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Contents
of June 1998
UPFRONT & OPINION
MILLENNIUM PUBLIC SPACES COMPETITION
INSPIRATION
INSULT
TREE OF THE ISSUE
FEATURES
Hennops River Catchment Management
Three projects at
Kirstenbosch:
- Botancal Society Conservatory - a naturally conditioned glass house
- Kirstenbosch Visitors Centre
- Landscape furniture enchancing the Kirstenbosch legacy
Clean water for Modderspruit
A constructed wetland in a highveld
garden
Rehabilitation a Wetland - Lenjane
Vryheid
Restoring the Wakkerstroom Wetland
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UPFRONT & OPINION
Sustainability in the Built Environment - a practical approach
This
conference, to be held at the MTN Dome in Randburg, is scheduled for 26 - 28 August 1998
and will run concurrently with the Interbuild Africa ' 98 exhibition.
Topics will
include life-cycle design and eco-labelling, energy efficiency and water efficiency in
buildings, green building materials, best practice case studies of sustainability in South
African buildings, case studies of informal settlement upgrades, planning and development
of housing and urban conservation and renewal; along with public and private sector
responses to the challenges and selected SA best practice applications of Environmental
Assessment.
Speakers
include: Dr Charles Kibert of the School of Architecture, University of Florida, USA; Prof
Dieter Holm and Roger Fischer of the Department of Architecture, Pretoria University;
Richard Hill of UCT; Steve Ballot, CSIR - Transportek; Prof Alan Mabin of the Department
of Architecture, Wits; and Chrisna du Plessis of CSIR, Boutek.
5th International
Botanic Gardens Conservation Congress
The
conference, which is held at a different venue every four years, is being hosted by the
National Botanical Institute (NBI) of South Africa and will take place at Kirstenbosch
from 14 - 18 September 1998. The conference will deal with issues facing the conservation
of plants in botanical gardens.
25th Congress of
the International Organisation for Succulent Plant Studies
The congress
is being hosted by the NBI in collaboration with the Succulent Society of South Africa, at
the Kirstenbosch VisitorŐs Centre from 31 August - 1 September 1998. There will be a
one-day excursion to the Karroo Botanical Gardens in Worcester and delegates will be able
to visit the new succulent conservatory at Kirstenbosch. Call for papers: contact Craig
Hilton-Taylor.
Urban design
short course
An
introductory short course on aspects of urban design will be held in Clarens in the Free
State from 10 - 13 September 1998. The course is aimed at practising town and regional
planners, architects and landscape architects, although it will also be of benefit to
related disciplines such as civil and transport engineers and leaders in local government
departments.The main aim of the course is to stimulate mid-career professionals with new
perspectives and ideas and to foster an awareness of urban design. Case studies will be
presented, backed by slide shows and followed by discussion. The sessions will be lead
largely by urban designers in private practice, local government or academia. Contact Louw
van Biljon.
Workshops:
integrating environment into Curriculum 2005
Environmental
literacy will be treated as a cross-curricular concern at all levels of schooling.
Participation workshops and the distribution of documents have attempted to address the
problem of teachers and teacher educators who have no training in environmental education.
Continued support of these teachers will take the form of a series of capacity building
workshops throughout the country. Resource materials based on the first series of
workshops held in the Northern Cape will be published soon.
Environmental
concerns given true priority: Atlantic Beach Golf Course
The Atlantic
Beach golf course, presently under construction, is in Melkbosstrand on the Cape West
Coast. Landscape architect Anthony Wain of the Planning Partnership, who was reponsible
for the Environmental Management Plan (EMP), comments on the project: "The art and
science of developing a top quality golf estate in an environment such as this lies in
working with the genius loci or the spirit of place to protect and enhance the natural
assets. The golf course lies in a landscape which could itself have been designed for
golf."
An
independent Environmental Impact Assessment (EIA), done by consultants Crowther Campbell,
identified the natural opportunities and constraints - and the layout of the estate is a
direct response to the findings of the EIA. The client, Johnnic, then commissioned the EMP
which extended the findings of the EIA into a practical environmental strategy for day to
day use on site. About 50 % of the fynbos on site is derelict, badly invaded by alien
vegetation, and a major clearance programme relying on chainsaws and a chipper, chosen for
minimal environmental impact, is underway. This is being followed by extensive
revegetation.
The more
sensitive areas of fynbos have been avoided or incorporated into the out-of-play areas of
the course or integrated into the residential areas as open space. The golf course
designer and contractor, Mark Muller of Golf Data, says that because fynbos has a low
carrying capacity and does not regenerate easily, a golfer whose ball lands beyond the
knee-rail fence, which demarcates the fairway edge, will have to drop another ball and
will be strongly discouraged from going in search of the lost ball. Both the fairway and
the greens' grass is selected from Cynodon species which are indigenous to South Africa
and are low water users.
Energy and
water saving technologies are being investigated for the residential units on site, with
the possibility of double plumbing to allow for the use of grey water, while an
environmentally sound waste disposal strategy is also being researched. All the workers on
site have attended lectures on the EIA and EMP processes, including the sales staff who
are then better able to sell the "added value" of the natural environment on to
the end user.
Inanda House provisionally declared a National Monument
According to Dr Johann Bruwer of the National Monuments Council, this is the first
residential garden, with a predominance of South African flora, to be declared a National
Monument in the country.
Sydney and
Victoria Press started creating this extraordinary garden in 1955, on the site of an old
fruit farm with a farmhouse designed by Herbert Baker. Over the years design input was
given by a number of renowned landscapers such as Patrick Watson, Joan Pim and Roberto
Burle Marx. Watson, who was involved with the garden for close to 20 years, said of Press
that he was an international connoisseur of plants. It is a garden of wonderful, bold
vistas and precise small details, comprising a collection of plants akin to a botanical
garden. (See article in Nov/Dec ' 97 issue of The Urban Green File).
Inanda House
has been provisionally declared a National Monument for a period of six months to allow
for negotiations concerning the long term conservation of the property, which is up for
sale, at present. Herbert Prins, also of the Monuments Council, said the reasons for its
declaration were that it was firstly a garden of great artistic value and secondly that
gardens with large indigenous components were part of the cultural history of the country.
He said that the garden was one of the finest in the country, maybe even one of the great
gardens of the world. Bruwer added that its value as a green lung in an urban area was
also relevant.
South African
Manual for Outdoor Advertising Control
SAMOAC,
which is based on a research project undertaken by Willem van Riet (at the time Prof of
Landscape Architecture at Pretoria University) in 1994 on behalf of the Department of
Environmental Affairs and Tourism and the Department of Transport, was officially released
at a function in Pretoria on 7 May 1998.
Numerous
interested and affected parties were consulted in the development of the manual. It is a
colourful document, loose leafed so that it can be easily updated, and user-friendly. (See
article"Outdoor Advertising: an urban art form or visual pollution?" in Mar/Apr
issue of The Urban Green File).
ISO 14000 posters
and brochures
The
Department of Environmental Affairs and Tourism (DEAT) has published a set of brochures
and posters for the business community on the ISO 14000 series of Environmental Management
Standards. The first brochure is an introduction to the ISO 14000 series of standards,
while brochures two to six cover: Environmental Management Systems, Environmental
Auditing, Life Cycle Assessments, Environmental Labelling (Eco-labelling) and
Environmental Performance Evaluation.
Contact
Mienie van Vuuren of the Industrial Environmental Forum for copies of this user-friendly
series or information about contact persons in your area.
Debate: VODAWORLD
In response
to our article and Heinrich Kammeyer's critique on Vodaworld in the March / April issue
(page 21), The Urban Green File asked three designers to debate the architectural and
environmental merits of this development. Is Vodaworld a truly futuristic building or just
another shopping mall?
