparian corridor with native plants and engage community to explore the cultural values of the site.

Figure 9: Existing Johnston Stormwater Channel (Google Maps 2021)

Replace the existing fences with tall bushes to integrate the creek with the canal reserve

Naturalise the creek by replacing the concrete channel with natural surface. Ensure appropriate depth to prevent flood

The creek located in Melbourne was restored from an engineered covered stormwater pipe. The case study like the creek interfacing with the subject site was engineered into stormwater channel as shown in Map 5. However, the project aims to naturalise the creek and reduce the stormwater pollutants to restore the ecosystem

Strategies

Figure 10: Existing Shared Cycle/ pedestrian pathway (Google Maps 2021)

PROPOSED INTERVENTIONS Revegetate the ripirian corridor with native vegetation to restore the natural habitat

(CRC 2018)

EXISTING CONDITION

08

Retain the shared cycle/pedestrian pathway

1. Daylighting Creek: Stormwater pipe was replaced with open natural creek as shown in Figure 8 2. Restoring Habitat: The riparian corridor is re-vegetated to restore aquatic habitat and connection of Yarra people to the land 3. Community: Billabongs are created for public recreation and restore habitat 4. Water Quality: A detailed study is conducted to understand the source and pathways of the pollutants in the creek 5. Cultural Values: Signage installed through engagement with ‘Heathmont History Group and the Wurundjeri and Bunurong Traditional Owners’

Enagage with community to develop signages that reflect the cultural value of the creek

Private redeveloped site Smith, Hogan and Spindlers Park

Johnstons Creek

Figure 8: Naturalised section of the Dandenong Creek with restored ripirian corridor (CRC 2018)

Figure 11: Naturalised Johnston creek (Author 2021)

10 | JOHNSTON CREEK CATCHMENT

DESC9202 Water Sensitive Design | Assignmnet 2

09

LOT SCALE INTERVENTIONS

Austrian Gravel Lawn

The strategy proposes an integrated water management plan with interventions at the source (lot level), to emulate a near-natural water cycle system. The strategies explore WSUD methods to improve stormwater quality, reduce peak runoff, reduce reliance on network water supply, which improves the ecological value and liveability of the site.

Austrian Gravel Lawn

Gravel Compost Blend 0-32/45mm

30 cm

Gravel Subbase 0-45/64mm

20 cm

The outdoor green spaces are constructed as Austrian Gravel Lawn to increase stormwater infiltration and reduce runoff. The vegetation top layer of the lawn is treated with low-maintenance native plants, while the substrate consists of gravels as shown in Figure 13, which assists in stormwater retention and infiltration.

Rainwater Harvesting Stormwater is used as alternate source of water supply for non-potable usage like – ‘Toilets, Washing Clothes, Irrigation’. The rainwater from the roof top is collected and filtered for coarse pollutants through mesh filters and stored on a tank on rooftop. Calculation tabulated in Table 5, recommends a 55kL storage tank to cater 48% of non-potable water demand to all the 12 apartments in an individual row apartment building.

Greywater Recycling Greywater discharged from showers and bathtubs is transferred through separate plumbing for centralised recycling. A centralised recycling unit is recommended for economics of scale. The recycling process removes the pollutants through series of treatment process and sterilises through UV radiation. The system caters to 58% non-potable usage demand.

Subsoil

Water Efficient Fixtures & Appliances

Figure 13: Section of Austrian Gravel Lawn (Grant 2016)

Permeable Pavers

The apartments have 5-star WELS rating for all fitting, fixtures, in showerheads, toilets, kitchen, and bathroom taps with 5-star recommendation for dishwashers and washing machine appliances

Permeable pavers installed on the front setback reduces stormwater runoff peak flow volume and recharges ground water through infiltration. The voids in the underlaying substrate retains stormwater and discharges it slowly through an underground drainage pipe.

Rain Garden in the front lawn A one-metre-wide rain garden is provided at the front boundary of the site, to intercept and treat the stormwater runoff to the street.

The high-quality native vegetation layers treats the stormwater pollutants from the runoff and the underlaying filter media retains the stormwater, reducing the runoff peak flow volume.

