Contents
of December 1999
EDITORIAL
NEWS
LETTERS
BOOK REVIEW
TREE OF THE ISSUE
Heteropyxis Natalensis
GREEN BUILDINGS
Megawatt Park
FEATURES
1999 ILASA AWARDS
Stormwater Harvesting
Reviewing the latest billboards
Re-introduction of
indigenous grasses on a golf course
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EDITORIAL
The end of
the year is at hand and The Urban Green File wishes its readers a prosperous 2000. We
extend heartfelt thanks to our advertisers for their meaningful support during 1999. We
are delighted to report a 50% increase in subscriptions over the year and we thank all our
subscribers for their support. And our website gets on average 3 000 hits a month!
We have an
exciting project for next year, which we will elaborate on in some detail in the Jan/Feb
2000 issue, and that is The Urban Green File's Environmental Stewardship Awards which will
give recognition to golf clubs and golf course managers who are taking care of the natural
environment. This awards programme has the support of the National Turfgrass Association.
The word
'steward' means a person entrusted with the management of property which does not belong
to him - it belongs to future generations. Many golf course managers in South Africa, with
support from their clubs, are opting for environmentally responsible approaches on their
courses. Awards will be given to those who are making a serious attempt to conserve water,
to manage water and soil quality, to conserve and create wildlife habitat, to implement
integrated pest management, to eradicate invasive plant species and to minimise waste.
Progress towards environmental improvement is what will interest the judges.
In this
issue, we have not specified an 'Insult' and an 'Inspiration' but in our review of the
latest billboards (page 13) there is one project which shows that thought has been given
to the surrounding urban environment, another in which a vague, not very successful,
attempt has been made to do this, while a third is inappropriate and a fourth serves as
the perfect example of visual pollution at its worst. The South African Manual for Outdoor
Advertising Control has won an ILASA Award (page 20), so we thought it appropriate to
attempt to stimulate some discussion on the subject of outdoor advertising. Please send us
your comments, in the form of letters to the editor, on the billboards that we have
reviewed or on others that you feel need to be brought to our attention - anywhere in the
country.
We have two
competitions running in this issue. Briza Publications is giving away copies of the
fabulous new 'Guide to the Acacias of South Africa' and Osram is giving away energy
efficient compact fluorescent lamps (see page 42).
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NEWS
Architectural design competition for Pretoria Municipal Headquarters
The winner
of the socalled 'Project Phoenix' competition was Holm Jordaan and Partners. According to
the design team, it was the partnership's expertise in recycling buildings and in urban
design, and its environmental consciousness, which they have over the years integrated
into 'eco-architecture', that proved to be the answer. The end result is not just a
functional building but a new South African place that fits into the urban fabric, making
the best of pedestrian and traffic routes and celebrating views towards and from the Union
Buildings and CBD. According to the architects, the building needs to fulfil its civic
duties giving people freedon to interact with the urban environment and creating an
identity people will be proud of. It needs to be a place that feels like South Africa and,
therefore, the building/site looks like part of a flat Highveld plain with a monumental
outcrop of boulders that divides the plane into squares and atria where trees grow and
people move freely in shelter and shade.
Large water
tanks on stands double up as lampposts and banner stands, some of them on or around the
square defining spaces, others situated in atria to stabilise interior temperatures. The
stored rainwater will be used for gardening or washing down of the paved surfaces. The
building systems of utilising natural light, energy and other resources are very
sophisticated and in line with the latest research in these fields. The technology is
appropriate to Pretoria's climate - and this will be a healthy building right from the
beginning.
Traditional Plant
Use Garden at Pretoria Botanical Garden
The mission
of the Pretoria National Botanical Garden is to help South Africans to get to know and to
understand their rich plant heritage. Traditional healing is an important part of southern
Africa's social and cultural heritage. The new Traditional Plant Use Garden is an
ethnobotanical centre with a specific Ndeble theme - it comprises a living display of
traditional medicinal plants used by the Ndebele and three traditional Ndebele huts.
Displays of beadwork and the arts and crafts of the Ndebele, along with posters describing
the uses of various medicinal and edible plants and specimens of parts of these plants,
will be exhibited at the centre.
The centre
will strive to create awareness of plants that are under threat from the muthi trade,
which will contribute to conservation efforts. Gardens such as these keep plants in
existence that might be destroyed in the natural environment and raise awareness of plants
on the Red Data List. It is envisaged that the centre may become a venue where traditional
healers can meet to exchange knowledge, and provide an interactive focus for medicinal
research, bringing traditional healers and medical and other students together.
1999 Eduplant
winners lead the way to food security
Minister
Ronnie Kasrils presented the winners of the highly successful EduPlant schools'
permaculture competition with a range of prizes, at a function at Nest Phuting School in
Gauteng, in October this year. Maiketso Primary School in the North West Province was
chosen as the National Advanced Winner of EduPlant 1999 from 64 finalists. Constantia
Primary from the Western Cape was awarded second prize in the Advanced Category and Enyosi
Primary from KwaZulu-Natal, third prize. In the Emerging Category, Monakato Primary from
the North West Province were the winners, while Loti Primary from Mpumalanga and Ntolo
High forn the Northern Province came second and third, respectively.
The 64
finalist schools selected from over 300 entrants were invited to spend four days together
at Nest Phuting School to present their projects for adjudication, attend environmental
workshops, go on nature trails and, generally, share their experience and pool their
diverse indigenous cultures in a creative and highly entertaining 'eco-talent show'. One
of the workshops run by Eco-Access demonstrated how the environment can be made more
accessible to disabled people and another run by Rutec discussed entrepreneurial skills.
Each finalist school was presented with a package of resources including environmental
posters, books, seeds and R500 in cash. The provincial winners were given gardening tools
and the national winners cash prizes for the further development of their projects.
EduPlant has
been funded by Eskom's Corporate Social Investment Division for the past five years and
has this year been joined by DWAF who contributed substantially to EduPlant 1999. Trees
for Africa initiated the prject in 1994 with the aim of encouraging the greening of
schools and environmental awareness. Many impoverished and severely disadvantaged schools
that had never heard of permaculture nor thought of planting trees and vegetables are now
independent of feeding schemes as a result of EduPlant. This year, EduPlant organised 27
workshops, three in each province, to introduce permaculture to educators - over 1 500
teachers attended these workshops and learnt how to incorporate permaculture projects into
Outcomes Based Education.
The design
of a garden that incorporates water harvesting, conservation and management, soil
enrichment and conservation, the planting of a diverse range of food and indigenous
plants, energy management, livestock integration and cultural knowledge, facilitates the
teaching of virtually all school subjects.
Threatened flora
sites in Cape Metro Area
A study by
the Botanical Society of South Africa has revealed that some of the rarest plant species
in the world are found in pockets of veld in low-lying , built-up areas of the Cape Flats.
The study includes the entire lowlands area of the Cape Metropolitan Area (CMA) and some
118 areas of strandveld, sand plain fynbos and renosterveld vegetation. The aim of the
study is to identify a minimum set of areas that will ensure the preservation of the
unique plants of the Cape Flats, if conserved collectively.
A total of
37 areas have now been identified as core conservation areas - seven of which already have
secure conservation status. Only four of these are, however, managed effectively. It has
been recommended that all the core conservation areas be given official conservation
status and be managed appropriately - an interesting challenge for local authourities and
other decision makers in the CMA.
Gauteng Institute
of Architecture Biennial Awards of Merit
There were
21 submissions for evaluation this year and each was visited by the panel of assessors
comprising: Ozi Nkabinde, Michael Scholes, Luis Ferreira da Silva, Iain Louw and Jo
Ratcliff. Awards were given to the following three buildings: Munich Reinsurance Centre on
Empire Road, Johannesburg - designed by Stauch Vorster MOM Architects; House Lategan in
Westcliff, Johannesburg - designed by Slee & Co; and AECI at Parklands Estate -
designed by RFB Consulting Architects.
The
corporate headquarters for the Munich Reinsurance Centre (see article 'Embodying the
Principles of a Green Building' in February '99 issue of The Urban Green File.) was
commended by the assessors for its "concern for environmental control", along
with its "modernist design approach", its "restrained use of
materials" and the so called "'socialisation' of the plan".
Siyaphambili
upgrades Portnet's worker facilities
Siyaphambili
is the name given to a R65-million project to upgrade Portnet's worker facilities in six
SA ports. The name means 'we are moving forward'. The facilities comprise change rooms,
locker rooms, ablutions, mess rooms and recreation areas. They are generally located on
the periphery of harsh industrial working environments, such as quaysides, cargo handling
areas and dockyards, sited adjacent to high traffic areas, subject to harsh weather and
pollution and screened from public view.
