Presentation to the NSW stormwater Industry Association conference 2017 Newcastle Raingardens are on the extreme edge of viability for growing plants. This makes them very vulnerable to even minor climatic variation. With Sydney's population set to grow by 1.7M by 2030, nearly 300 football fields worth of raingardens will need to be built just in Sydney's west alone. This is a half billion dollar investment. In the next decade we are likely to experience another El Niño event, that will put great strain on these systems. More consideration is needed in designing these systems to ensure they have more inbuilt resilience, to longer dryer events. This paper looks at contributing factors to plant failure’s in some of the raingardens at “The Ponds” after 9 years of growth. There were a multitude of factors, but drought stress was thought to be a key contributing factor. Drainage design, media mix, planting species layout and even the shape of the rain gardens also contributed. Raingardens by their very nature have high infiltration rates, poor moisture retention and nutrient stripping. Conditions diametrically opposed to plant growth. Some of the raingardens at The Ponds were designed as a dry gardens but were converted at time of construction to effectively a wet sump system by a simple weir in the outlet pit. When these were removed six years later there was a dramatic decline in plant survival. Counterintuitively the Music modelling was showing the wet sumps did not perform as well on a m2 basis. Given the intrinsic importance of planting to raingarden function and aesthetics, this paper looks at some considerations and thoughts in designing for survival. It looks at options to mitigate the extreme conditions we are creating in raingardens. The intent being to ensure we have greater resilience in the planting for better long term outcomes.

1. SIA 2017 NSW Cconference
LANDSCAPE ON THE EDGE
Building long term resilience in raingarden planting

2. LANDSCAPES ON THE EDGE
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 2

3. LANDSCAPES ON THE EDGE
Raingarden media
design at odds with
plant survival
• high infiltration rates
• low moisture retention
• nutrient stripping
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 3

4. 12 1312 13
Between 2006 and 2036 Sydney is set to
grow by 1.6M people
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 4

5. 12
The North west Growth sector: 10,000 Ha,
70,000 dwellings, 200,000 residents
The South west growth sector: 17,000 Ha,
110,000 dwellings, 300,000
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 5

6. Assuming 1% per Ha for raingardens
that is 270Ha of raingardens required for Sydneys west
or about 320 soccer fields worth
x 320
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 6

7. and over half a $ Billion @ $200/m2 to construct
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 7

8. In 2006 we began work on“The Ponds” now home
to 10,000 residents, and 26 raingardens
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 8

9. Here is one of our raingardens in 2012
five years after it was planted in 2007
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 9

10. They seemed bulletproof...
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 10

11. Here is the Jilluk pond raingarden in 2012
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 11

12. but by 2014 - it had suffered serious planting failure
....what had gone wrong?
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 12

13. Climate / rainfall
Maintenance regime
Infiltration
Media type
Soil moisture
Species selection
Planting design
Raingarden shape
So we started to look at what might have changed
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 13

14. CLIMATE / RAINFALL 2013
Significant 4 month dry event
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 14

15. MAINTAINANCE REGIME
Reports of raingarden plants being slashed
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 15

16. MAINTAINANCE REGIME
Inbuilt baffle plates removed at request of Council
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 16

17. MAINTAINANCE REGIME
These took 2 days to drain
Estimated Quarter of a million litres water buffer lost
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 17

18. Initial design rate
500 mm / hr
Long term Design rate
150 mm / hr
INFILTRATION RATES
431
639715
297
620
RG 2 RG 3 RG 8 RG 11 RG 12
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 18

19. MEDIA TYPE
TWO DIFFERENT MEDIA TYPES
Typical sand blend
Glass sand blend
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 19

20. SOIL MOISTURE
Plant size decreasing with soil moisture gradient
with distance from inlet spreader
Stormwater /
spreader outlet
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 20

21. PLANT SPECIES
CODE / BOTANICAL NAME COVERAGE %
Gah sei / Gahnia siebernia
Iso nod / Isolepsis nodosa
Jun usi / Juncus usitatus
Lom cas/ Lomandra ‘Classica’
0 20 40 60 80 100
SPECIES SELECTION
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 21

22. PLANT SPECIES
CODE / BOTANICAL NAME COVERAGE %
Gah sei / Gahnia siebernia
Iso nod / Isolepsis nodosa
Jun usi / Juncus usitatus
Lom cas/ Lomandra ‘Classica’
0 20 40 60 80 100
SPECIES SELECTION
Generally, but not uniform failures of wetter species
Top three on Blacktown City Council Raingarden list
Juncus usitanus
Isolepsis nodosa
Carix apressa
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 22