Much has
been made of the "futuristic" design of Vodaworld in Midrand. It is a relief
that, just for once, we have been spared more colonnades, pediments, quoins, and fake
stone details. As a departure from the neo-classical mould, Vodaworld is indeed
commendable in the developers" battlefield of mediocrity in Midrand. But that does
not make the project "futuristic" or "new".
The
architects have, by their own admission, found their task challenging because of a lack of
precedent for reference. I would beg to differ. Not too long ago, the same architects gave
us another shopping centre, themed and tarted up, with a large collection of look-alike
shops. A visit to the now-not-so-fashionable Randburg Waterfront will convince. Is
Vodaworld perhaps simply another tarted-up box, a decorated shed like thousands of others?
It is a shopping mall in the veld, an internalised world of its own, shouting for
prominence, and containing dozens of shops competing for the same clientelle. So much for
precedent.
It is not
futuristic either. How should this be defined? Is futuristic architecture anything that is
clad in aluminium rather than face brick? Is futuristic architecture any building that
contains new technology? Why then do Internet provider companies seek out the worst
neo-classical office blocks for their own premises? Why do cellphone manufacturers live
alongside them in the same theme parks of retro design? And as for the form language - I
can remember a few Japanese art museums of the "70s that display very similar forms
to Vodaworld. So where is the edge? This is not a new departure in architecture, either.
If the history of architecture in this century can be described as a continuing search for
dematerialisation, for dissolving the solid and linking interior to exterior, the
internalised "black box" of Vodaworld is indeed retrogressive rather than
futuristic. And this sad fact is not redeemed by flying-sails of fabric sunscreens or by
fibre-optic lamp-posts.
Vodaworld is
not exceptional. Vodaworld is simply very fashionable, as evidenced by its
"techno" signage. It is current and flashy, has a very ' 90s curvaceous
"feature", much like the latest model of cellphone. It is as self-referential as
any other building along that highway; it is inscrutable and does not share any of its
inner life with the outside - much like any other neo-classical office block. It has been
styled for impact, and interestingly so. The "rear facades", those faces
normally disregarded by the designer, are similarly haphazardly treated; only this time
they face north and south. And they are visible at high speed along the highway, and more
prominent than the expensive aluminium cladding.
But to be
fair, using the building is an interesting experience. The interiors create an almost
delirious effect, coupled with the lack of orientation resulting from limited signage. The
separation from the bright, generous, natural exterior to the highly synthetic, stylised,
games arcade-like interior is startling and numbs the senses for a moment.
As for the
nine-hole chip-and-putt, I can think of no worse way to spend a "wait for a
cellphone" than to putt vainly between office blocks and parking lots. But then
again, visitors to the Waterfront chip balls from a shopping arcade across a puddle of
brackish Transvaal river water... the attraction lies in the fantasy generated in the mind
of the consumer. Only truth is stranger than fiction. And so we watch with amazement the
strange fringe suburban activities of consumers as they latch onto the possibilities of
this "futuristic" shopping centre and its fantasies. But like a dated science
fiction novel, the reality of Midrand is much more entertaining than the
"future" which Vodaworld purports to evoke.
"The
landscape design complements the architecture"
-
Danie Rebel (Gouws Uys & White - landscape architects for Vodaworld)
The merits
of the architecture and landscape at Vodaworld can only be debated when they are seen as
one integrated environment and not in isolation of each other. Vodaworld functions as a
shopping centre for hi-tech, modern communication technology. The use of metal, stainless
steel, canvass sheeting and large white surfaces makes a strong statement in a modern
developed highway environment. These not only make an impact on high-speed travellers but
also on visitors who experience a world of technology and contemporary architectural
detailing.
Landscaping
at Vodaworld comprises a mass parking area landscaped with 160 trees and 10 000
groundcovers, so as to create a forest in the long term - linking the built and natural
environments. The question is raised about how this design relates to the Highveld
environment? The indigenous Dietes (wild iris) groundcover in the parking area resembles a
grassland. The forest, comprising plane and camphor trees, responds to the colour of the
built environment (white and green). Primarily, it adds maximum vertical scale in the play
between the built and the natural environments, which are not in competition but support
one other.
"The
internalised building provides a captive audience for the products and services marketed
within."
-
Rodney Grosskopff (MHGL - architects for Vodaworld)
This area of
Midrand is largely undeveloped with no existing architectural context. However, Vodaworld
does respond to the highway context and the specific site was chosen for its prominence
and visibility from the highway. Its futuristic appearance is in keeping with Midrand's
image as a new, hi-tech modern city, as well as the language of the information age (cell
phones, satellite communication and computer technology).
The interior
and exterior are indeed worlds apart and not strongly integrated. The building is largely
internalised, purposefully so, to form a protected shell against the noise of the highway.
The suggestion has been made that the building could have been linked to the golf course,
with the coffee shop overlooking the course and even with an outside seating area.
However, the coffee shop serves the purpose of an interior waiting room. The original
concept was to provide a large waiting room serving the same purpose as that in a doctor's
consulting rooms - the patients being cellphones. We suggested the provision of coffee
vending machines for this space and finally decided on a full scale coffee bar. It is
inside, flanked by the various shops, so as to provide a captive audience for the various
products and services on sale.
The golf
course forms a separate entity because the building was already designed by the time the
decision was made to develop the course on the neighbouring property. It was the
developer's intention eventually to build another building on this property. However, the
thinking at the moment is to retain the golf course as a green lung and develop along the
opposite side of the course.
Although
Vodaworld may at present be a building surrounded by a sea of parking bays, the
development of the neighbouring properties, will result in an integrated precinct with
Vodaworld at the centre. Vodaworld is a world first, one stop, cellular service centre. It
is a fantasy world of unique architectural details showcasing the exciting technology for
which the late 20th century will be remembered.
-----
MILLENNIUM PUBLIC SPACES COMPETITION
The Urban
Green File and Townscape are sponsoring a competition for those who manage and / or own
public open spaces within urban areas.
Who should enter?
Local governments (municipalities), provincial and national government
departments, public or community organisations, landowners, developers and tertiary
education institutions who manage or own a public open space (park, square, street, campus
or nature conservation area) within an urban area. Consultants are precluded from entering
but are encouraged to motivate landowners to enter if they are involved in an appropriate
project.
The
following categories will be contested:
•
larger parks (regional
or metropolitan parks, > 1 ha)
•
'pocket parks'
(smaller parks, < 0,5 ha)
•
squares and streets /
malls
•
nature conservation
areas
•
campuses (tertiary
educational institutions)
•
parks and conservation
areas charging an entrance fee (e.g. botanical gardens)
Entry forms are available from The Urban Green File at Tel: (011) 888 6865. The closing
date for entries is Friday 17 July 1998 at 5 pm. Entries must be delivered to 10 Victory
Road Greenside, Johannesburg. Entries must be mailed to: P.O. Box 922 Parklands 2121.
Townscape Millennium Public Spaces Competition is sponsored by Enviro Elements /
Townscape, Tel: (011) 622 8820.
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INSPIRATION
Some pleasing ones
The
Urban Green File is delighted to be able to give this issue's "Inspiration
Award" to a series of billboards!
These are
built into the Campbell & Thiselton building which is visible from the "concrete
highway" in Sunninghill, Sandton. The company imports and manufactures perfumes and
large, stylish adverts of some of their products are built into rectangular arches, which
have clearly been designed for this purpose.The idea is simple and fairly low key and so
are the adverts, yet they attracted my attention immediately. What a great idea - not
unlike, and yet not as provocative as (or done with the same integrity as), Edgars City in
Johannesburg where "...the blank precast facade panels have disappeared under a new
skin of oversized fashion billboards..." as Henning Rasmuss said in his article on
this building, which should be declared joint winner of this issue's Inspiration Award
(Nov/Dec ' 96 issue of Green File).