Siyaphambili
is attempting to reintegrate these facilities into the port environment - to create safe
areas for recreation, to make buildings bright and welcoming and to open up views of the
waterfront. Design guidelines were developed through consultation to identify specific
user requirements and careful design responses. A team of young professionals was
appointed by Protekon to co-ordinate the project on a national and regional level.
Workshops were held in each port where architects met with the facility users to analyse
needs and prepare drawings describing the work to be done to ensure the approval of
workers and management. The execution of the work was done through an empowerment
maximisation programme comprising previously disadvantaged project teams and outsourcing
construction work to black owned SMMEs.
One of the
best examples of this design response can be seen in the upgraded Shed 12 workers'
facility in the Port of Durban. Here the use of expressive colours, murals and mosaics and
a dynamic roofscape create a beacon in the harsh monochromatic surroundings. The murals
integrate with the architecture to form a fully functional artwork rooted in the local
context - with one of the murals depicting Samson who has worked at the port since 1962.
Planning and
management of a nominated World Heritage Site
At an
afternoon visit to Sterkfontein Caves, organised by the Vaal Branch of the SA chapter of
the International Association of Impact Assessment (IAIAsa), Melinda Swift of the Gauteng
Department of Agriculture, Conservation and Environment (DACE) gave a presentation on the
planning and management of the nominated World Heritage Site officially known as the
Fossil Hominid Sites of Sterkfontein, Swartkrans, Kromdraai and Environs.
South Africa
signed the World Heritage Convention in 1997. The Convention strives to "protect
natural and cultural properties of outstanding universal value against the threat of
damage in a rapidly developing world". The nomination for World Heritage Listing of
the 'Sterkfontein' site which has been named the 'Cradle of Mankind' was submitted to the
World Heritage Committee in June 1998. The site comprises a unique band of
palaeo-anthropological sites, with the most prolific findings worldwide of the remains of
hominids from 3, 3 million years ago and fossils of the plants and animals that were found
in the area at that time. Mrs Ples, the first complete Australopithecus skull, was found
in the Sterkfontein Caves in 1947, while in 1994, Little Foot, a set of 3, 5 million year
old hominid foot bones was found in these caves. In 1998, the entire skeleton was located.
Although the category in which the site has been nominated is 'Culture', because the site
is a testimony to significant stages in human prehistory and to the development of
cultural traditions, unique, unspoilt Bakenveld grasslands with their ecological
characteristics add value to the nomination.
In January
1999, UNESCO sent representatives to assess the nominated site and to evaluate its
protection and management. The World Heritage Bureau considered the evaluation report and
recommended the site for listing in July 1999. The World Heritage Committee meets in
Morrocco in December this year to ratify the recommendations of the Bureau and to announce
the new list of World Heritage Sites. The nomination is judged in terms of the scientific
uniqueness of the site and the commitment and plans to conserve the site.
Gauteng's
DACE is responsible for the planning and Swift said: "The area is 47 000 ha in terms
of cultural significance and the crux of the nomination is that one cannot separate the
cultural from the environmental issues, so the whole area has to be protected - air
pollution, for example, destroys fossils. Everything had to be subservient to
environmental issues. The site includes about 700 privately owned landholdings and falls
across seven local authorities. The public participation process is an on-going, huge
challenge - just to reach everybody has been difficult and there are land tenure issues in
the area - and we had to deal with misinformation.
"Most
of the people are located along the south western edge, while the central part is an
almost unspoilt area of magnificent grasslands, bushveld and kloofs with leopards and
brown hyenas and red data floral species. This has been demarcated as a low use intensity
zone, along with wetland areas and high ridges. Tourist nodes will be developed in high or
medium intensity use zones. A huge interpretation centre is one of the many developments
proposed for the area, while mass tourism will need to be kept off the dolomites where
Wits University is continuing with its digging. We are thinking along the lines of
different grades of tourists. The success of the project lies with a balance between
restrictions and incentives. "
Controversial
proposed casino development
The proposed
casino on Swartkop, which has been the subject of a heated controversy, falls within the
area nominated for World Heritage Listing. Initially, Gauteng's Gambling and Betting Board
granted a licence to this development and the Gauteng cabinet concurred with the
recommendation. Later, the cabinet reconsidered and decided not to concur with the
granting of the licence and the licence was withdrawn. The developers appealed and the
decision was made that Gauteng was no longer the appropriate authority to evaluate the
application but that the National Department of Environment and Tourism (DEAT) was
responsible because of the possible World Heritage status of the site.
Wynand
Fourie of the DEAT commented: "We said that, because of the management requirements
of a World Heritage Site, a casino was not a compatible land use in the area. Gauteng has
compiled a land use plan which recommends low use intensity in the area of the proposed
casino at Swartkop. Recently, however, because of protest marches and a local petition in
favour of the casino, we have sought expert legal opinion on what we should do. The
problem is complex and needs to be handled fairly."
In the
September issue of 'Maropo (the bones) Speak', the Newsletter from the Cradle of
Humankind, Mary Metcalfe, Gauteng MEC for DACE, said: Our mission is to work with all the
stakeholders in the region to achieve an acceptable balance in the area of the nominated
World Heritage Site between the conservation of cultural and natural resources and the
economic development activities of the area."
Cities State of
the Environment Reports
Cape Town,
Durban, Johannesburg and Pretoria are participating in the Cities Environment Report on
the Internet project, which is an international endeavour based on the Local Agenda 21
concept. The project's aim is to facilitate access to environmental information for
decision making and the raising of general awareness in cities to support sustainable
development. These four SA metropolitan areas have joined the 27 cities, worldwide, that
have State of the Environment Reports on the Internet.
Science goes
shopping in nature's drugstore
A nationwide
bioprospecting project has been launched by the CSIR's Chemical and Microbial Products
Programme. The aim is to discover, develop and commercialise novel biological products,
such as pharmaceuticals and natural pesticides, from SA's 23 000 species of indigenous
plants and thousands of micro-organisms. In the next ten years, over 250 000 extracts from
these sources will be screened for commercially important biological substances. The
project has already yielded a novel appetite suppressant, a high intensity sweetener and a
mosquito repellent.
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LETTERS
Not quite there...as a model for green housing
Response
to the article by Gerald Garner on the All Africa Games Village in the Green Products
& Services supplement to The Urban Green File July/Aug 1999.
I am deeply
concerned that this village is presented as a model of ecological development. Is everyone
involved in this entire 'green' process completely unaware of the benefits of plants? Are
2000 donated trees the best they could do in a multi-million rand urban development? This
village is situated next to one of South Africa's busiest highways. Where are the
windbreaks? Where are the parks? Will they rehabilitate the wetland?
What good is
a 300mm roof overhang - is this something different from standard building practice? I am
not convinced that one coat of plaster paint is a significant insulator. Tremendous energy
and cash savings are achieved by regulating the micro-climate around the house with
plants. The use of deciduous trees and trellices with creepers can reduce heat in the
summer, while still allowing the winter sun to penetrate. Windbreaks of shrubs and trees
can deflect hot and cold winds, channel cool breezes and create winter sun traps. These
measures also extend the lifespan of buildings by protecting them against solar and wind
degradation. Appropriate species selection can meet many human needs - food, medicine,
leaf mass for garden compost and economic resources for small industries.
The addition
of solar water heaters and geyser insulation removes a major energy and financial cost
within a short time. A community solar battery recharging station could provide
employment, while removing dependency on ecologically destructive and fossil fuel
electricity sources.
Why do South
African property developers and environmental consultants so steadfastly ignore the
harvesting of rainwater from roof surfaces? Rainwater tanks should be obligatory. To
complicate matters even further, asbestos roofs have been used, which makes all water
harvested at the Village unfit for drinking. It could still be used for the toilets,
though. The water from hand basins could be directed to toilet cisterns and other grey
water could be directed into the garden. There are no gutters or lawn, and soil erosion
should follow soon!
In SA
developments, there is a conspicuous absence of landscaping designed to harvest, store and
productively utilise water. Swales, ponds and reservoirs can deliver an effective water
management strategy that could provide for space intensive urban agriculture, urban
greening and support home industries.
Trees for
Africa have also expressed concern that the 2000 donated trees are not being looked after.
