This presentation was given at the 2019 Catchment Management Notwork meeting, which was held on the 11 October in Tullamore. All our local authorities and other bodies responsible for implementing the Water Framework Directive in Ireland attended to share knowledge and learn from each other.

1. UTLILISING GREEN INFRASTRUCTURE
Greening our towns and cities
A catchment-scale approach to achieving Good Status, reducing flooding and
mitigating the effects of climate change
John Stack, Senior Executive Engineer (A)
Dublin City Council

2. Question 1
What problem(s) are we trying to
address?

3. This Photo by Unknown Author is licensed under CC BY

4. Question 2
What, ultimately, is the cause of
the problem(s)?

5. Urbanisation

6. Impact of
Urbanisation
on Water
Cycle
Urbanisation fundamentally alters the way that water
moves through the landscape.

7. Urbanisation can be managed

8. ‘Urbanisation is NOT just the outward expansion of the city
Ave. 26m2
Paving front gardens:
c. 132,000 houses in Dublin
If 20% of these pave their front garden, that’s 686,400 m2
new impervious area
x
2.54 cm (1”) of rainfall
=
approx. 17,500 m3 additional runoff
(it’s over 87,000 m3 if they all do it)
Internal Urban Creep:
• Developing existing green
sites within the urban
area
• Paving front/back
gardens, extensions,
adding garden sheds, etc.

9. Urban Runoff is a major pollutant
National Urban Runoff Programme (NURP)
HEAVY METALS (CU,
ZN, PB)
NUTRIENTS AND
SEDIMENTS
COLIFORM BACTERIA OXYGEN DEMANDING
SUBSTANCES
EROSION AND SCOUR

10. Urban centres
Population
density
>10,000 >20,000 >50,000
Leinster 25 14 2
Munster 13 4 2
Connaught 4 2 1
Ulster* 2 0 0
*ROI only

11. Ireland to 2040
“…unmanageable sprawl of
housing areas, scattered
employment and car based
commuting, presenting…adverse
impacts on peoples’ lives and
the environment.”

12. Question 3
How do we allow for
sustainable urbanization?

13. Catchment-scale
stormwater
management
Using Green Infrastructure

14. Green
Infrastructure
“An interconnected
network of natural areas
and other spaces that:
1. Conserves natural
ecosystem values
and functions
2. Sustains clean air and
water
3. Provides a wide array
of benefits to people
and wildlife”
Benedict and McMahon
(2006)
• Green infrastructure is a
framework
• It’s applied at the large
scale, i.e. catchment
level
• It CANNOT be an add-
on

15. Green infrastructure
• Uses planning, design and implementation approaches
similar to those used for roads, water and wastewater
networks, and other critical infrastructure
• Highlights the importance of the natural environment
in land-use planning
• Recognises the importance of the management of
stormwater at source

16. Stormwater Green infrastructure
• US EPA expanded the term ‘GI’ to include the management of stormwater runoff at
the local level through:
• Natural systems, or
• Engineered systems that mimic natural systems
With the aim of treating polluted runoff
• Stormwater green infrastructure is more equivalent to green ‘best management
practices’.

17. Stormwater GI
• SuDS/SUDS, green BMP’s, etc.
• Natural and engineered systems
• Which integrate into the built environment
• Maximise stormwater as a resource
• Improve water quality
• Reduce flooding
• Provide a range of ecological, community, and infrastructure services
• A suite of technologies

18. Natural Water Retention Measures

19. Bioretention
and The
Stormwater
Chain
The Stormwater Chain
Source: Rain Gardens, Nigel Dunnett and Andy Clayden

20. 4 Elements of the
Stormwater Chain
• Prevention of runoff
• Retention techniques
• Detention facililties
• Conveyance techniques

21. Objectives of
Bioretention
Reduce the amount of
impervious surfaces in order to
reduce runoff
Utilise the landscape and soils to
naturally move, store and filter
stormwater runoff BEFORE it
leaves a site

22. Question 4
How can we:
• Achieve good status under WFD
• Mitigate flooding
• Maximise biodiversity and ecology
• Provide amenity needs for
community
• Facilitate compact urban
development and regeneration

23. Strategy comes first

24. Case Study: Morecambe Bay, UK

25. Example: River Channel Rehabilitation

26. Answering Question 4 for the
Santry Catchment
•A river restoration plan
•A catchment-wide stormwater
management plan
•Application of green infrastructure –
beginning with pilot locations

27. Governance
Multi-departmental, Cross-Agency
Project
Environment and Transportation
Flood Projects and WFD Division
Roads and Traffic
Culture, Recreation and Economic
Services
Parks and Landscape Services Division

28. Community engagement

29. Masterplan → sub-catchment plans

30. Street-scale

32. Individual Site: Clandeboye NS

33. For the householder
• Water butts
• Rainwater planters
• Rain gardens

34. Last Easter, I decided to build
a rainwater planter

35. I did some simple calculations

38. Outcomes from the effective
use of Green Infrastructure
• Reduces runoff volume, peak flow and
flow duration
• Slows down flow to increase the time of
concentration and encourage infiltration
and evapotranspiration
• Restores groundwater recharge
• Protect downstream water resources,
including wetlands
• Reduces downstream flooding and
property damage
• Reduces the frequency of operation of
combined sewer overflows (CSOs)
• Improves water quality by preventing
pollution from entering the watercourse
• Reduces thermal pollution
• Improves habitats, biodiversity and
ecology

39. When life gives
you rain…..

40. Thank you.