Billboards
or, more accurately, large posters that are part of existing functional structures, are so
much more aesthetically valid than the monsters that stand alone, arrogantly defacing
residential areas and even areas of countryside, on their ugly steel pedestals - as our
"Insult to the Environment" depicts. Another, quite acceptable, in fact,
stimulating utilisation of huge, brightly coloured posters is on the sides of the
Woolworth's trucks - the "Berried Treasures" advert for the Woolworths range of
fresh berries, with its rows of succulent fruit, is my favourite. It also makes good
advertising sense because these trucks move and are continuously displaying their adverts
to different people in different locations..
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INSULT
And some hideous ones!
The poor
commuter from Johannesburg to Pretoria is exposed to the Shell billboards every day and
they become meaningless, very quickly (after the bilious feeling leaves him).
I find it
difficult to reconcile the excellent work that Shell does in the environmental field -
winner of the 1996 Green Trust Environmental Entrepreneur Award for their development of
environmental education resources - with their complete lack of understanding of what
comprises visual pollution. We think the problem might have arisen with the large new
Caltex signs up the road at the Star Stop, which we reported in our Jan/Feb '97 issue, and
that Shell Ultra City felt they had to compete with something much bigger and more
dramatic.
"We
have to choose, because a hundred million impulses pour down on our nervous systems, and
if we accept them all, we will soon be overwhelmed and die in confusion. Of all the
millions of incoming signals, only a small number reach the brain and a still smaller
number get passed on to those areas where they can give rise to conscious awareness. The
chosen pieces are not necessarily the most dramatic stimuli - the loudest sounds or the
brightest lights; very often they are subtle changes in the environment made conspicuous
only because of their incongruity." Lyall Watson, Supernature
-----
TREE OF THE ISSUE
Ilex mitis
Commonly
known as African Holly
The choice
of the tree for this issue has been made by Linda De Luca of Random Harvest Indigenous
Nursery in Muldersdrift, Gauteng. She calls Ilex mitis "a majestic evergreen",
with its dark green foliage, prolific displays of shiny red berries, that the birds love,
and masses of lovely white flowers clustered along the stem. "The new foliage is red,
while older leaves often retain red tips and edges, with reddish leaf stalks, adding
another dimension to the dark green foliage. Landscapers should remember that the trees
are either male or female and if the intention is to attract birds, it's necessary to
plant several trees,"says Linda. The tree needs to be well-watered, although it will
tolerate quite dry conditions - under such conditions it doesn't reach a large size. It is
a useful tree for seasonally wet areas, as it tolerates damp to marshy conditions during
the rainy season. Linda says that Ilex mitis is a truly frost-hardy tree.
It always
keeps its shape which makes it an ideal landscaping subject. "I have found that from
a very young stage, in the nursery, Ilex has a round shape. It almost grows as a standard
and the shape never changes. In warmer areas, where the tree grows faster, a long
centrepiece grows out at a young stage, but it soon reverts to its round shape. It never
gets untidy. It makes an ideal avenue tree and can be used in parking lots, but only when
it is irrigated - because the heat reflects off the hard surfaces creating fairly dry
conditions," comments Linda. " It is an ideal tree in a grouping of three to
five on a stretch of lawn."
Ilex mitis
is indigenous to a large portion of South Africa from the Northern Province, through
Gauteng and Mpumalanga and in a broad band down the eastern part of the country, right
down to the Western Cape. It occurs naturally in shady forests near water. Linda says that
it grows relatively fast in Gauteng from between 0,5 - 1 m annually, depending on
conditions. It grows fast when it is young and slows down as it grows older. Asked to
comment on the vast size of the tree in the adjacent photograph, she said that there were,
obviously, ideal shady forest conditions in that part of the Kirstenbosch Garden and that
in such a protected, frost-free environment, and probably over many years, this tree has
reached a good height (between 20 - 30 m). She said that it was conceivable that the tree
could grow to this height, under sheltered forest conditions, in some kloof in Gauteng.
-----
FEATURES
Will Catchment Management save the
Hennops?
The
seriously polluted Hennops River illustrates a lack of holistic catchment management. However, various projects
areunderway to improve the water quality and make the river's embankments accessible as a
public recreational space.
As a
seriously polluted river system, with some areas rendered unfit for human interaction, the
condition of the Hennops River illustrates the consequences of a lack of catchment
management.
The river
originates towards the east of Johannesburg and south-east of Pretoria, with the
Kaalspruit and Sesmylspruit forming its feeder streams. The river system is the
responsibility of a number of local authorities, making co-ordinated planning and
management difficult. The Kaalspruit is mainly the responsibility of Tembisa-Lethabong and
Midrand (local councils within the Khayalami Metropolitan Council). The Sesmylspruit falls
under the auspices of Pretoria, and the well known Rietvlei Dam is in this area.
Downstream of the dam, the river is known as the Hennops and is the responsibility of
Centurion
The Urban
Green File followed the course of the Hennops and its feeder streams and reports on some
of the initiatives underway to remedy the unacceptable conditions for which this river is,
unfortunately, known.
Kempton Park-Lethabong
- Pollution Control Strategy
Many of the problems downstream, such as the silting-up and severe pollution of
Centurion Lake, can be attributed to the conditions upstream near the river's source. Not
only do the dirt roads of Tembisa erode during heavy storms, thereby adding silt to the
stream, but the sewer pipes drain towards the low lying river course. Tembisa's main sewer
follows the river course and this pipe often becomes blocked with sewage overflowing from
the manholes into the river - a major cause of pollution with a resultant health risk.
However, the
Kaalspruit Co-ordinating Committee, initiated by the Khayalami Metropolitan Council (KMC)
during October 1996, has formulated a pollution control strategy to improve the river's
condition. The strategy comprises the beautification of embankments, removal of solid
waste and regular monitoring of the water quality. Xola Nzo of the KMC explains the
council's approach: "We view open spaces as a valuable asset to our city. We cannot
just build houses in isolation of other social needs. The community needs open spaces as
well and the Kaalspruit presents the opportunity to incorporate nature into the
city." Environmental education, he says, remains a problem - the community needs to
be educated about the real benefits of such a natural system.
The KMC's
capital budget for the next financial year provides more than R 2 million for the
Kaalspruit - this include consultant's fees, disaster management, health and environmental
awareness campaigns, development of a pollution control strategy, open space development,
"spruit development" and a water and sanitation strategy.
Midrand - Open Space
Plan
The Department of Environment and Recreation Management (ERM) at the Midrand
Metropolitan Local Council has appointed Gouws Uys & White to prepare an open space
plan for the Kaalspruit. This study is currently in progress and its suggestions will have
to be ratified by the council before implementation.
Some of the
problems which the study has identified are:
•
The random dumping of
domestic waste, sewage, dead animals and even industrial waste is, sadly, viewed as a fait
accompli practice by the surrounding residents.
•
Land encroachment by
informal settlements occurs along the spruit and renders potential open space nodes and
activity spines unusable for future planning.
•
A lack of awareness
exists about the environment as a potential resource for the fulfilment of basic
recreational needs within the community.
Although a
lot of the pollution originates in the Kempton Park-Lethabong area and has to be dealt
with at source and on a regional level, the study recommends the construction of a series
of wetlands or natural reedbed filters below the Ivory Park catchment area so as to
minimise the pollutants entering the stream. The water in these wetlands could also be
"recycled" for irrigation purposes following an example in Beijing, China, where
reedbeds are used to treat sewage along the watercourses. The flood valleys are then
utilised as production units where vegetables, fruit and rice are produced within the city
limits.
Furthermore,
according to the report, a natural wetland in the Clayville area is under threat and
should be rehabilitated. At present, stormwater discharge from this industrial area is
causing severe erosion problems - the area is reverting to dry grassland because water can
no longer spread out from the deeply eroded channel.
The Open
Space Plan envisions the transformation of the Kaalspruit river system into a cleaner,
safer environment with passive and active recreation areas for the Ivory Park community.
It also suggests an urban agricultural component where the surrounding community would
become involved in educational programmes concerning agricultural and horticultural
techniques so as to cultivate their own crops.