These trees will moderate temperature, supplement moisture, reduce dust and glare, reduce
stress and clean the air from the surrounding motorways and industries!
Dominique de Bruin, permaculture consultant
The All Africa
Games Village, East Bank Alexandra
Another response to the article in the Green
Products & Services supplement.
Have we really come to this? That we market indictments as achievements. In a village
"where people will want to live"! Who? The writer of this article?
If you want
a roof overhang to protect a building, then you must make sure that it does. Exposed water
pipes on the walls may heat the room in winter, but they will also do so in summer. The
short length of water pipes should not be hailed as an environmental achievement when it
is merely a way of saving on building costs. Before we had no ceilings in low cost housing
units, now we have ceilings - but this is not a great achievement. It is dangerous to
praise minimal improvements. We must aim higher. The colour on the roofs won't last and,
in any case, the natural grey of Everite is the best colour to reflect light.
The Village
is being hailed as an ecological achievement - and it should not be. Our standard low cost
houses (51/9) have always been of bad quality and these are not much better. This is a lie
being sold on environmental principles. A piece of insincerity which shows environmental
concerns in a bad light and puts environmental planning into disrepute!
Hans Wilreker, architect and urban designer
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BOOK REVIEW
Guide to the Acacias of South Africa
Author:
Nico Smit
Photographs: Nico Smit
Publisher: Briza Publications
Another of
Briza's in-depth, field guides with its clear, detailed photographs, Guide to the Acacias
of South Africa by Nico Smit, has been published recently. This is so much more than a
field guide - the book attempts to give a complete account of all 40 recognised species,
subspecies and varieties of the genus Acacia that occur within the borders of South
Africa. Four pages are devoted to each form and these include numerous, extra-sharp,
close-up, colour photographs of every aspect of the tree, a distribution map, a chart of
the phenology of the species and a comprehensive text.
'Tree
spotters' now have every chance of identifying our Acacia species and of discovering many
interesting facts about the third largest woody plant family in South Africa, the
Mimosaceae - such as the fact that these leguminous species enrich the soil under their
canopies, contribute to the problem of bush encroachment in overgrazed grassland and have
traditionally been used as food and medicine for humans. The flowers of several Acacia
species are important sources of nectar for bees and the production of honey.
The
inclusion of the simple, chronological charts, giving the phenology (the seasonal pattern
of leaf emergence and leaf fall, flowering and fruit-bearing) of each species, is of great
merit and deserves commendation. The authority citations, naming those who originally
described the species, is another first time inclusion in a botanical field guide. The
location of the 'type' specimen, the material from which the plant was first described
which is now housed in a herbarium, is also cited. The habitat of each species is
described in detail: A. xathophloea, for example, is found in low-lying areas in
association with water. Grows in swampy areas and along margins of lakes, pans and river
banks. It often forms dominant stands in seasonally flooded areas on alluvial soils.
There is a
key at the back of the book, which is not complicated with too much technical detail. The
key is primarily based on vegetative plant characteristics - growth form, thorns, shoots,
bark and leaves, because reproductive plant characteristics are only present for a limited
period of time.The second last page of the book is demarcated in millimetres, so that the
sizes of leaves, flower heads and seeds can be compared with those given in the book.
Another splendid field guide from Briza!
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TREE OF THE ISSUE
Heteropyxis Natalensis
Commonly
called the Lavender Tree
Landscape
designer and contractor Jeremy Stubbs of Stubbs Landscapes has chosen Heteropyxis
natalensis as Tree of the Issue. "I have based my selection on the tree's
versatility. It can be used in the small garden, larger landscape and in environmental
rehabilitation," said Stubbs.
It is a
small, slender, dainty, upright, neat tree with drooping foliage. The shiny, green to dark
green leaves give off a distinct lavender scent when crushed. It is semi-deciduous and
produces attractive autumn colours ranging from dark red to purple when it is planted in
full sun. The masses of small, cream to yellow coloured, fragrant flowers attract a
multiplicity of insects, including butterflies, which in turn attract insect-eating birds.
The tree's pale grey bark flakes off to expose decorative pale orange to white patches
underneath. The bark is creamy-white on younger trees. The natural habitat of Heteropyxis
natalensis is on rocky hillsides, in wooded grassland and along forest margins.
Stubbs has
used the Lavender Tree, which is indigenous to the KwaZulu-Natal coast, in his
rehabilitation project at Princes Grant Estate on the North Coast. He used it on the
margins of patches of rehabilitated coastal forest and on the interface between the
natural bush and the golf course. It has also been used as a screening tree in clusters in
the gardens of the houses on the Estate and makes an ideal specimen tree in the courtyards
because of its small size and neat shape. Stubbs' landscape design concept at Princes
Grant encourages the home owners to use species that occur naturally in the area, in their
gardens. In KwaZulu-Natal, Heteropyxis natalensis grows at a reasonable rate of about 1m a
year.
Stubbs has
also used the tree in gardens in Johannesburg, as a specimen tree in smaller gardens and
in groups in the larger landscape. Because of its compact, neat appearance, it is an
appropriate tree for formal gardens. He says that it does well on the Highveld and, in
fact, seems able to adapt to a wide variety of conditions. He has found that it can take
moderate frost, but doubts that a juvenile tree would survive severe frost and it needs to
be protected for the first year. Aside from that, the tree does not need any special care.
Stubbs has had more success with small trees - 20 or, at the most, 50 litre trees - than
he has with transplanting bigger trees, as the smaller trees grow faster and usually form
a better shape. The Lavender Tree is readily available from nurseries in both
multi-stemmed and single-stemmed forms.
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GREEN BUILDINGS
Megawatt Park
Factors such
as inefficient energy use and poor indoor air quality cost South African businesses
millions of rands each year. The Green Buildings for Africa programme, initiated and
managed by CSIR Building and Construction Technology (Boutek), seeks to establish
incentives that will encourage greater awareness of the environment in buildings. The
programme assists property owners in realising higher returns on their investments,
reducing operating expenditures, increasing property value and improving portfolio
performance, while it has a positive impact on the comfort of tenants and contributes to
the protection of the environment.
Megawatt
Park, Eskom's head office in Sunninghill, Gauteng, signed on to the Green Buildings for
Africa programme in 1998 and was assessed by means of interviews and a site visit in May
1999, according to the criteria of the Building Environmental Assessment and Rating System
(BEARS), developed by Boutek. The main objectives of the environmental assessment are: to
provide market recognition for buildings where the environmental impact has been reduced;
to encourage the best practices in designing, retrofitting, operating and maintaining
buildings; to set criteria and standards beyond those required by law and regulations; and
to raise the awareness of property owners, facilities managers, designers and occupants
about the adverse impacts of buildings on the environment.
The
assessment process on Megawatt Park was done in two parts and credits were awarded where
specified criteria were met. The first part assessed the building and its services and the
second part assessed the operation and management of the building - according to global
issues and the use of resources, local issues and indoor issues. Megawatt Park received an
overall classification of 'excellent', based on 89 and 85 percentage points, respectively
- and, although there is still room for improvement as the recommendations in the report
indicated, the assessment showed that the standards of operation and maintenance are very
high.
Carol Knoll
interviewed Billy Smith, maintenance manager of Megawatt Park, to establish the measures
that have been carried out to earn the building the highest classification.
Water
conservation measures involve economy drives on urinals in 108 men's toilets. The tipping
time of the tip trough urinals has been reduced by a quarter through the addition of ice
to the troughs. This procedure reduces odours and the continuous, slow melting of the ice
acts as a flushing mechanism. The procedure is still at experimental stage and there are
no figures available, as yet, to establish the exact water savings. Over the last two
years, in an on-going programme, flow regulators have been fitted into the spouts of 80%
of the taps in the building and to all the showers. As Smith comments: "This measure
throttles back the water flow to 2,5L/min and yet there have been no complaints from
employees. All the toilets in this vast building have been set on the lowest flush time of
7, 5L and again there have been no complaints."
Another
water conservation measure is the collection of stormwater in two dams on the property for
landscape irrigation purposes. "The only problem here" says Smith "is that
in a low rainfall season there is not enough runoff and we have to supplement with
municipal water. In a good year, if one dam catches an excess of water, this is pumped to
the other to avoid waste through overflow." The extensive indoor atria gardens, that
Megawatt Park is renowned for, are not highly water consumptive because they are grown in
hydroponics.