11 | JOHNSTON CREEK CATCHMENT

MINOGUE CRESCENT Figure 12: WSUD interventions at the Row Apartment Lot (Author 2021)

SCALE 1:800

Monitor for consumption & Leaks A monitor for potable and recycle water usage is installed for the apartments; Plumbing is regularly investigated for leaks

DESC9202 Water Sensitive Design | Assignmnet 2

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STREETSCAPE SCALE INTERVENTIONS As discussed in the catchment analysis, the stormwater is drained through a pit and pipe drainage network, disturbing the natural ecosystem of the waterways through the pollutants and flow volume. Analysing the various WSUD strategies as in Table 6, a treatment train is proposed at streetscape scale as shown in Figure 14 and Figure 15. As localised flooding is a dominant issue of the site, stormwater retention, infiltration, storage have been given high priority along with pollutants treatment. Permeable surface, storage tanks have been introduced to increase the infiltration and retention of rainwater. Raingarden have been introduced at strategic location reduce peak flow volume and improve water quality.

Permeable Pavers Pedestrian pathway is made of permeable pavers material, to increase infiltration

Alternate Water Supply Filtered water is intercepted to provide alternate source of water supply for public amenities A

Redeveloped Apartments

McMohan Reserve

Strategic Placement of Rain Garden Considering the topography, rain garden is provided at only one street verge for maximum interception of stormwater

Redeveloped Apartments

Heritage Viaduct

EXPANSION Although, the proposed strategies are site specific, the rain gardens, tree pits, permeable pavers and storage tank can be replicated at other sites at well. The tree pits, permeable pavers can be replicated at almost all footpath in the catchment. As for the rain garden it should be placed at minimum of 3 meters away from the building foundation, and the street width should have sufficient allowance for one-meter -wide green strip/ rain garden. Interception of the rain garden can occur at locations near public amenities for alternate source of water supply.

Smart rainwater tank Active discharge of water into Johnstons Creek before the next rainfall event

Alternate Water Supply Sterilised rainwater used in public toilets and irrigating parks

Perforated Pipe Coveyance system that promotes infiltration

Terrain Slope A’ Existing Houses Figure 14: Mingoue Crescent Streetscape Plan (Author 2021)

Rain Garden Integrated with Tree Pits Considering the topography, is its provided at only one street verge for maximum interception of stormwater

SCALE 1:3000

Permeable Pavers Reduces runoff volume by promoting infiltration

SLOPE

PUMP

RAINWATER STORAGE

Tree Pits Tree pits integrated with rain garden to promote urba cooling along with biological treatment of stormwater

TO DRAINAGE NETWORK

Figure 15: Mingoue Crescent Streetscape Section AA’ (Author 2021) SCALE: NTS

12 | JOHNSTON CREEK CATCHMENT

DESC9202 Water Sensitive Design | Assignmnet 2

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STREETSCAPE SCALE INTERVENTIONS

The suggested bioretention rain gardens design is informed through the combination of ‘Manual for Rain garden design, construction, and maintenance manual’ from Christchurch council, and City of Sydney guidelines for rain gardens. The system consists of various layers as shown in Figure 16, for biological treatment, infiltration, and retention. A modified rain garden with tree pits, should ensure appropriate depth of biofilter media, and provide coarse gravel in the transition layer shown in Figure 16.

Gross/Silt Pollutant Trap

Mulch / Weedmat

Improves efficieny of raingarden by preventing clogging

50mm (75 max.) gravel mulch/ degradable weedmat at zero grade

BioFilter Media

Freeboard

600 mm (300 mm min.) deep filter media reduces pollutants like traffic contaminants, metals, nutrients, microbes depending upon the vegetations type.

Selection of vegetation for the rain garden is crucial for its performance. The vegetation should be resistant to prolonged wet and dry spell, with water filtering quality. Listed below in Table 7 is a sample Geotextile Membrane of indigenous plant species, suitable for rain garden with ability to prevent weed, invasive species growth. Prevent degeneration of nearby structural elements liek road, foundations For further list of diverse plant species, City of Sydney (2021) could be referred. A report by Great Rivers GreDrainage Layer enway (2021), suggest the plants to be planted tightly, 100mm thick layer consisting of fine gravel to prevent weed growth, soil erosion which may clog Raingarden Base the bioretention system.

Min. 300 mm thick loosen soil to promote Listed below, are also a sample of water efficient partial infiltration indigenous species which could be utilised in private and public lawn to restore the ecosystem. For further diverse list of plant species, Anandale on Web (2010) could be referred.