Rietvlei Dam
Both the Kaalspruit and the Sesmylspruit flow into the Rietvlei Dam in the
Pretoria area. The dam supplies part of the cityŐs drinking water and is located within a
nature reserve - the reserve was proclaimed to protect the many springs in the area.
Waterlab Research and GFJ Consulting Engineers have recently completed a study into the
environmental and hydrological aspects of the Rietvlei Dam catchment area. The study
comprised a monitoring programme of the water quality, the fish population and the
invertebrate fauna between 1994 and 1998. It found that sewage effluent was being released
into the catchment area at approximately 14 million m3/a, and this together with an
increase in the volumes of treated sewage effluent entering Rietvlei Dam from the Rietvlei
Water Treatment Plant, had caused an increase in the amount of plant nutrients and other
major cations and anions reaching the dam
The report
states: "During the mid 1970s, Toerien & Walmsley (1979) described Rietvlei dam
as nitrogen limited (N:P ratio <7:1), which favours the growth of nuisance blue-green
algae such as Anacystis sp (Microcystis sp) and Anabaena sp. During that time, Rietvlei
Dam had already been described as critically eutrophic. Currently, the situation is
significantly worse, with Rietvlei dam still being nitrogen limited, and experiencing
nuisance conditions (high algal growth) 68% of the year. Not only do these algae produce
nuisance conditions for indirect water sport activities such as angling and yachting, but
the situation also results in major problems (tastes and odours) with potable water
treatment. Additional environmental problems regarding the general ecology of the
catchment and Rietvlei Dam are also experienced."
The study
recommends alternative ways of advanced water treatment and a committed water quality and
environmental management plan for both the dam and the catchment area. Two new projects
have already been initiated - a peat bank / natural wetland area which was drained by the
beginning of this century is being restored and allowed to be flooded again. A fish
breeding programme in conjunction with the University of the North is also in operation
with the aim of re-introducing "Klein Skulpgeelvis" into the dam.
Centurion Lake -
proposal for an artificial wetland
Centurion Lake is located downstream of the Rietvlei Dam and forms the focus of
Centurion City - a public open space surrounded by retail and office facilities. The edge
of this man-made lake is fully concreted and the water retained by a concrete dam wall.
Originally, this lake was well utilised for water sports and its famous musical water
fountain was a major attraction. However, due to severe pollution upstream, Centurion Lake
has become the collection point of silt and other waste. The situation is so severe that
the lake is almost completely silted up and the water is not deeper than 500 mm at any
point.
The water is
currently being treated with natural bacteria, as opposed to chlorine which would damage
the ecology downstream, to eliminate the sludge and bad odour. The council also purchased
a dredger, a few years ago, to remove the silt from the lake. However, this method proved
to be very time-consuming and not cost effective at all. The alternative solution,
proposed by a team of consultants, is currently the subject of a pending court case.
The council
has approved the construction of an artificial wetland in the nearby Highveld Techno Park
and a pipe has already been constructed leading from the lake to this area. Silt will be
pumped from the lake to the wetland which will act as a "slimes dam" and the
area will be developed as a visual attraction with bird hides and board-walks. Not only
will this solve the problem at Centurion Lake, but it will also provide another public
open space and an area rich in ecological diversity for the benefit of the town. However,
residents are adamant that they do not want a"slimes dam"in their
"backyard" and they are opposing the development.
The
situation at Centurion Lake must be one of the most pressing issues in the Hennops River
catchment. The situation illustrates the need for rivers (and catchment areas) to be
managed holistically as opposed to the fragmentalised planning by different local councils
which is the order of the day. The Khayalami Metropolitan Council's involvement at a
regional level is a step in the correct direction. Limiting pollution upstream, near the
source, will alleviate the problem downstream in Centurion. However, the silt in the lake
has to be removed so as to prevent the problem from escalating downstream.
Already,
immediately below the lake, mature indigenous trees are collapsing into the river (see
Insult, The Urban Green File Jan/Feb 1998, p 21). Because the river is silted up and
shallower, the water is carving away the embankments to compensate for the loss of space.
The Urban
Green File wishes to acknowledge Gouws Uys & White and Waterlab, both of whose reports
were generously borrowed from this article (see references).
References:
The Urban Green File has compiled a list of references and contacts regarding
information available on the Hennops River catchment area.
Reports and Studies:
*
De Wet,
L.P.D. Enviornmental and Hydrological aspects of the Reitvlei Dam Catchment Study. 1998.
(Contact Waterlab at Tel: (012) 3491072).
*
Environmental
Evaluation of part of the Hennops River. 1995. Ekokkonsult and Loubscher Human. Lombart
Consulting Engineers. (Contact Eddie Goister at Cel: 083 441 2611).
*
Hoffman,
J.R. Non Point source pollution in the Hennops River Valley. 1995. WRC Report no 518/1/95.
(Contact the Water Research Commission at Tel: (012) 3300340).
*
Kaalspruit
Open Space Master Plan - Draft report for the Department of Environment & Recreation.
Management, Midrand Local Council. (Contact Gouws Uys & White at Tel: (012) 6631045).
*
Management
of urban impoundments - National register of urban impoundments in South Africa. (Contact
the Water Research Commission at Tel: (012) 3300340).
*
Toerien,
D.F. & Walmsley, R.D. The chemical composition of the upper Hennops River and its
implications on the water quality of Reitvlei Dam. 1979 Water SA, 5(2): 77-89.
Useful Contacts:
*
Wates Meiring Barnard
- Consulting engineers for the Centurion artificial wetland. Tel: (011) 315 0316.
*
Mr Bouwer -
Responsible for the Kaalspruit at the Midrand Council. Tel: (011) 3144997.
*
Xola Nzo Responsible
for strategic planning on the Kaalspruit at Khayalami Metropolitan Council. Tel: (011) 394
7424.
*
Willem van Reit -
Although not directly involved with the Hennops River, he has wide knowledge of the
hydrology. of the catchment area. Tel: (012) 3483292.
-----
Ecological
Arrangement in a naturally conditioned glass house
The main
purpose of the Kirstenbosch glass house is to display the rich diversity of our succulent
species - over one third of the world's succulent species occurs in Southern Africa.
The largest
portion of the glass house is devoted to a collection of plants from the arid zones and
this makes it a unique structure, of its size, as most of the world's conservatories are
devoted to tropical and sub-tropical flora. Project architect Julian Elliott, who designed
the building in association with MLH Architects, has a keen interest in glass houses and
had travelled to the US and Europe on an annual basis to collect information, for many
years prior to being commissioned for the Kirstenbosch project.
At Flora '
93, the model and plans for the glass house were exhibited and Kay Bergh, then president
of the Botanical Society, spearheaded a fund raising campaign which resulted in a number
of key donations. The National Botanical Institute then came on board and further
donations followed as a result of director Prof Brian Huntley's efforts. In 1994,
Kirstenbosch horticulturist Ernst van Jaarsveld, who had spent 20 years working with arid
Karroo plants, was asked to undertake the planting design. He used a holistic approach,
not only grouping the plants ecologically, in conjunction with rock types from their
native environments, but orientating the plantings according to natural distribution so
that those from the northern parts of the country were located on the northern side of the
house. The building was completed in January 1996, but it took a further year to install
the plant material - a substantial amount of which was already in the greenhouses of
Kirstenbosch.
The three
planning studies for the garden, done over a number of years, all recommended, from a
logistical point of view, that the lower precinct be zoned for a conservatory and that
built structures in the middle garden be minimised - because the number of visitors far
exceeded the capacity of the adjacent existing parking lot. Although the visual impact of
the large, triple-pitched glass structure is minimal from the main road, Elliott mentioned
that the glimpses of the house were enough to entice the visitor to explore further,
whereas the low siting of the house made it completely invisible from the garden.