Waste
management involves the shredding and baling of all waste paper and cardboard on the
premises. This is sold for recycling and Megawatt Park makes between R12 000 and R 13 000
a month. There is a large motor repair shop on the premises for the fleet of vehicles and
all the oil from oil changes is discarded into an oil pit . This is sucked out and
collected on a monthly basis by an oil recycling company. All turps and other thinners
utilised in the paintshop on the premises are disposed of in a separate bin.
For a number
of years now, all fluorescent tubes have been disposed of in 'Tubie' bins - a product made
solely for this purpose. The glass is crushed in the air-tight bin by the simple winding
of a handle and taken away by Tubie when the bin is full. Smith says: "This system is
100% efficient, before we had to dump these tubes into a disposal bin with everything else
and the glass shattered and the gas escaped into the atmosphere." All biodegradables
from the kitchen are collected separately and handled by a commercial waste company and
grease traps in the kitchens mean that the wastewater is grease free. Old carpeting from
the building is given to staff members and old screens, furniture and computers are
donated to schools.
Environmentally
sound cleaning procedures
Megawatt
Park houses over 4 000 employees and R 7 million a year is spent on the cleaning of the
building. Most of the cleaning is outsourced and the contractors have to use approved
cleaning fluids. Fumigation, as a pest control procedure, is done every three months and
again the levels of toxicity need to be declared and approved. The requirement to use
environmentally sound materials and procedures is built into the contracts of all the
contractors that Megawatt Park utilises.
Energy
efficiency was Smith's primary function when he first joined Eskom in 1985. A Building
Automation Computer controls and monitors the utilisation of energy in the building. The
temperature and humidity on every floor is being recorded by the computer, every minute of
the day, and every chiller and boiler is monitored. If any piece of equipment exceeds
demand, it is shut off.
Smith says
that since joining the Green Buildings for Africa programme, Megawatt Park is looking at
negotiating new electricity tariffs with Eskom, based on its load profile which is
monitored by the Building Automation Computer. "Literally at any second in time, you
can see how much electricity is being consumed and this is averaged out over the months to
create a 'common load profile' which draws a picture of the peak demand over the day. The
peak can be shifted outside of Eskom's peak time, when the air conditioning plant, for
example, is started up earlier and the building pre-cooled to a much lower temperature
between 7 and 9 am, before people arrive and start turning on lights. This means that
during the peak period chillers can be shut down and a comfortable temperature will
continue to be maintained. This is known as load shedding, " says Smith.
"Another
way in which we can work towards negotiating the tariff which suits our profile best, is
by load rolling. We don't want all the air conditioning fans to be switched on at the same
time, creating a peak which is costly - so we roll the load. We switch on the first fan
and then wait half and hour before we switch on the second, then we wait another half an
hour before we switch on the third and so on. We do the same with lights and this is much
less costly. If we switched on all the lights on 20 floors at the same time, we would get
a massive peak."
Megawatt
Park has installed the Metatel System, as add-on software to the Building Automation
System, for controlling the lights. Every floor is divided into 24 sections and each
section has its own code. If someone is working overtime, he dials in and gives his code
and the lights in his section only are turned on for an hour. The lights flash a warning
five minutes before they go out and by dialing into Metatel again, another hour's worth of
light can be ordered. On a working day morning, the lights in each section are scheduled
to come on one minute apart, so that no peak is created and this results in huge savings.
In 1985,
Megawatt Park's electricity bill was R 700 000 a month and in 1999, it is only R 300 000 a
month. This is in spite of a 40% growth in electricity consumption over that time period,
because of the increase in the use of machines - computers, printers, photo-copiers and
faxes.
In 1998,
after joining the Green Buildings programme, every light fitting in the building was
replaced with an electronic ballast and a triphosphor tube, over a six month period. This
lighting has proved its energy efficiency: in January 1997, 3 799 075 kilowatt hours were
recorded, while in January '99 only 2 521 407 were recorded. At the same time, variable
speed drives were installed on the twenty two large air conditioning fans, so that the
speed of these fans can be adjusted according to need. The capital cost of the new light
fittings and the variable speed drives was R 5 million and this will be paid back over 2,4
years, in electricity savings. All the perimeter lights have been fitted with energy
efficient compact fluorescent lamps (CFL’s)
-----
FEATURES
1999 Ilasa Awards
The
Institute of Landscape Architects (ILASA) confers Merit Awards on its members for
outstanding work carried out in all spheres of landscape architecture and environmental
planning. Only the very best work is recognised based on the criteria of thorough
analysis, problem solving, innovation, sustainability, timelessness and relevance. Nine
entries were received this year from landscape architects in Gauteng, Western Cape and
KwaZulu-Natal.
The work was
adjudicated by the following panel: Alan Cave (landscape architect and national
adjudicator), Prof Michael Murphy (landscape architect), Bernie Oberholzer(landscape
architect), Brian Stokes (landscape architect) Piet Vosloo (landscape architect), Rudolph
van Rensburg (architect), Ludwig Hansen (urban designer) and Chris Brooker (civil
engineer). Three Merit Awards were given to OVP Associates Landscape Architects for Table
Mountain Cableway Upgrade, Bloubergstrand Beachfront Upgrade and Khayelitsha Open Space
Study; while Newtown Landscape Architects won an Award for the Visual Environmental
Assessment of Sibaya Resort; and Frans Jordaan, Peter Velcich and Willem van Riet for the
SA Manual for Outdoor Advertising Control.
Table Mountain cableway
upgrade
Landscape architects: OVP Associates
Client: Table Mountain Aerial Cableway Company
The upgrading of the existing facilities related to the cableway on Table
Mountain, which has National Monument status, represents a major environmental achievement
resulting from the close collaboration of consultants, contractors and client, under
severe constraints. Since the cableway was opened in 1929, 11 million people have visited
that part of the Mountain, placing extreme pressure on existing facilities and on the
neighbouring environment. In 1992, the decision was taken to increase the capacity of the
cableway and to improve access.
At the
summit, both environmental and logistical issues had to be addressed. The existing network
of pathways was ill-defined and visitors deviated from these at random to reach viewing
spots, with detrimental impact on both vegetation and rock formation ecology. Unsightly
structures had been erected on the western table over the years. OVP participated in both
the broad planning and the detailed design of the external environments of the Lower and
Upper Cableway Stations. To enhance the visitor's mountain experience, unattractive
structures were demolished, the pathway system restructured and viewpoints constructed.
A process of
Integrated Environmental Management was followed and interested and affected parties
contributed to the planning, ensuring that the environmental consequences of the proposals
were adequately addressed. An Environmental Management Plan was then formulated and, in
accordance with this, method statements of work to be carried out had to be approved prior
to construction and all the work on site was monitored by a full-time Environmental
Control Officer. 'No-go' areas were established to protect vegetation and rocks.
Construction techniques were adapted to protect the environment.
The hard
landscaping components on top of the mountain included exposed aggregate concrete
pathways, sandstone walls, steel walkway bridges, steel viewing decks and concrete light
bollards. At the Lower Cable Station, the new components included retaining walls,
concrete light bollards and surfacing of the precinct and parking area. The new sunken
reservoir, services and existing septic tank were incorporated into the overall landscape
concept.
The soft
landscaping entailed the rehabilitation of areas, affected during the construction period,
with local indigenous plant species, as well as the reinstatement of vegetation where
existing pathways had been demolished. The philosophy behind the rehabilitation of the
vegetation was to restore as many of the existing plant species to the disturbed areas as
possible, with the emphasis on a managed recolonisation by seed. The more visible areas
immediately adjacent to the two Cable Stations were planted with transplanted and
propagated species. All the propagation, growing on and hardening off was done at a
nursery under very stringent conditions to prevent contamination with other plant species,
in accordance with approved method statements. Collection of seed and cuttings started on
the mountain well in advance of construction - and this was an on-going process, as
various plant species produce seeds at different times. Plants were planted out on site
during April 1998, so that they would benefit from the winter rains, as irrigation was not
acceptable.
(See article
'Taking tourists to the Table Top' in Jan/Feb 1998 issue of The Urban Green File.)