Freeboard provided to prevent overflow / flooding in peak rainfall events

Cleanout

300mm dia vertical standpipe provided to clean underlaying drainage system

Transition Layer

100mm thick layer consisting of coarse gravel

Perforated Drain

Figure 16: Treepit integrated rainwater garden detail (Author 2021) Data: (Christchurch City Council 2016; Grant 2016) SCALE: NTS

RAIN GARDEN

Provited at drainage network invert level to drain clean water into the pit and pipe drainage network

WATER EFFICIENT / XEROPHYTIC PLANTS Knotted club rush (Isolepis nodosa)

Thyme honey-myrtle (Melaleuca thymifolia)

Native Fuscia (Epacris)

Swamp banksia (Banksia robur)

Bottlebrush (Callistemon)

Wattle (Acacia)

Gymea lily (Doryanthes excels)

White correa (Correa alba)

Maiden Hair

Native Violet (Viola betonicifolia)

Mat Rushes (Lomandra)

Tree Spider Orchid (Dendrobium Tetragonum)

Table 7: Indigeneous Plant Species (Anandale on Web, 2010; City of Sydney 2021)

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EVALUATING WSUD STRATEGIES

WSUD Strategic options are proposed based on the varying degree of targets as detailed in table 8.

Each strategy is a cumulative of its preceding strategy, for instance the WSUD ‘Stretch’ is an addition to WSUD ‘Basic’. Although the higher-level strategic option, requires more intensive resources like investments, cross-organisation collaboration, and so on, they provide sophisticated ecological, communities services.

ECOLOGICAL INTEGRITY

RESILIENCE

LIVEABILITY

COMPARATIVE ANALYSIS While WSUD ‘Basic’ has no major intervention at urban scale, the ‘Stretch’ option contributes to mitigating flood and improving urban cooling through rain garden vegetation. However, the ‘Unlimited’ option enhanced urban cooling affect, along with supporting public amenities through water supply and restores the cultural value naturalising the creek and providing signage for storytelling.

While WSUD ‘Basic’ has limited effect on stormwater runoff it makes private development resilient from dry spell through rainwater harvesting, the ‘Stretch’ option through its strategic bio retention system mitigates flood events.

‘Unlimited’ option with its near-natural drainage system and catchment as source of water supply, makes the catchment resilient from flood and dry spell.

Although ‘Basic’ provides limited services in treating stormwater, the ‘Stretch’ option introduces major strategies to improve water quality. In addition, the integration of the bio retention system with drainage network and naturalisation of the creek with native species, restores the ecological value of the catchment to a greater extend in WSUD ‘Ultimate’.

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WSUD ‘Unlimited’

WSUD ‘Stretch’

WSUD ‘Basic’

The strategy is based on WSUD strategies as recommended in the exemplar WSUD case studies. It aims to achieve net zero mains water consumption. It aims to emulate near-natural system in urban management by developing resilient systems through restoring ecological integrity.

The strategy is based on WSUD strategies as recommended by City of Sydney development control plan. It aims to reduce mains water consumption more that 40%.

The target for stormwater pollutants is as mentioned below (City of Sydney 2012) • reduce the baseline annual pollutant load for litter and vegetation larger than 5mm by 90%.

• reduce the baseline annual pollutant load for total suspended solid by 85%; • reduce the baseline annual pollutant load for total phosphorous by 65%; and • reduce the baseline annual pollutant load for total nitrogen by 45%

The strategy is based on BASIX-Water target for residential development. It aims to reduce water consumption from mains by 40% and reduce the volume of stormwater runoff (BASIX 2021)

• Enhance rainwater harvesting system to supply for potable water consumption • Invest in centralised greywater recycling system to supply for non-potable water demand • Rain gardens and tree pits are integrated into urban drainage system with the filtered water being used as alternate source of water supply and not released into pit and pipe drainage network • Naturalise the waterways and revegetate the riparian corridor with native species • Engage with community as partners to understand and explain the cultural and ecological value of the Johnston Creek waterways

• Stormwater runoff is reduced by increasing the permeable surface in the private property – by using Permeable pavers, Austrian Gravel Lawn • Landscaping considers the runoff flow path to intercept the stormwater runoff • Stormwater harvesting system is installed in private development to cater for non-potable water demand • Gross pollutants trans and Stilt meshes are placed at strategic locations to intercept coarse and fine pollutants from clogging the pit and pipe drainage network.

