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Cape Town’s Stormwater PondsInvestigating the amenity that they
provide
Prepared by: Alastair Rohrer
Supervisor: Professor N.P. Armitage
2
Background to Stormwater Ponds
• What is a stormwater pond?
• Four
primarydifferent
functionstypes
of a stormwater
• Three
of ponds pond
Detention Ponds
Susdrain (n.d)
Retention Ponds
Alliance (2010)
Constructed Wetlands
Pendrake (2007)
3
Presence of Amenity
Definition:
Individual
Property in
affluent area
A feature or facility that improves the
comfort, convenience or the attractiveness
of an area
Detention
Pond
Why amenity important to stormwater
ponds?
(Google Maps, 2014)
Cape Town’s Current Situation
• Approximately 800
stormwater ponds
• Inadequate GIS
records
• Provision of amenity
unclear
4
Aim & Limitations of Investigation
Aim of Investigation
Limitations
of Investigation
•• Time
Deliver insight into if or what amenities are being
• Personal
safety
provided by
Cape Town’s ponds
• A single engineers perspective
5
Methodology
6
Locate and describe ponds
• Synthesis of three data sets through GIS software
Pond Investigations
• Individual ponds inspected
• Selection criteria
- Type of stormwater pond
- Size
• Investigation duration
six days,of
77area
ponds,
10% sample
- -Affluence
(Romanovsky
&
Gie, 2006)
- Aesthetic value
• Elements related to amenity
- Major catchment
- Evidence of maintenance
- Dual-use
- Negative amenities
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Aesthetic value
Nganga Township
Constantia Greenbelt
• Stormwater ponds pose a visual impressionVery
on their
Low
surroundings
• Ponds rated on aesthetic value
• Two components had the most significant impact on
aesthetic value - Type of stormwater pond
High Affluence
- Affluence of theDetention
area
Pond
Retention
pond
Low
Affluence
Multi-functional Stormwater Ponds
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• Most notable uses - Educational infrastructure
- Play parks
- Public open space
- Walking trails
- Sports fields
Uni-use detention pond
Play Parks
Public open
Sports
space
field
Multi-functional Stormwater Ponds
9
• Impact of type
of stormwater
pond?
affluence
of the area?
• Over 70% of retention ponds
and constructed wetlandsLow
affluence
High
affluence
incorporate multifunctionality
• Only 41% of detention ponds
incorporated multifunctionality
Educational Infrastructure
Walking Trail
Sports Field
Negative Amenities
• Common aspects that degraded the amenity present
– Infiltration
– Grass not cut
– Fencing
– Drowning risk
– Litter present
– Squatting
– Litter trap
10
11
Negative Amenity
100 60
90
80
50
70
40
50 30
%
%
60
Litter Present
Litter Trap
40
20
30
20
10
10
0
0
Infiltration
Very
High
Fencing
High
Drowning Risk
Middle Litter Trap
Affluence of Area
LowSquatting
Grass
Not Cut
Very Low
Litter Present
Negative Amenity
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• Numerous
aimed tofrom
cleanon-site
up litter
Abundanceprograms
of litter originates
dumping,
− Municipal
districts
teams
littering and
littermaintenance
entering the
pond from the
− Winter
readiness
program
stormwater
network
− Expanded Public Works Program (EPWP)
• Litter degrades the performance of all of the
− Educational Programs
stormwater pond’s functions
• Numerous programs aimed to clean up litter
Conclusions
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• Amenity helps improves the use of space
• Over 50% of the investigated ponds had a negative
aesthetic value
• 51% of the investigated pond showed evidence of
incorporating multi-functionality
• Litter is one of the most detrimental factors to
amenity within Cape Town’s ponds
• Many of Cape Town’s ponds are providing amenities
• There is room for improvement!
Thank you
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