Project team
Client: Table Mountain Aerial Cableway Company (TMACC)
Architects and principal agent: MLH Architect & Planners
Landscape architects: OVP Associates
Civil & structural engineers: Hawkins Hawkins & Osborn
Mechanical & electrical engineers: CA du Toit
Environmental consultants for TMACC: Crowther Campbell & Associates
Environmental management consultants for South African National Parks: Gibb Africa
Cableway contractors: Garaventa (Switzerland)
Interior design: The Design Company
Project manager and civil contractors: Murray & Roberts Cape Ltd
Landscape contractor: Garden Life
Propagating nursery: Good Hope Nursery
Judges' appraisal
This project exemplifies invisible design. The sensitivity of the area and
its importance as a tourist attraction and ecological resource have been so cleverly
handled that the end result belies the amount of effort and attention to detail that have
gone into recreating a very natural mountain top environment. This can only be truly
appreciated in comparison to the previous condition of the area. Its value lies in a
successful extension of access to previously restricted areas and the simplifying of the
previous labyrinth of pathways. Circulation has been made direct and simple so that the
user is not confused about direction while exploring the summit. There is a consistent and
integrated design approach throughout the various aspects of the project and this promotes
legibility and reflects coherence at both planning and aesthetic levels. There has been
good use of materials and detailing, although, it must be mentioned, that one of the
judges thought that the design of some of the elements - the balustrades, viewing decks,
lighting and signage - was out of context and competed with the rugged timelessness of the
mountain.
Bloubergstrand
beachfront upgrade
Landscape architects: OVP Associates
Client: Bloubergstrand Local Council
The classic view of Table Bay is traditionally presented from the historic
coastal village of Bloubergstrand. However, a century of ad hoc development, with limited
attention being paid to coastal erosion and little concern for the beach user's
convenience, had led to a degraded and unappealing beachfront area. Concern about the
pressures of urban growth and a burgeoning tourist industry resulted in a co-operative
project between the Cape Metropolitan Council and Bloubergstrand Local Council to initiate
a process of beachfront upgrading. OVP was initially appointed to prepare a Beachfront
Management Plan in consultation with the local community and interested parties to serve
as a guide for future actions. The planning process addressed issues ranging from public
perceptions, protection of the coastline, vehicular and pedestrian movement, public
amenities, park furniture, general landscaping and maintenance, budgeting and project
phasing.
The first
phase development was focussed on the shaping of a 'gateway' to Bloubergstrand. Works
included the re-shaping and revegetation of a kilometer of the primary dune system, with
back of beach amenities, parking areas and a coastal walkway. In phase two and three, sea
walls, slipways, steps and terraces were combined to form a 2km meandering promenade along
the shoreline - protecting parking, grassed areas and other amenities from wave erosion.
The aim was to design the hard edges to be multi-functional and as an appropriate setting
for user enjoyment.
After
consideration of various materials for the sea walls and promenade, concrete was chosen
for its inherent physical properties and aesthetic qualities, as the most appropriate
interface material between land and sea. A finish of exposed sandstone aggregate was
chosen. The colour, texture and pliability of the concrete means that the material blends
with the beach sand and the rocks. A sense of continuity has been achieved within the
diversity of shapes that resulted from site constraints and functional needs. Precast
concrete elements, such as seating, waste bins and bollards, were also designed with
similar surface finishes.
The
challenge was to design and construct these concrete elements in a sensitive but often
unfriendly environment. A particular difficulty was to balance the unpredictable nature of
the ocean forces with the unwavering constraint of the client's budget!
Project team
Client: Bloubergstrand Local Council
Landscape architects/architects: OVP Associates
Civil engineers: Africon Engineering International (Pty) Ltd
Electrical engineers: Du Toit & Van der Vyfer
Contractor: Greymo Construction
Judges' appraisal
Beachfront designs have to address the high energy interface between the
sea and the land. In this case, the project was complicated by the proximity of the urban
context. Properties were periodically threatened by high seas. There has been competent
conceptualisation of this problem in relation to the environment and a commendable
solution has been presented. The detailing is refined and yet restrained, and the linkages
between the various areas where open space interacts with the beach have been comfortably
addressed. The well-designed pathways and sea wall effectively link spaces along this
fragile and energetic edge, allowing for safe promenading in a pleasant and organised
fashion. A closer examination of details revealed materials which would be unlikely to
withstand the coastal environment and could be subject to vandalism, such as the paint
which was used on the seating walls at the children's play area and was already peeling,
and the clearly visible irrigation boxes. Nonetheless, this project has had a significant
influence on the quality of the sea/urban interface along Bloubergstrand.
Khayelitsha open space
study
Landscape architects: OVP Associates
Client: City of Tygerberg
OVP Associates was appointed to undertake an Open Space Study of Khayelitsha
and to prepare an Open Space Framework. In conjunction with the Study, OVP was appointed
to design and implement the development of two parks, Keric and Macassar, in Khayelitsha.
(See article 'Two parks in Khayelitsha' in Jul/Aug 1998 issue of The Urban Green File.)
The latter process served to inform the Study through invaluable hands-on experience. The
Study revealed that the definition, role and value of open space is changing, in this time
of rapid change in South Africa.
Claims have
been made that the major problem in South Africa is not housing, but rather the context
within which housing is placed. This 'context' relates to the public domain, which has
received little to no attention due to spatial segregation as a result of mono-functional,
programmatic and separated land use planning, as well as social separation as a result of
politics. The public domain is spatially represented by open space.
The sterile
nature of the large expanses of open land, which exist within the urban structure, does
nothing to promote a rich public domain, social dimension or opportunity for conservation
of natural resources. Open space, within this study, includes the land use zoned as public
open space and sportsfields, road reserves, public squares and vacant or undeveloped land
which has the potential to be rezoned as public open space. The environment of Khayelitsha
is people-centered and open space should, therefore, create an environment which
facilitates and enriches the daily activities of people - and not merely be seen from a
conventional viewpoint as space set aside for recreation and conservation of the natural
environment. The development of open space should aim to structure the urban environment.
The planning
and developing of this space necessitates an integrated and sustainable process resulting
in an integrated and sustainable product. Agenda 21 states that economic and social
development and environmental protection are interdependent and mutually reinforcing
components of sustainable development. The success of the development of any open space
hinges on its ability to be socially, economically and environmentally sustainable.
Against a
background of poverty, high unemployment and shortage of adequate housing and private
space, the sustainability of natural resources will be low on the list of priorities.
Enhancing the productive capacity of people and improving their access to sustainable
livelihoods increases both their individual well being and that of their communities - and
only then is participation in resource conservation and environmental protection
facilitated. Set within the broader context, the sustainability of open spaces relates to
the strengthening of local capacity, the involvement of the community in management and
maintenance issues and the creation of private/public partnerships for the development of
projects.
This
approach promotes a new type of landscape: a productive landscape - treating the landscape
within the urban context as a productive resource from which users will be able to
generate an income. A new relationship is thereby formed between people and the land which
must provide for them in the future and which they must conserve.
The
objectives of the Khayelitsha open space study were:
•
to investigate the
context of open space within Khayelitsha and identify potential opportunities and
•
constraints with the
intent of informing open space planning and development;
•
to formulate a clear
definition and vision, and clear principles, goals and guidelines for open space planning
and development;
•
to formulate an
integrated and sustainable Khayelitsha Open Space Framework;
•
to propose an
implementation strategy at regional and district levels;
•
to provide a
sustainable process for the development of open space; and
•
to make key
recommendations concerning the establishment and sustainability of the Khayelitsha Open
Space Framework.
Acknowledgements
City of Tygerberg
Leaders and community of Khayelitsha
Macroplan
Liebenberg & Stander
Wesgro
University of Stellenbosch: Sociology Department
Ninham Shand
Judges' appraisal
This study addresses the ever-present concern with improving the spatial
quality of townships. The study has been done in a thorough and convincing manner and
involves pioneering work in open space development in townships - it provides a workable
solution for a major urban problem. The copy of the report, received by the adjudicators,
was poor in the areas of legibility of graphics and photographs, and in its flimsy binding
- all of which detracted from its communicative ability. However, the quality and extent
of the research is impressive and the study will effectively add to the body of knowledge
on the subject which will benefit planners, architects and landscape architects.
Sibaya resort and
entertainment world
Landscape architects: Newtown Landscape
Architects
Project proponent: Afrisun KZN (Pty) Ltd
People are becoming constantly more aware of the fact that they can voice their
opinions about environmental and aesthetic matters when new developments are proposed. One
of the main concerns is the visual impact that development will have on the landscape.
What is visually acceptable and what is unacceptable is largely a subjective matter and
the public is demanding that visual issues be dealt with in a meaningful way. The
understanding of scenic beauty is heavily influenced by personal preference but the
factors involved in evaluating the visual quality of a landscape and the impact that a
development will have on it are considerably more complex.