23. RAINGARDEN ID 1 2 3 4 5
PLANT SPECIES
CODE / BOTANICAL NAME COVERAGE %
Car app / Carex appressa
Cau pen / Caustis pentandra
Dia cae / Dianella caerula
Gah sei / Gahnia siebernia
Iso nod / Isolepsis nodosa
Jun usi / Juncus usitatus
Lom cas/ Lomandra ‘Classica’
Lom kat / Lomandra ‘Katrinus’
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100
RAINGARDEN ID 6 7 8 9 10
PLANT SPECIES
CODE / BOTANICAL NAME COVERAGE %
Car app / Carex appressa
Gah sei / Gahnia siebernia
Iso nod / Isolepsis nodosa
Jun usi / Juncus usitatus
Lom cas/ Lomandra ‘Classica’
Lom hys / Lomandra hystrix
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100
RAINGARDEN COVERAGE RATE SCHEDULE
S16-145 THE PONDS RAINGARDEN REVIEW05/05/2017 • ISSUE B
KEY:
INDICATES 0 - 30% COVERAGE
INDICATES 30 - 50% COVERAGE
INDICATES 50%+ COVERAGE
SAND SOIL BED MIX
GLASS SAND BED MIX
AVERAGE HYDRAULIC CONDUCTIVITY VALUE (KFS)200mm/hr
620mm/hr
715mm/hr3086mm/hr 297mm/hr
RAINGARDEN ID 11 12 13 14 15
PLANT SPECIES
CODE / BOTANICAL NAME COVERAGE %
Car app / Carex appressa
Cau pen / Caustis pentandra
Dia cae / Dianella caerula
Fic nod / Ficinia nodosa
Gah sei / Gahnia siebernia
Iso nod / Isolepsis nodosa
Jun usi / Juncus usitatus
Lom cas/ Lomandra ‘Classica’
Lom kat / Lomandra ‘Katrinus’
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100
RAINGARDEN ID 16 BASIN 17 18 19 20
Car app / Carex appressa
Gah sei / Gahnia siebernia
Iso nod / Isolepsis nodosa
Jun usi / Juncus usitatus
Lom cas/ Lomandra ‘Classica’
Lom kat / Lomandra ‘Katrinus’
Lom sha / Lomandra fluvialtilis
Lom hys / Lomandra hystrix
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100
RAINGARDEN ID BASIN 21 27 28
Car app / Carex appressa
Iso nod / Isolepsis nodosa
Jun usi / Juncus usitatus
Lom cas/ Lomandra ‘Classica’
Lom fil / Lomandra filiformis
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100
DRAFT
266mm/hr
639mm/hr451mm/hr
8
Iso nod / Isolepsis nodosa
Jun usi / Juncus usitatus
Lom cas/ Lomandra ‘Classica’
Lom kat / Lomandra ‘Katrinus’
0 20 40 60 80 100 0 2
RAINGARDEN ID 6 7
PLANT SPECIES
CODE / BOTANICAL NAME COVERAGE %
Car app / Carex appressa
Gah sei / Gahnia siebernia
Iso nod / Isolepsis nodosa
Jun usi / Juncus usitatus
Lom cas/ Lomandra ‘Classica’
Lom hys / Lomandra hystrix
0 20 40 60 80 100 0 2
05/05/2017 • ISSUE B
KEY:
INDICATES 0 - 30% COVERAGE
INDICATES 30 - 50% COVERAGE
INDICATES 50%+ COVERAGE
S
G
A200mm/hr
8
CODE / BOTANICAL NAME COVERAGE %
Car app / Carex appressa
Cau pen / Caustis pentandra
Dia cae / Dianella caerula
Gah sei / Gahnia siebernia
Iso nod / Isolepsis nodosa
Jun usi / Juncus usitatus
Lom cas/ Lomandra ‘Classica’
Lom kat / Lomandra ‘Katrinus’
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80
RAINGARDEN ID 6 7 8
PLANT SPECIES
CODE / BOTANICAL NAME COVERAGE %
Car app / Carex appressa
Gah sei / Gahnia siebernia
Iso nod / Isolepsis nodosa
Jun usi / Juncus usitatus
Lom cas/ Lomandra ‘Classica’
Lom hys / Lomandra hystrix
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80
05/05/2017 • ISSUE B
KEY:
INDICATES 0 - 30% COVERAGE
INDICATES 30 - 50% COVERAGE
INDICATES 50%+ COVERAGE
SAND SOIL BED MIX
GLASS SAND BED MIX
AVERAGE HYDRAULIC CONDUCTIVITY VALUE (KFS)200mm/hr
620mm/hr
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 23

24. PLANTING DESIGN AND RAINGARDEN SHAPE
Radiating planting impacted by moisture gradient
4
7
RAINGARDENS 7 AND 4
NEARMAP IMAGERY 02/09/2013
RAINGARDENS 7 AND 4
NEARMAP IMAGERY 26/06/2014
Juncus usitanus thriving in
both Raingardens 7 and 5.
Isolepsis nodosa not
establishing in Raingarden
7.
Isolepsis nodosa surviving
in Raingarden 5
4
7
Juncus usitanus failing in
both Raingardens 7 and 5.
Isolepsis nodosa relatively
unchanged in Raingarden
7.
Isolepsis nodosa showing
some level of losses in
Raingarden 5
Isolepsis nodosa thriving in non
raingarden edge landscape areas
09/
2013
06/
2014
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 24

25. NEXT STEPS / RECOMMENDATIONS
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 25

26. Real world data needed
NEXT STEPS / RECOMMENDATIONS
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 26

27. Real world data needed
MUSIC modelling update
NEXT STEPS / RECOMMENDATIONS
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 27

28. Real world data needed
MUSIC modelling update
Research on media types
NEXT STEPS / RECOMMENDATIONS
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 28

29. Real world data needed
MUSIC modelling update
Research on media types
Wet sump essential
NEXT STEPS / RECOMMENDATIONS
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 29

30. Real world data needed
MUSIC modelling update
Research on media types
Wet sump essential
Slow release nutrients
NEXT STEPS / RECOMMENDATIONS
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 30

31. Real world data needed
MUSIC modelling update
Research on media types
Wet sump essential
Slow release nutrients
Species diversity
NEXT STEPS / RECOMMENDATIONS
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 31

32. Real world data needed
MUSIC modelling update
Research on media types
Wet sump essential
Slow release nutrients
Species diversity
Planting design
More organic content to
media
NEXT STEPS / RECOMMENDATIONS
LANDSCAPES ON THE EDGE - BUILDING LONG TERM RESILIENCE IN RAINGARDEN PLANTING 32