The shape of
the glass house, which has an overall area of 1 695m2, was dictated largely by the
intention of creating a naturally conditioned structure. It is positioned and orientated
(facing slightly east of north) so as to derive maximum benefit from the sun, and designed
to provide ideal display conditions - while the vast cascading roof of 1 518 m2
attracts the most light in winter at midday, it reflects the sharp early morning and late
afternoon rays in summer, as these are the ones that are most likely to damage plants.
The large
Camphor trees, in the adjacent renowned Camphor Avenue, shade the house from the western
sun. The laminated glass is tinted, and slightly more heavily tinted in the triangular
gables, as a further protective factor and, finally, there are blinds made of a very
stable fabric which can be dropped to shade the western side. The volume and shape of the
roof allows for maximum ventilation but should the temperature exceed 280C,
thermostatically controlled, hydraulically operated, roof windows will open automatically,
and if it builds up to above 330C, a back-up system of fans comes into operation. An
automatic gauge measures wind velocity and closes the windows when the wind reaches a
certain speed. Three of the four sides of the house are open to the outside air, covered
only by bird screening (a fine mesh wire), to create an effective through-draft. Van
Jaarsveld commented that the natural air drainage had been so successful that the fans had
not come on at all, as yet, and he predicted that they would never be necessary. "I
visited the Estufa Fria glass house in Lisbon, on the suggestion of Professor Lewis of
UCT, because they have a dry section. We learnt a lot about the need for air movement from
their experience - they haven't paid enough attention to the requirements of the plant
material. The place gets stuffy and the plants are inclined to deteriorate," said
Elliott.
The main
room or arid house is 548 m2, while the four corner units which comprise four
different plant environments - arid for the dwarf succulents, cool for both the bulb and
alpine houses, and humid for the fern and orchid house - are 90 m2 each. The
fernery, which is always protected by the fabric blinds, and afro-montane units have
artificially controlled environments, for most of the year, while the large arid house has
been provided with underground heating for the cold winter months but is naturally
conditioned for most of the year. The underground heating coils are also thermostatically
controlled and will only kick in on the very coldest nights.Elliott commented that there
were not only four different plant environments necessary bu"climatic"variables
(sun, heat, humidity and ventilation) that had to be contended with - and the four
seasons: "There were a lot of permutations we had to cope with." Peter Schuman
of MLH was responsible for the technical aspects, in conjunction with the
mechanical/environmental engineer, Marius van der Vyfer.
The design
of the interior serves as a background to the display. Local quartzitic sandstone, laid by
the stone masons of Kirstenbosch, has been used as much as possible, echoing its extensive
use for paving, steps, kerbing, walls, bridges, etc, in the garden - and providing the
warm buff colour as an appropriate natural backdrop to the succulents. All the colours in
the house are muted. The central house is organised in a spiral formation of planting beds
anchored by the 6,5 tonne baobab (the largest of all the succulent plants on earth) which
was donated by Venetia Diamond Mine in the Northern Province. Van Jaarsveld said that,
aside from its practical function to provide ramping for wheelchairs, he found the
spiralling pattern - the concept of Michelle Sandilands of MLH - very pleasing as it was
an organic shape which represented the many spiral formations in the micro and macro
cosmos: ...the spiral aloe of Lesotho, old inflorescences of proteas, the snail shell, the
milky way.
"The
glass house can be likened to a cathedral. A cathedral has an ambulatory which goes all
the way around its periphery and there are four little botanical chapels in the four
corners. Visitors can take the alternative masculine route, with a quick sprightly action,
up the steps, or make use of the gentler more feminine way which winds upwards in an
effortless climb without any steps, and provides an opportunity to survey the scene,"
said Elliott. He added that the lines of the geometric spiral were still very obvious but
that these would be softened as the plants grew.
Regions
represented in the arid house include the succulent Karroo (Namaqualand, Richtersveld,
Knersvlakte and Little Karroo), the Nama Karroo and Namib Desert (Karroo, Bushmanland,
Tanqua Karroo and parts of Namibia) and the dry bushveld regions ( KwaZulu-Natal,
Mpumalanga and the Northern Province). The plants include common species and the rarer
endemics. Van Jaarsveld has made use of natural rocks from each region and the soil of the
region, in the form of a shallow topdressing. Fifteen journeys were made to collect the
rocks and plants.
Speaking
about the maintenance of the plants, Van Jaarsveld commented on the importance of
separating succulents from the winter and summer rainfall regions. He said that some of
the dwarf succulents (Argyroderma and Lithops) were so sensitive that an extra drop of
water in their growing season would cause them to split open, risking possible fungal
infection. Everything is watered by hand.
"We
have drawn up an operations manual for the house, in which there are no rigid rules. It is
a matter of experience - knowing which plants are active in which seasons and looking at
the condition of the plants. The key to maintenance is constant attention. The bird
screening keeps the birds out but allows insects into the arid house, as we need the
natural predators. We have brought in the predatory mite to deal with the occurrences of
red spider mite on the baobab. Reptiles have moved in and the Cape skink is very effective
at controlling insects such as grasshoppers and beetles which cause real damage. This
system of largely natural control means that we need to do minimal spraying - we are
striving for a completely natural system," concluded Van Jaarsveld.
Kirstenbosch Visitors
Centre
Critique by Peter Dayson
My first impression on approaching the new Visitors Centre at Kirstenbosch,
once again re-inforces my hypothesis that Cape Town continues to lead the country in
architectural design, having eschewed the post modernist, neo-classical claptrap that
presently pervades Johannesburg, by developing a vernacular that reflects both the
sub-continent and the time!
A series of
beams, sloping roofs and pergolas progressively lead one from the parking area into the
courtyard, which itself is flanked by a pergola, visually leading one to the Glass House
beyond. The simplicity of line, muted colour and subtle detail both enhance and complement
the focal point of the Glass House. However, the absence of greenery, apart from the very
narrow beds against the external columns, on the exterior, brings into question the
relevance the botanical garden setting had in the architect's design philosophy. Whilst
one would not want to see a botanical collection detracting from the clarity of structure,
the height of the entrance could certainly have been broken with a series of planters and
planting with an architectural bias. The flow into the courtyard is also disrupted by an
information desk and a row of revolving and opening doors. The purpose of the latter is
difficult to fathom as this does not serve as a control point. Incorporating an
information kiosk into the courtyard and relating the restaurant, which presently
overlooks the parking and the main road, to the courtyard, would have added a very
necessary vibrancy to what tends to be a lifeless space.
The
architectural detail in the courtyard, with its muted colours and choice of materials,
gives the Centre a distinctly African feel but the absence of planting, once again,
ignores the setting. Purely from a practical point of view, one would think that selected
tree groupings would have provided visitors with an appropriate shady canopy. At present,
the lack of this, coupled with the noise of the water feature, does not exactly invite one
to linger. I also found the scale of the water feature incompatible with the space. Fewer
spouts, set at a lower level, with a larger diameter, would have been less noisy and more
visible from the entrance to the courtyard. Returning to the detail of the courtyard,
there are several points which are noteworthy. The general use of materials - the cut
slate, choice of brick and aggregate pavers, the wood and steel, all complement each other
to form a subdued and harmonious whole. One hopes that the recent addition of the
soapstone sculpture is a permanent feature. The security grille at the ticket office is
striking, as are the hanging baskets which are sculptural elements in themselves. The
attention to the detailing of the steel and cable railings means that these integrate
perfectly with the wooden columns and retaining walls. Larger pots, however, would have
been more in scale with the setting and creepers on the pergola would have softened the
space.
Apart from
the siting of facilities, especially the restaurant, the Visitors Centre should be an
asset to Kirstenbosch. My criticism tends to be more landscape architectural in nature and
perhaps highlights the absence of such an individual from the design team.
Landscape furniture
enchancing the Kirstenbosch legacy
Landscape Architects and Environmental Planners have prepared a Landscape
Furniture Design Manual for Kirstenbosch National Botanical Garden in Cape Town.