The
assessment of visual impact is not a purely scientific study, as are the methods of
determining increased noise levels or traffic volume. Consequently, a technique that takes
into account both objective and subjective factors must be employed. Newtown Landscape
Architects have designed a methodology which can be used to quantify the more objective
factors. The visual impact of a new development is measured as the change to the landscape
caused by its physical presence and the magnitude of that change - that is the degree to
which that change compromises, enhances or maintains the visual quality of a particular
area.
The layman's
concerns are whether he will be able to see the new development, what it will look like
and whether the development will compromise views in the area. It is, therefore,
imperative to depict that change in as realistic a manner as possible. The method is
guided by the following objectives: to describe the character, quality and sense of place
of the landscape (visual resource); to establish the areas from which the development is
visible (visibility and exposure); and to simulate visually the physical presence of the
development (visual intrusion).
The first
two objectives are relatively easy to achieve, while the third is more difficult and it is
in this area that the public have lost faith in so-called specialists. 'Artistic
impressions' of proposed developments are seldom accurate and they fail to represent the
development visually in its true context, resulting in misinterpretations and unrealistic
expectations. The use of a photographic simulation technique, depicting an accurate
characterisation of the resulting change to the landscape addresses this concern. The
technique produces a realistic, authentic and clear picture of what people are really
going to see and this virtually eliminates areas of uncertainty that often become
emotional issues.
(See article
on 'Photographic simulation' in Mar/Apr 1999 issue of The Urban Green File.)
Judges
appraisal: The subject of visual assessment, which is usually considered to be largely
subjective, has been clearly and rationally set out using a sound philosophical basis and
sound criteria for evaluation. The high standard of the digitised photographs and maps are
an aid to communication and the use of computer generated images to present the visual
extent, although certainly not a new technique, has been effectively managed. The study is
presented in a clear and logical manner and, although it was felt that some of the
conclusions were debatable and the recommendations could have been more direct and
specific, the report will add to the body of knowledge on visual assessments.
South African manual
for outdoor advertising control (SAMOAC)
Landscape architects: Frans Jordaan, Peter
Velcich and Willem van Riet
Client: Department of Environmental Affairs and Tourism
The importance of the visual environment is often underestimated or seen as an
elitist concern and to recognise its real value, it should be measured against the
background of the tourism industry. Visual resources such as scenic landscapes and
cultural streetscapes constitute major tourist attractions. The visual environment can be
seen as the fabric that gives meaning and substance to any tourism experience. Each
country, area, city or town has its own unique visual character. In South Africa, with its
richness and diversity of landscapes and cultures, it is of utmost importance that the
element of local character should be enhanced wherever possible. There is a real need for
visual resource management in South Africa because of the importance, as a revenue source
and employment base, of the SA tourism industry.
The visual
environment also plays an important role in creating better human living environments for
all communities in SA. It is the key to ensuring mental health and psychological well
being. It has an immense impact on how we think and act as human beings. Research has
shown that the visual environment has a definite influence on human behavioural patterns
such as the productivity of office workers, vandalism and the crime rate. It also plays an
important role in creating healthy communities. A sense of place and identity is created
by means of the visual environment and this leads to a sense of security and permanent
belonging, community pride, human dignity and enthusiastic citizen involvement.
Outdoor
advertising and information transfer fulfils an essential function in modern society. It
contributes to economic growth. However, if outdoor advertising - which comprises all
signs, varying in size from large billboards to small placards and posters, erected or
displayed outdoors to provide information - is not controlled properly, it could have a
negative impact on tourism resources and the human living environment. Negative impacts
have been experienced in countries such as the United States of America. The need has been
expressed by the outdoor advertising industry that control measures should be revised in
order to arrive at measures that are more representative of the needs and lifestyle of
modern society. Seen against this background, SAMOAC is aimed at providing an efficient
and effective framework and guidelines for outdoor advertising control in SA.
In applying
these guidelines, controlling authorities and the advertising industry alike should strive
to strike a balance which will allow for advertising opportunities and economic
development, on the one hand, and traffic safety and the conservation of visual resources,
on the other. Instead of being detrimental to the visual environment, outdoor advertising
should be used in a manner that adds to the aesthetic appeal of urban streetscapes. This
is an enormous challenge for the outdoor advertising industry!
The manual
constitutes only a framework and guidelines for control. Municipalities who wish to
publish advertising by-laws may have to adapt the manual to suit their specific needs. A
basic legal and technical check has been done on this document to minimise any possible
vagueness or ambiguity in the interpretation thereof and to facilitate the drafting of
by-laws.
(See related
articles in The Urban Green File: 'Outdoor Advertising - urban art form or visual
pollution?' and 'Arrogant, disrespectful advertising' Mar/Apr 1998 issue; 'Some pleasing
billboards and some hideous ones' May/June 1998 issue; 'Details in the urban environment'
Jul/Aug 1998; and 'An attempt at continuity' Sep/Oct 1998.)
Judges'
appraisal: In the context of the ever increasing visual pollution of our landscape, this
well researched and concisely presented document provides very useful reference material.
The information is produced in a lucid and user-friendly manner which makes it
comprehensible to a wide audience. It provides immediate access to and understanding of
the entire scope of signage in the landscape. The thorough classification and regulatory
system is well presented, although somewhat vague on specifics such as scale and detail,
which may give the unscrupulous outdoor advertiser or municipality a way out in a number
of cases. Good use has been made of colour photographs but more diagrams as an additional
visual aid would have been useful. Nevertheless, this document contributes significantly
to the knowledge base on this subject.
-----
Stormwater harvesting
New
legislation and the right to water
The
philosophy behind the new water laws recognises only two basic rights to water. The first
right is the subsistence or survival requirement of people, set at 25 litres per person
per day, and the second right is that of the environment. The law makers have recognised
that if the environmental and ecological demands of our rivers and wetlands are not met,
in terms of quantity, quality and time distribution of water, they will degrade to the
extent that the system will be incapable of meeting the other demands that a socially and
industrially developed society will place on it.
This
represents a radical change in the allocation and cost of water to consumers. The old
right that riparian landowners had to an automatic share of water from their river has
fallen away, as have the distinctions between private and public water and between normal
and surplus stream flow. Water is now allocated through a system of licences and permits
that can be revoked if the water is wasted or if there is a more pressing need elsewhere
in the catchment.
The law also
recognises that water, even in its raw form, has a value and so must be bought at a cost
appropriate to that value. Almost all of our water supplies require treatment and
transport from the point of supply to the consumer, invariably meaning a substantial
investment in infrastructure and operating costs. So the principles of "user
pays" and "who drives the marginal demand should pay the marginal cost"
come into effect and, for the first time, consumers are being asked to buy the commodity
at a cost related to its true value.
The cost of water
While these principles are laudable, they do have serious cost implications when large
quantities of water are required for irrigating landscaped gardens or sports facilities.
Golf courses have especially high water needs. Clearly, irrigation water requirements vary
greatly depending on factors such as the type of planting, the characteristics of the
soil, growing or dormant seasons, air temperature, humidity, evaporation rate and
geographical location. But, for the purpose of this article, a Gauteng rainfall pattern
and the rule of thumb, that good quality turf needs 25mm of usable precipitation per week
when growing and about 10 mm per week when dormant, will be assumed. Local authorities in
Gauteng currently charge consumers about R4 per kilolitre of water, so it costs about R10
per week to irrigate 100 m2 of turf using domestic water.
Rainfall
does not provide as much as water as one would expect - mainly because it is not evenly
distributed or really accumulative. Much of our rain falls as light showers of 1 - 2 mm a
day which does not really benefit the plants, or as heavy storms when most of the water
runs off into streams. In our summer weather pattern, wet and dry spells are interspersed.
We often get wet spells of three or four days when 50 to 100mm of rain falls, but this
rain only satisfies the irrigation need for about a week afterwards. As a typical example,
the rainfall pattern at Zoo Lake in Johannesburg over the 20 years from 1959 to 1979,
manifested the following characteristics:
•
40% of the days had no
rain on that day or on the preceding 6 days - that is, 40% of the weeks were dry
•
78% of the days had
less than 25 mm of rain on that day or on the preceding 6 days - that is, some irrigation
would be required in 78% of all weeks
•
15% of the days had 50
mm or more of rain on that day or the preceding 6 days - that is 15% of the time too much
rain fell to be of benefit from an irrigation point of view
•
(Darryl - no need for
this smaller point size, above - or leave it small and box it.)