• Rain Gardens are positioned at the location of localised flooding to reduce stormwater runoff and filter pollutants like nutrients, metals, chemicals, microbes from stormwater • The filtered stormwater from the rain garden is released into the pit and pipe drainage network

• Installation of WELS five start rating water efficient fixture and appliances • Installation of device to monitor water consumption • Regular maintenance to prevent leaks in fixtures and plumbing lines • Application of xerophytic / water efficient indigenous plants as listed in Table 7 for landscaping – private lawns, street verges • Application of permeable pavers in footpaths, cycleways

Table 8: Cumulative WSUD Strategic Option (Author 2021)

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WSUD ‘Unlimited’ DESIGN OUTCOMES CATCHMENT PROVIDING ECOSYSTEM SERVICES

WATER SUPPLY As discussed in Section 6: Alternate Water Supply Source; the non-potable water demand is 24,840 kL/ day (Table 5), which could be catered by recycled greywater and harvested rainwater as shown in Figure 17. However, the excess rainwater stored which after sterilisation through UV radiation could cater to 7% of potable water demand. The WSUD ‘unlimited’ entire process reduces 62% water consumption from mains, as illustrated in Figure 17.

Non potable demand

Harvested Rainwater 23%

Harvested Rainwater 7%

Recycled Grey Water 32%

Potable Demand

Figure 17: Water Supply Source (Author 2021)

CATCHMENT AS SOURCE OF WATER SUPPLY

STORMWATER TREATMENT As discussed in Section 2: Johnston Creek Catchment, the permeability of the catchment is evaluated as nearly 60% impervious (Table 9). As rain garden/ bio-retention system has been used as the major strategy to treat storm water pollutants in WSUD ‘Unlimited’, the Bioretention sizing curve has been used to estimate the minimum spread of the system for the target water quality, as shown in Figure 18. The suggested spread of 2% of catchment area is achieved through strategising the bio-retention system along the street verge of the Infrastructure landuse, apart from promoting it in residential, commercial, and recreational land.

Land Use Type

% of catchment 30

% Impervious

Public Recreation Infrastructure

100

0

10

90

Neighbourhood Centre Mixed Use

30

70

0

100

Residential

• Green habitat spread across riparian corridor, rain garden, roof garden, private and public land through native species vegetation would regulate the microclimate in the urban space and increase the local flora and fauna biodiversity • Emulation of near-natural water cycle system through stormwater retention and filtration would improve water quality and reduce the stormwater flow into the waterways preventing floods.

• The increased stormwater quality would restore the aquatic habitat of the Johnstons creek, restoring the cultural value of the creek (source of fish and food for the Gadigal and Wangal people) • Passive irrigation of the trees/plants through integrated tree pits would increase the urban canopy and promote urban cooling.

• Increase in permeable surface would improve soil moisture in the catchment

WATER SENSITIVE CONCIOUS COMMUNITIES • Provide opportunities through public amenities to engage with the naturalised creek • Develop signages through involving community to understand the cultural value of the land scape • Engage with industries, communities to implement water sensitive approach like reduction of pollu-tants, potable water usage at source

70

Table 9: Permeability of the catchment (Author 2021) Data: (City of Sydney 2012, 2015; Inner West 2014)

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• Integrated water management plan, with rainwater harvesting and Grey water recycling system would promote efficient use of potable water • Increase in permeable surface would improve groundwater level in the catchment • Passive irrigation is provided through integration of tree pits and vegetation with the urban drainage system • water supply for public amenities is catered through rainwater harvested from interception in the bio-retention system

Figure 18: Biorentention System Sizing Curve (City of Ryde 2015)

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CONCLUSION Johnston Creek historically provided ecological, cultural value to the community and was the rich source of food (fishing) for Gadigal and Wangal people (Wahlquist 2019). However, at present it is stormwater channel creating flood events in its catchment. Attempts to restore the degenerated system is observed in the Johnston Creek Parklands Master Plan through Water Sensitive Urban Design (WSUD) principles. However, the masterplan is only a fraction of the entire catchment area, and the remaining of the catchment is largely impervious and served through pit and pipe drainage network.

The engineering of the creek into stormwater channel and catchment with the drainage network, has increased the stormwater flow volume and introduced pollutants into the waterways, thus degenerating the natural habitat. The residential redevelopment at Mingoue Cres, provides opportunity to explore the WSUD benefits of the master plan and restore the ecological and cultural value of the creek.

The redevelopment of the residential lot supplies 116 apartments of 1BHK, 2BHK mix, in Row apartment and Infill apartment typology as pe NSW apartment guide (NSW 2020). The site is spread across 1.5 hectare and separated with McMahon reserve with an interface with the creek.