The
development of the garden since the early 1900s, starting with the "Dell" and
"Matthew's Rockery", provided a legacy that has been embroidered on and altered
over time. The first hard landscape materials were the gravel access roads, cobbled
pathways, flagstone steps - and some Batavian bricks around Colonel Bird's Bath, as the
jewel in the crown. The simple, timeless qualities of these few natural materials extended
later to the introduction of asphalt, cement roadstones, precast kerbs, brick and timber
decking, along with a host of accessories.
The more
memorable features of the man-made landscape, however, remain the dry-packed sandstone
walls, intricately cobbled paths, thatched shelters and teak gates. The challenge will be
to integrate appropriate new materials and forms with the older themes, so that the
Kirstenbosch legacy is enhanced rather than eroded.
It was felt
that a manual of design guidelines for all the hard landscape elements of the garden was
necessary to ensure a more comprehensive and co-ordinated approach to the provision of
paving, steps, walls and site "furniture" in general.Landscape furniture
includes a wide range of components - bollards, litter bins, benches, railings, signage,
lighting, bridges, shelters and kiosks. Except for the signage system, which was the focus
of a special project, most of the elements have been installed on an ad hoc basis over the
years.
In the 1973
Development Study for Kirstenbosch, Fagan recommended that the landscape accessories be
considered collectively, in terms of an overall landscape concept. The need to visualise
and co-ordinate garden development, as well as the built structures, in terms of an
overall site order, was expressed. The purpose of the manual is, therefore, to provide
guidelines for the design, selection and siting of the landscape furniture, as part of an
overall theme for the garden.
Landscape
elements should not be seen on their own but as part of a larger theme or image for the
garden. "Imagability" is influenced by the language of forms and materials that
is used, together with detailing, colour and graphics. A "family" of landscape
elements is proposed to ensure that these are not only in keeping with the garden, but
with each other. If it is necessary, it should be possible to group the various elements,
with standard fixing details, which are easily maintained or replaced. The design of even
the smallest element, therefore, should be related to the overall theme.
Finally, the
hard landscape elements must not detract from the beauty of the setting or the primary
function of the botanical garden as a display of flora. The elements must therefore be
simple, unobtrusive and complementary to the botanical role and special qualities of this
internationally important place.
A survey was
made of all the existing landscape elements so as to identify existing themes, comment on
design appropriateness and identify potential themes. The guidelines in the manual cover
co-ordination, materials, siting and actual examples of elements. The elements have been
divided into categories which can be added to over time to accommodate additional items
The signage
study identified that Kirstenbosch Garden could be divided into the following functional
zones, each having a different character and different needs in terms of landscape
furniture: gateways, parking areas, restaurant area, garden area, forest walks and contour
path.
The
gateways, parking and restaurant areas tend to be more formal and hard in character,
carrying the greatest density of people and activity (information services, deliveries,
refuse collection, etc). The garden area is more informal and softer in character, with
the visitors being more dispersed, while the forest walks and fringes are more natural,
tapering (moving) into wild mountain fynbos and kloof forests, with fewer people.
These
differences in the character of the functional zones will require some variations in
paving and landscape furniture themes, within the larger concept.
Paving survey
Historical precedent
The original paths and service roads were constructed of reddish laterite
gravel, but most of these have been paved over time to reduce maintenance, although gravel
is still used on the upper forest routes. Paving materials currently in use include:
asphalt (main access and service roads); precast roadstones (service roads and paths);
brick (new footpaths); stone cobbles (old footpaths); gravel (forest paths); wood chips
(minor paths); and grass (low traffic areas).
Design comment
The asphalt roads are unsympathetic in the context of a botanical garden. They
are being replaced in certain areas, but have recently been laid at the new Research
Centre. Precast interlocking roadstones have an "engineered feel" - also
availability and consistent colour are a problem.
Brick of a
yellow ochre colour has been used on the new paths - adding yet another pathway material.
The natural clay bricks tend to weather better and tone into the landscape, as they
harmonise in colour with the sandstone edges and walls. The rectangular brick shape
provides a neater edge than the "zig-zag" shape of the roadstone.
The older
stone paths and steps, where small cobbles have been used in combination with flagstones
steps, are the most attractive of all the paved surfaces. New stone paving, as well as
repaired areas, have been laid with excessively wide cement joints and are not of the same
standard as the older work. The edges and junctions between the various materials are
generally unresolved and untidy.
The speed
humps on the approach road, with their bright yellow paint markings, might be suitable in
an urban connotation but are not appropriate in a botanical garden.
Paving guidelines
Paving can be used to express the hierarchy and function of paths and roads
within the garden - and be a unifying element. A limited range of paving materials and
colours should be used, in a consistent manner, to reinforce this hierarchy and unity.
Materials
The traditional sandstone cobble paving should be retained and this theme (once
the dominant paving theme), which includes the sandstone edges and channels, should be
extended where appropriate. Informal materials, such as gravel, wood chips and grass,
could be used for secluded or minor pedestrian routes, while more formal hard-wearing
materials, such as brick, could be used for major pedestrian routes.
All paths
constructed from interlocking roadstones should be lifted and the roadstones re-used for
parking areas. Asphalt/premix should be phased out entirely and speed humps and traffic
paint on paving avoided. Grass reinforced with gravel could be used for low traffic areas,
such as overflow parking.
Siting
Suggested paving for various functional areas and routes includes: main parking
areas/service roads - interlocking roadstones in ochre colour; major pedestrian
routes/precincts - yellow-ochre clay brick; minor pedestrian routes/seating areas
-sandstone cobbles; forest roads - laterite gravel; forest walks - wood chips; informal
routes - grass/stepping stones.
-----
Clean water for Modderspruit
A pre-paid
water meter system recently installed at Modderspruit provides the entire community with
clean potable drinking water, while eliminating the culture of non-payment for services
and simultaneously effecting significant water savings.
Following
installation, average water consumption dropped by 5 500kl/month or 66%, resulting in an
average monthly saving of R 7 865.00 on the total bulk water supply cost. Andre Greyling,
managing director of Consultburo (Pty) Ltd, consulting engineers for the Modderspruit
project (a wholly owned subsidiary of BKS (Pty) Ltd), attributes this to less wastage and
more efficient use of water.
"Residents
now use the potable water for domestic purposes only," says Greyling. "Other
water sources are used, for instance, to wash taxis and irrigate vegetables. Greater care
is also being taken to avoid leaving taps running."
A further
advantage is the computerised system which keeps an up-to-date database, allowing the
water authority to monitor user patterns, such as variations in water consumption for
different seasons and parts of Modderspruit. If there is a sudden decrease in consumption
in one area, for instance, the possibility of illegal connections can be investigated.
Modderspruit is located near Brits in the North West and has an estimated population of 10
000.
Between 1990
and 1995, an average annual population growth of 5% was recorded. This rapid
"urbanisation" in a rural area with limited existing infrastructure has resulted
in dire circumstances. Prior to the installation of the pre-paid system developed by
Consultburo, the total population was dependent on an erratic water supply of untreated
water from privately owned boreholes
In September
last year, Tryphinah Mbele of Modderspruit became the millionth recipient of potable water
in South Africa since the 1994 elections. A backlog of more than 10 million citizens with
no access to clean, affordable water still remains. However, the Department of Water
Affairs and Forestry (DWAF) has been striving since 1994 to bring at least 25 l/person/day
of fresh drinking water to within 200 m of every person in the country. Although far below
the standard level of service of 150 l/ person/day with water on tap in dwellings for
developed areas, it nevertheless provides basic access to hygienic water for all.
A crippling
factor throughout South Africa in the supply of clean water is the prevailing culture of
non-payment for services. For this reason Consultburo, in full liaison with the community,
proposed a pre-paid meter system. Neil Rodseth of Bambamanzi Trading, suppliers of the
pre-paid meters, explains that the equipment comprises an electronically-activated
solenoid valve, water meter, and microprocessor with input-output device. The system is
activated by means of a "smart card", which records a credit limit based on an
amount paid by the consumer in advance. The card is inserted into the meter to activate
water supply. Removal of the card results in closure of the solenoid valve, which controls
the release of water.