•
A detailed analysis
carried out using the above Zoo Lake data to determine the likely irrigation requirements
for the short golf course at the Fourways Golf Park gave the following results:
•
Average annual
irrigation depth required - 1040 mm
•
Average annual
rainfall - 778 mm
•
Theoretical deficit to
be made up - 262 mm
•
Actual deficit because
of time distribution of rain -500 mm
•
that is only about 65%
of the actual rain is effective for irrigation.
In this
particular instance the area to be irrigated was about 2,6 ha and the difference between
the theoretical and actual deficit of 238 mm represented an annual cost of about R25 000
at the present day water cost of R4 per kilolitre.
Availability of water
One of the ways of reducing this deficit is to collect the stormwater that
would otherwise run off the site in times of high rainfall and to store it for later use
during dry periods - a process known as stormwater harvesting. While the main objective of
harvesting stormwater is to increase the efficiency with which the rain falling on the
site contributes to the water requirements of the vegetation on the property, the
secondary benefit of flood attenuation is often achieved.
The easiest
technique is simply to divert runoff from impervious areas onto grassy patches before it
is collected into the drainage system. Rain that falls onto paved areas or roofs seldom
contributes to the irrigation requirements on the site - the water is usually collected in
the site drainage system and directed off the property as quickly and efficiently as
possible. Directing this runoff onto grassed or other planted areas gives at least some of
the water an opportunity to infiltrate into the ground.
The next
level of complexity would be to divert the runoff into swales or french drains filled with
a porous medium such as clean crushed stone. A substantial volume of stormwater can be
retained on site after each storm and the rate at which it percolates into the ground will
depend on the permeability of the soil. If located close to trees or other deep rooted
plants, these drains will not only contribute directly to the water needs of the plants,
but help with groundwater recharge. It is, however, imperative not to locate soakaways of
this type close to roads or buildings where saturation of the soils may cause foundation
problems.
These
passive methods can be very effective, particularly if carefully designed and distributed
around the site - but a far greater level of efficiency can be achieved if the water is
stored and actively distributed, either via a high pressure spray irrigation system, a low
pressure drip system or a simple surface flooding system.
The first
step in the design process is to determine how much runoff can be collected and stored and
this depends on the efficiency of the collection system, the volume of the reservoir
available for storage, the characteristics of the rainfall pattern at the site, and the
demand that is likely to be made on the stored water. Any rational design must provide a
balance between these factors and the cost of the harvested water compared to the cost of
water from an alternative source, for example a borehole, the municipal potable water
system, or even treated effluent.
For
impervious areas such as roofs or roads, the volume of runoff is calculated as follows:
•
Volume (m3)
= Area of catchment (m2) x (Depth of rain less initail abstraction (mm)) / 1000
•
The initial
abstraction is the depth of rainfall that is required to wet the surface, fill small
depressions, etc - typically between 0 mm for smooth sheeted roofs and 2 mm or 3 mm for
brick paved roads.
•
Therefore 100 m2
of roof will yield 1 m3 of runoff per 10 mm of effective rain.
Quite
clearly the greater the volume of the reservoir, the greater the proportion of runoff that
will be trapped - but the law of diminishing returns plays a part. Table 1 shows that more
than half of the total rain on the Highveld falls on days with less than 20 mm of rain and
more than 80% on days with less than 40 mm of rain, so it may not be cost effective to
provide storage to trap the large volumes of runoff that occur on very wet days.
Similarly, expenditure to enhance the runoff from small depths of rain would hardly be
worth the effort here as less than 10 percent of the total rainfall occurs on days with
less than 5 mm of rain. The greatest benefit would come from concentrating efforts in
trapping the runoff on days where between 5 mm and 40 mm rainfall occurs, as this
represents 72% of the total available runoff.
A reasonably
cost effective stormwater harvesting system in Gauteng could therefore be expected to trap
about 70% of the average annual rainfall or about 40 to 50 m3 of water per 100
m2 of catchment.
These
statistics are not true for all localities as rainfall patterns differ radically across
the country and each site must be assessed individually. Daily rainfall records for almost
any locality in the country are available from the South African Weather Bureau. It is
essential that a sufficiently long time period be analysed to ensure that the results are
statistically representative. The Zoo Lake statistics given above are based on 40 years of
data from 1959 to 1999.
The demand
placed on the stored water and the strategy for its use will also have an effect on the
total volume of water that needs to be stored. If extraction occurs frequently then it is
more likely that the water level in the reservoir will be drawn down, leaving storage
available for the runoff from the next storm. A typical system would use a relatively
small reservoir to supplement irrigation water requirements in the dry periods between
rainy days of a typical Highveld summer.
A stormwater
management system that is designed with harvesting in mind will also have a significant
flood control benefit. Increasing imperviousness in a catchment has two major impacts of
nearly equal significance. The first is of course the increasing volume and rate of
runoff, but the second, often ignored, impact is the increasing frequency of runoff.
Paved areas
may not have as great an impact on the runoff from big flood producing storms as would be
expected. Paving has three effects: it makes the ground surface impermeable thereby
preventing infiltration; and it makes the surface smooth, which reduces the depth of rain
necessary to initiate runoff and increases the hydraulic efficiency of the catchment, so
that water runs off much more quickly. The time of concentration of the catchment is
reduced, so decreasing the duration and hence increasing the intensity of the critical
storm.
But these
very intense storms seldom occur in isolation, they often follow less intense rainfall and
land on an already saturated catchment where even grassed or other vegetated surfaces
offer minimal opportunities for infiltration or other losses. The decreased time of
concentration is therefore an equally significant impact to the increased runoff
coefficient that results from paving, so techniques to reduce the hydraulic efficiency of
the drainage system, and return the time of concentration to its pre-development value,
may be mitigation measures that are as effective against big floods as attempts to
increase the permeability of the paved areas.
Increasing
emphasis is, however, being placed on the damage that the increased frequency and
intensity of spate flows does to stream morphology and ecology. In addition to being a
major cause of channel erosion, these spate flows cause very sudden changes in the
physical environment of the stream. Water depths and flow velocities change rapidly and
because sediment load increases rapidly during the rising limb of the hydrograph, this
results in the sudden deposition of a silt blanket as the spate subsides and an almost
instantaneous drop in water temperatures as the cold rainwater hydrograph churns up the
warmer base flow.
These spates
follow short intense storms, often with a total precipitation of 5 mm to 10 mm - meaning
that any stormwater harvesting system that intercepts the runoff from these events will
have a very significant environmental benefit for the urban stream.
Control of Water
A typical stormwater harvesting system comprises four major components: a
catchment, a collection system, a reservoir, and a distribution system.
Urban
catchments are usually roads, parking areas or roofs, all of which present water quality
problems. Roofs generally yield the best quality water but some care is still required.
The first flush after a long dry period is likely to carry with it a substantial load of
muck in the form of fall-out from the air. Care should be taken in industrial or mining
areas where this dust can be heavily polluted. Some roof paints also contain chromium or
lead that is toxic and yields a runoff totally unsuitable for domestic use.
Parking
areas and roads can yield a runoff that carries a significant load of oil, rubber and
heavy metals, most notably lead, as well as a large amount of sediment. Oils and
detergents that escape when cars are washed in domestic and office parking lots can cause
problems - foam from detergents in high concentrations can cause pumps to fail. Some
pre-treatment of the water, such as running it over a grass swale can be beneficial and
provision must be made to divert runoff away from the reservoir in the event of a chemical
or oil spill.
Collection
systems typically comprise pipes or channels that flow under gravity to the reservoir, but
sometimes more elaborate techniques are required. Open channels are preferred in gravity
systems because they are hydraulically less efficient than pipes, they are less
susceptible to blockages, easier to clean if blockages do occur, and easier to control in
the event of a disaster such as a chemical spill in the catchment. With careful design,
channels can also be used as sediment traps to prevent degradation of the reservoir
capacity. Particular care must, however, be taken in the design of channels on steep
sites. Super-critical flow, likely to prevail in all lined channels with a gradient
steeper than about 1%, does not easily turn corners.
Elaborate
systems - such as at the Fourways Golf Park where the site layout has placed the primary
reservoir at the top of the hill and stormwater collected in sumps at two corners of the
site has to be pumped up to the pond in the golf course - require very carefull design to
balance runoff, sump size, pump capacity, and reservoir volume. Such an installation is
likely to require detailed modelling based on real historical rainfall data to achieve a
cost effective design.