An integrated water management plan at different scales is essential to restore the ecological value. However, various strategies were individually tested before proposing an integrated treatment train at lot, streetscape, and waterways level.

Various ‘Alternate Water Supply’ and ‘Stormwater treatment’ strategies were explored. Rainwater harvesting at lot scale level proved economical, while grey water recycling at precinct level were observed feasible due to economics of scale. Various stormwater treatment options were tested for their efficiency in reducing peak flow volume and pollutants found in the catchment. The pollutants traps, permeable pavers / Austrian Gravel lawn provided some outcomes in stormwater retention & filtration. However, the bioretention systems (rain gardens), spread across the catchment covering at least 2% of the catchment area was observed to reduce the pollutants to the target level.

Considering the evaluation, treatment trains were proposed at lot, streetscape, and waterways scale. However, the interventions differed between WSUD ‘Basic’, WSUD ‘Stretch’ & WSUD ‘Unlimited’ strategic options. While the WSUD ‘Basic’, set its target as per BASIX standards, suggested ways to reduce consumption of mains water and stormwater runoff. The WSUD ‘Stretch’, in addition to ‘Basic’ strategies, provides ways to improve stormwater quality and mitigate floods through strategic placement of rain gardens. The retention of rainwater is improved drastically through Austrian gravel lawns, Permeable pavers, and strategic landscaping, thus mitigating the localised flood prevailing on the site.

In WSUD ‘Unlimited’, in addition to the preceding strategies, it provides high degree of liveability, resilience and ecological outcomes. The restoration of the creek with native plants and integration of the bio retention system with the urban drainage network, provides ecological service through urban cooling, restoration of natural habitat. In addition, passive irrigation through perforated drains, stormwater harvesting for public amenities makes the system resilient from flood and dry spells. The engagement of the community in the restoration of the waterways, with signage demonstrating the cultural and ecological value of the site improves the awareness of water sensitive sustainable approaches with the community. The strategy involves the communities as part of the WSUD solution.

Although, WSUD ‘Unlimited’ strategy provides higher degree of liveability, resilience and ecological services, intensive resources like investments, community motivation, cross-organisational collaboration is required for its successful implementation.

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CRC 2020, Collaborative planning for the Fishermans Bend Urban Redevelopment, Australia, viewed 31 October 2021 https://watersensitivecities.org.au/solutions/case-studies/ Goonetilleke, A & Lampard, J, L 2019, Stormwater Quality, Pollutant Sources, Processes, and Treatment Options, 1st edn, Elsevier, The Netherlands.

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Great Rivers Greenway 2021, Recommendations for Bioretention/ Rain Gardens, Missouri, viewed 31 October 2021, https://greatriversgreenway.org/design-guidelines/environmental/bioretention-rain-garden/ Inner West 2017, Johnstons Creek & Whites Creek Flood Study, viewed 31 October 2021, https://www.innerwest.nsw.gov.au/live/environment-and-sustainability/in-your-neighbourhood/rivers-and-waterways/flooding Inner West 2014, Leichhardt Local Environmental Plan 2013, viewed 31 October 2021, https://pp.planningportal.nsw.gov.au/publications/environmental-planning-instruments/ leichhardt-local-environmental-plan-2013 NSW EPA 2020, EPA fines Sydney Water $30,000 for sewage overflows, viewed 31 October 2021, https://www.epa.nsw.gov.au/news/media-releases/2020/epamedia201117-epa-fines-sydney-water-$30000-for-sewage-overflows NSW Government 2020, Low Rise Housing Diversity Design Guide, viewed 31 October 2021, https://www.planning.nsw.gov.au NSW Government 2020, Spatial Map Viewer, viewed 31 October 2021, https://portal.spatial.nsw.gov.au/portal/apps/webappviewer/index.html?id=44e72c6c7ccf498cb1c822b740c647d3 Sydney Water 2021, Water efficiency targets, Sydney, viewed 31 October 2021, https://www.sydneywater.com.au/your-home/saving-water-at-home/water-efficiency-targets.html Sydney Water 2021, Water use and conservation, Sydney, viewed 31 October 2021, https://www.sydneywater.com.au/education/drinking-water/water-use-conservation.html Wahlquist, Å 2019, The Foreshores of Glebe, Sydney, viewed 31 October 2021, http://asawahlquist.com/?p=341&fbclid=IwAR1yCp7NZqf39-w_BLtYOAsgl9se36R2f6TovuPBEJ5iDCupH0E8sGZ6A-w

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