The
Modderspruit projects is based on the BOTT (build, operate, train, transfer) concept. The
system is designed for future upgrading to full reticulation - although the cost
implication of water supply to each dwelling would be high. Increased density of housing
units, while allowing optimisation of piping and associated savings, would be insufficient
to justify the expense at present, particularly since there would also be costs associated
with provision of additional storage facilities to cater for the increased consumption.
Funds were
provided for the project by the DWAF and Rand Water was responsible for its
implementation. Training in system operation was provided for the community and the local
authority (the Eastern District Council) which is responsible for the cost-recovery in
liaison with the Village Water Supply Officers. Units are currently purchased through the
Management Control System, which houses the central computer. Greyling believes it is the
responsibility of local government to operate and maintain such systems. "Design and
construction are the easy part of a water supply project. Effective operation and
maintenance are far more complicated and should be adequately budgeted for." This
often poses a problem, since many local authorities, while accepting the responsibility
for the development and installation process, are resistant to the ongoing aspect of
operation and maintenance. However, the long- term success of such projects depends upon
greater commitment in this respect."
Full
community participation and co-operation are the ingredients of Modderspruit's success. A
Labour Relations Officer from the community itself co-ordinated all labour related issues
during construction. Says Jan Greyling of GH Visser Construction:
"More
than 80% of the labourers were local residents, allowing maximum community participation
in the project. Thus the community itself has a vested interest in the system."
-----
A constructed wetland in a highveld
garden
John Masson
of Ecoscapes designed and built this residential wetland as an ecological system, along
sustainable lines, within the parameters of an indigenous garden which constitutes mainly
local species.
The wetland
needs a constant supply of water, so run-off from the roof is fed directly into the system
by means of an underground pipe. The planting comprises a good balance of emergent,
submerged and floating species, while the trees and shrubs surrounding the vlei are
riverine species. The water is stocked with indigenous vlei kurper - and insects, birds
and amphibians, related to marshy areas, have been attracted to the site. Masson believes
that a constructed wetland should have a sense of purpose in the garden landscape. An
impression should be created that the water is coming from somewhere and going somewhere,
so that it is not simply an isolated wetland but is relevant to the terrain. Hence the
simulation of a seasonal stream flowing into the vlei in which there is an area of open
water. The running water in the stream increases the visual interest and the size of the
feature, while providing further variety of habitat. During the winter months, the stream
features as a picturesque dry river bed with its locally sourcedpebbles and large pieces
of driftwood.
Seasonal
run-off from the roof and other hard surfaces of the house is pumped into the stream,
serving to top up the open water of the wetland, and since it runs over the pebbles, it
also oxygenates the water in the vlei. The stream runs whenever there is rain. Masson
emphasises that an ecological water feature of this nature must be designed around the
wildlife with which it will interact.
The wetland
is a small system and because the excavated area had fairly steep embankments, Masson was
obliged to line the pond with a 500 micron plastic liner, whereas his choice would
normally be a bentonite sealant on ponds or dams with slopes of 1:3. He comments that
bentonite is likely to last a lifetime, because if tree roots grow through the sealant, it
closes up around these and seals off potential leaks.
As a
precaution, there is a bed of river sand underneath the plastic liner, so that there is a
smooth surface in contact with the plastic and any sharp objects have been eliminated to
lessen the possibility of perforations that may result from the weight of the water.
Over the
plastic, there is a layer of soil - and to prevent the earth from washing away on the
steep slopes, before the plants have established sufficiently to act as stabilisers,
Masson has used sand bags (soil compacted into orange pockets) which not only create a
gentler slope but do not restrict plant growth. The soil depth on the periphery of the
pond is about half a meter which is adequate for reeds, bullrushes and sedges, whereas a
depth of 20 cm is sufficient on the bottom.
The island
(or mud spit) extending into the open water, to provide a breeding area for wetland birds,
was sealed along with the rest of the system but a layer of concrete was cast over the
plastic because a number of large rocks were positioned on the island. Soil was then
packed over the island. Masson maintains that it is a good idea to include a variety of
soils in the wetland. Black clayey soils provide an excellent habitat for a number of
aquatic life forms which serve as a rich food source for waders such as the Common
Sandpiper and Greenshank.
Once the
whole system was filled with water, emergent species such as the reeds, rushes and sedges
were planted on the banks. Masson comments that the wetland needs to be managed so that a
good water depth is maintained and this will prevent encroachment of the Phragmites and
Typha species into the open water. Sedges increase oxygen levels, create silt traps and
absorb excessive nutrients - besides creating an ideal habitat for insect life. Just above
the edge of the water, Panicum maximum, which is usually found in climax moist grassland
on the fringes of wetland, has been planted because it provides an abundance of seed for
seed eaters such as the Common and Orangebreasted Waxbills, Bronze Mannikins and
Blackthroated Canaries.
Submerged
plants, such as a Potamogeton species and a Lagarosiphon species - leafy, protein plants -
are utilised by the indigenous vlei kurper in the pond and help with oxygenation. Masson
observes that after the plant has established, there is a noticeable improvement in water
clarity - almost as though the plant attracts the sediment that is suspended in the water.
Nymphaea and
Nymphoides are the floating species and Masson mentions that, when these are planted,
their roots should be weighted down so that they are able to anchor themselves firmly in
the soil. They create shade in the area of open water and refuge for the fish and
amphibian life.
Riverine
species such as Combretum erythrophyllum and Celtis africana are planted on the banks,
along with Leucosidea sericea and Buddleja (a useful riverine pioneer), and Diospyros
lycioides for the fruit eating birds. The septic tank of this small holding, which is not
on the main sewerage system, is positioned near the wetland so that the trees will benefit
from the seepage. Masson points out that plant material within the French drain of a
septic tank aids the water purification process.
In the
backwater behind the island, there is an appropriate nursery for the young of the vlei
kurper. Masson has also made use of pieces of brush packed into the water as a refuge for
fish, as well as rocks and big logs. These logs also provide convenient perches for the
Cormorants that come in search of the fish. Other wetland species that have been spotted
on the site are the piscivorous Grey Heron, the Black Duck that is able to land in a
fairly small, confined area of open water - while Yellowbilled Duck have been seen feeding
off the Potamogeton and Greenbacked Heron searching out the fingerlings and tadpoles.
Recycling water
On this Kyalami property, use is also made of the grey water which is captured
from the bathrooms in the house and put through a simple filtration system, called the
Garden Rhapsody Water Re-using System, for irrigation of the bigger riverine trees in the
vicinity of the wetland that need additional water. The water runs through this
"re-using system", which removes soap and grease, into a tank and is pumped out
into the garden, immediately, so that there can be no bacterial build-up. This system is
positioned underground so that it is out of sight and it requires minimal maintenance -
just the cleaning of a very simple filter.
The inventor
of the series of Water Rhapsody Systems for water conservation, Jeremy Taylor, has been
chosen as a finalist for this year's Green Trust Environment Awards. He has developed a
number of water saving mechanisms for home owners, including the Poolside Tank which
allows purified backwash water to be re-used; a system of recycling grey water to flush
toilets; and the Rain Runner which collects rainwater from roofs, filters it and stores
it.
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Rehabilitation a Wetland - Lenjane
Vryheid
Carol Knoll
accompanied David Lindley of the Rennies Wetlands Project to Vryheid in KwaZulu-Natal
where the Lenjane wetland, an important hydrological system in the Mfolosi catchment, is
being rehabilitated by Mondi Forests, with input from Lindley and Stoffel de Jager of
KwaZulu-Natal Nature Conservation Service. According to past research done by Dr George
Begg, the wetland has been reduced from 1 200 ha to 700 ha by agricultural and forestry
activities. A number of factors about wetlands came to the fore during the excursion
through Lenjane.
The
boundaries of a wetland are not always that obvious to the untrained eye and it is
therefore difficult to determine whether a particular activity, such as a farmer planting
crops, is taking place within the boundaries of a wetland or not and whether it is having
a significant impact on the wetland. David Lindley pointed out that the parameters of a
wetland can be defined according to the colour of the soils, the density of mottles found
in a soil sample and the kinds of plants that are present. A wetland is an area where the
top 50 cm of the soil is saturated for long enough to be unfavourable to most plants but
favourable to hydrophytic plants, such as sedges, which are adapted to anaerobic soil
conditions.
There are
three sections to a wetland: the inner area which is permanently waterlogged and which
supports reed growth; the seasonally saturated portion in which sedges grow; and the outer
area which is temporarily waterlogged in which vlei grasses are in evidence. The term
"water regime"is used to describe how the wetness of the soil changes over time,
and the water regime has an effect on the colour patterns of the soils. Under anaerobic
conditions iron oxides are broken down and leached out so that the soil loses its
red-brown colour, turning a dull grey. Wetland soils are often referred to as hydric soils
and are generally grey in colour.
Temporarily
and seasonally wet soils alternate between being anaerobic and being aerobic. When
anaerobic soil dries out, iron oxides form in patches, often around plant roots, resulting
in orangey-red mottles. Grey soil which has many mottles is indicative of a zone with a
fluctuating water table. Permanently waterlogged soil is grey with almost no mottles. When
a wetland is drained, as with large areas of Lenjane, and the water regime is changed, the
soils retain their characteristic mottles, helping concerned parties to map out the
original extent of the wetland, so that it can be returned to its original status. As
Lindley expressed it: "Soils give you the history of the wetland, whereas plants
define the current extent of the wetland."
De Jager,
who had been on a number of Begg's wetland surveys and knew the value of Lenjane,
organised a survey to establish the exact extent of the portion of wetland which fell on
Mondi's land. This was mapped out by means of seven or eight days of soil auguring, done
by a group, made up largely of new agricultural extension officers, organised by Lindley
and De Jager. The soil samples taken with the augurs were tested for colour together with
this characteristic mottling and once this had been established and documented, a
management plan for the area was drawn up. The moment Mondi gave permission for the
rehabilitation to go ahead and the money was made available, forester Gary Pearson
commenced filling in drains with a backactor.
Plugging the
drains, made when the land was under agricultural use, was given priority because the
changes that these had caused to the flow pattern within the wetland had reduced the
wetness of the area, and the disturbance of the soil had made the area more susceptible to
erosion. Gabions will be put in at a later stage to encourage the water to spread out
across a greater area. Plantation trees and other exotic invaders, such as poplars and
bugweed, were eradicated from the demarcated wetland areas and the stream banks. Where
existing roads cut across the wetland, concentrating the water in one area, Pearson has
laid culverts underneath these roads to encourage water dispersal. In many degraded areas,
there are clear signs, after one full rainy season, of the return of wetland conditions in
the form of saturated soils and the new growth of sedges and other hydrophytic plants. The
management plan for the wetland includes management for grazing according to carrying
capacity and a detailed fire regime. Farm tenants have seen their grazing improve over the
last year as the water has spread out over a larger area.
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Restoring the Wakkerstroom Wetland
Herbicides,
applied to control excessive reed (Phragmites australis) growth, have helped to restore
the ecological system at the Wakkerstroom wetland with plants that were previously
suppressed due to the fact that such competitors were thriving.
The
Wakkerstroom Wildlife Heritage Trust site is one of the most extensive wetlands in the
highveld grasslands, which have been so severely degraded by man's activities. The
wetland, used by several species of birds which are rarely found elsewhere, is the heart
of an extensive potential conservation area.
However,
certain severe ecological problems were being caused by an excessive growth of Phragmites
australis, a naturally occurring plant species but one which displays aggressive
characteristics if conditions favour it. Such conditions existed at Wakkerstroom.
Because of
the construction of a dam upstream of the town, the natural scouring effect of floods had
been minimised. This, exacerbated by a sewage treatment plant which was discharging
enriched water, created an ideal situation for the development of a reedbed. The bed
became more and more extensive each year and eventually it was so vast and competed so
effectively with the other plant species that it was, to all intents and purposes, a
monoculture, totally lacking in the species diversity so necessary in a nature reserve.
Furthermore,
reeds in a highveld winter are tall, well-aerated and tinder-dry. A fire in a reedbed is a
fearsome thing and under the influence of westerly winds, the town had been in danger on
several occasions. Clearly, a solution had to be found. Enviro Weed Control Systems had
carried out reed control tests on the Blesbokspruit, which were monitored by scientists
from the Gauteng Department of Nature Conservation. Careful assessments over a period of
time showed that these treatments had not caused an imbalance nor adverse effects on
aquatic species such as crabs, frogs, waterfleas, birds and the like. On the basis of
these results, the company was approached for an ecological evaluation of the Wakkerstroom
situation. A report was drawn up and accepted in principle.
Funding was
obtained and a decision made to treat some 20 ha in the form of a rough "T" with
the cross bar along the shoreline adjacent to the town, thus providing the fire protection
where it was most required. The leg of the "T"pointed westward across the
wetland, so as to divide the reedbed, further reducing the fire hazard. A remarkable
feature of this decision was that a portion of the treated area fell virtually within the
boundaries of the town of Wakkerstroom. Not only was innovative technology necessary but
also the utmost care had to be taken with every detail and indeed lots of good
old-fashioned common sense came to the fore.
The already
well-proven combination of a suitable microlight aircraft with a skilled pilot, correctly
set Micronair droplet generators, the correct dosage of the two selected herbicides -
Tumbleweed and Arsenal at a 6:3 ratio - and patient waiting for the correct weather
conditions, all came together in January 1997. Work commenced at first light when
atmospheric conditions were the most stable. In the situation at Wakkerstroom a
"quick fix" would have been disastrous. Any dramatic, change in habitat would
have had a negative effect on the whole ecosystem. Instead of this, the herbicide system,
including the choice of chemicals and the balance of dosages, proved to be exactly
correct. A gradual but definite change commenced shortly after the treatment, in that the
growth of the reeds in the treated area was stopped. With their vigour reduced and the
gradual opening of the canopy so that more light could penetrate to lower levels, many
subtle changes took place. Dormant seeds were able to germinate and grow. Plants which
were present in the area, but suppressed due to competition, began to re-assert themselves
in the ecosystem. The changes enabled various insects, amphibians and small animals to
return and bird species were no longer limited to the reedcover. The full effect was
realised in the next summer season.
Less open
water resulted from this single treatment than was perhaps originally expected. A casual
look at the area could lead to the conclusion that the fire hazard has not been
sufficiently reduced. Quite the contrary is true. With the removal of the reeds in the
treated area, the fire risk is now greatly reduced, while still allowing more gentle
fires, which are part of the ecology of the highveld grasslands, to burn. Patches of open
water can be created by further treatments in selected areas in the future. Areas of
deeper water will be chosen so as to enlist the help of natural conditions in the
long-term maintenance.
In the
future, management will have to continue. A nature reserve is by definition an
"island" and pressures from the other side of the fence create unnatural
effects. Water enrichment, reduction in total stream flows, increased (or decreased)
seasonality of stream flows, increased numbers of birds due to the attractive habitat and
many other factors will all impact on the vlei and its inhabitants. Even the needs of
visitors will need to be borne in mind. Nature cannot be allowed to "take its
course" - that course has already been too drastically altered. It will be necessary
to reduce the total quantity of reeds further in order to reduce the evaporation of the
available water. Each reed plant acts as a highly-efficient pump and a balance will need
to be established in the long term.
As already
discussed, careful consideration will need to be given to the establishment of areas of
open water. For several reasons, the application of herbicides should be to vegetation,
not to open water - so this is a further challenge to the ingenuity of those responsible. |