It is
generally desirable to introduce a sediment trap into the system immediately upstream of
the reservoir. Common designs are an access chamber with a deep sump below the pipe inlet
and outlet, or a wide shallow grassed or reeded channel. It is most important that the
trap can be cleaned out easily. A channel should have a hard lining such as 'Armorflex'
defining its bed and a sump should be provided with a large opening to give accessibility
to a suction pump. While the choice of trap is often dependent on site constraints, two
major shortcomings of sumps should be recognised: firstly the trap will be "out of
sight - out of mind" and not likely to be cleaned unless a programmed maintenance
schedule is implemented and, secondly, the sump will always contain a volume of stagnant
and often smelly water.
The choice
of reservoirs will also depend on site constraints and the intention of the designer, as
well as the size of the catchment area supplying them. In Gauteng, a typical yield would
be about 50 m3 of water per 100 m2 of catchment area - and
reservoirs should be sized accordingly
Open ponds
can be designed to serve both aesthetic and utilitarian functions on the site. Depending
on the soil type and the value of the water being stored, the pond can be left unlined, in
which case some seepage loss can be expected If the pond is lined, the only losses will be
evaporation and draw off. The most common linings are geomembranes, such as a thick
polyethylene sheet or geofabric impregnated insitu with a rubber bitumen emulsion, or clay
modified soils (usually a percentage of bentonite mixed into a soil layer below the bottom
of the pond). Other lining materials, such as butyl rubber, ethylene vinyl acetate
copolymers, and a bentonite filled geofabric (Bentofix) are available for difficult
conditions. They are, however, costly and may be susceptible to damage by UV exposure. All
linings should be protected by at least 150 mm of soil for aesthetic, durability and
safety reasons.
Evaporation
losses from open water surfaces can be significant. On average the loss varies between 100
mm and 150 mm per month depending on the time of year - but it could easily be double this
on a particularly hot, dry summer month when the stored water is most valuable.
Buried or
above ground concrete or brick structures are useful where space is restricted, but they
are expensive to construct and require the design services of a structural engineer. Long
brick walls are not very stable and even low walls should be braced with cross walls
spaced at not more than twice their height. Open topped, vertical sided tanks are
generally not a viable option for both aesthetic and safety reasons.
A pit, lined
with thick plastic sheeting and filled with large boulders, makes a fairly economical
below ground storage reservoir. The boulders provide stability to the soil walls and,
depending on their size and shape, provide for a usable water capacity of about 30% of the
volume of the excavation. The plastic liner can be closed over the top of the boulder
filled pit and covered with any depth of soil without incurring a structural cost penalty.
A reservoir of this type is, however, almost impossible to clean, so careful attention
must be paid to protecting it from an accumulation of sediment.
For small
domestic applications, concrete manhole rings sunk into the ground as a caisson can be
used to build a quick and very effective sump. If the perched water table is shallow the
bottom of the shaft can be covered with a layer of crushed stones to permit infiltration
and create a well. If, however, water is likely to be lost from the sump into the soil,
the shaft can easily be waterproofed. A properly compacted concrete slab about 150 mm
thick poured into the bottom of the shaft will form an effective plug, and a variety of
bandages are available for sealing ring joints. Many of these products are solvent based
and extreme care must be taken when using them in confined spaces, as the vapours can be
narcotic, poisonous, and explosive.
Extracting water for
irrigation
Depending on the volume of water available and on the sophistication of the
system there are a number of ways in which water can be extracted from the storage sump
and used for irrigation.
The
simplest, where only small volumes are involved, is manually by bucket, hand pump, or by
gravity if the tank is above ground - but this is hardly viable except in small domestic
or cooperative farming applications.
Supplies to
individual trees or some sort of flood irrigation system can be fed by a low pressure
submersible pump. Small submersible pumps that run on a single phase electrical supply are
readily available. The simplest have a flexible hose connection and are manually
controlled with an on/off switch. They can be suspended on a chain or rest on a stand on
the bottom of the sump.
Spray
irrigation systems require much higher pressures and these cannot easily be generated by
typical open impeller submersible pumps. Multistage borehole pumps work well in this
application as they do not require an elaborate intake system, but a dry well fitted with
a suitable centifugal pump is simple to construct and will work equally well. A single
stage centifugal pump can be started against a closed valve in its delivery line and run
safely in this state for some time, but a multistage pump will soom overheat and damage
itself.
-----
Reviewing the latest billboards
Outdoor
advertising in the urban environment
In the
March/April 1998 issue, The Urban Green File awarded its 'Insult to the Urban Environment'
to the vast, free-standing billboard on Hyde Park Corner in Johannesburg - not just for
its sheer, insulting size but because it obscured the well-known, sweeping vista across
the suburbs of Sandton and Randburg from that point. There was a public outcry about this
and other mega-billboards on the major arterials - and Primedia Outdoor is one of the very
few outdoor advertising companies that has taken the public's objections seriously. The
massive structure on Hyde Park corner has come down and in its place is a much lower
structure, which alone is good reason to commend the company. Primedia has also taken
responsibility for maintaining the whole road island on which the new structure is erected
- and this deserves a further commendation. The viewpoint is no longer obscured - but what
about the design of the new structure and of the surrounding landscaping?
-----
Re-introduction of
indigenous grasses at Royal Johannesburg
Golf courses
occupy extensive areas of urban open space and, in recent years, recognition of the
environmental value of out-of-play areas has been on the increase. Habitat creation in
out-of-play areas on the older courses is being supported by golfers and greenkeepers
alike, while habitat conservation on new courses, where there is still the opportunity to
conserve natural areas, has become an accepted aspect of golf course design. Not only do
these natural areas attract wildlife, they cut unnecessary maintenance costs and enhance
the aesthetic appeal of the course.
In 1998, the
East Course at Royal Johannesburg, now called Royal Kensington, was reconstructed. One of
the priorities was to install a state-of-the-art irrigation system with the objective of
saving water and for increased labour efficiency. Mark Muller was the golf course
architect and an aspect of his design concept was to move somewhat away from the parkland
approach by creating strong definition between the holes.
Golf course
manager Graham Corbett says the decision to use indigenous grasses in between certain of
the holes, instead of an alternative such as shrubberies, was made for a number of
reasons. It was felt that there was a good contrast between the various grasses - there
were taller and shorter grasses of many different colours and textures and these could be
mowed fairly short or left tall and lanky with a slightly unkempt appearance to create a
natural look. Another reason for the use of indigenous grass species, according to
Corbett, was the desire "...to put back what was there before". He said that
when the courses were originally constructed in the mid 1930s, it was minuted that a
horticulturist from Kew Gardens had recommended that they make use of the natural grasses
on the course.
A third
reason was habitat creation. Royal's long term objective is to bring back a large variety
of bird species and an active environmental committee is involved in long term planning to
achieve this and other environmental objectives. Paul Clarke from 'Back to the Bundu' was
brought in to initiate what was termed a pioneering project to re-introduce indigenous
grassland species into sections of the out-of-play areas of the East Course.
Traditionally,
revegetation has relied on grass seed which requires irrigation and fertiliser for the
initial establishment of the grass. Clarke says that often when the maintenance programme
is terminated, the grassland begins to deteriorate and basal cover is reduced. He makes
use of grass plugs to accelerate the process of succession, a technique which not only
eliminates the chance of poor germination, as indigenous grasses have an inherently low
germination rate, and increases the chance of the plants' survival but requires no
irrigation or fertilisation. Plugs also effectively control soil loss and runoff,
preventing erosion damage.
Grasses were
chosen according to the natural diversity and dominance of species in the area and for
their aesthetic appeal, with colour and volume in terms of inflorescence being important
considerations. Clarke says: "Diversity is the key. We strive to replicate the
natural balance. We need to introduce species, such as the climax species Themeda triandra
(Rooigras), that will create a stable environment and lead to sustainable cover in what
are fairly acid soils. At Royal, it was necessary to strive for a balance between
diversity and aesthetics, and we chose to plant large stands of the same species in
certain areas, such as on the spectator mound where we used clumps of Rooigras
interspersed with strips of the attractive Melinis nerviglumis (Bristle-leafed Red Top)
with its purple-red inflorescence. Monospecific clumps do occur naturally in the
veld."
In areas on
the course, the indigenous grasses have been planted along drainage lines which lead into
the Jukskei River and they will function as a silt trap and filter, ensuring that water of
a better quality is returned to the river. In these areas, Clarke has utilised wetland
grasses such as the tall, robust Arundinella nepalensis (River Grass) which, with its
creeping rhizomes, protects the soil adjacent to rivers from damage by runoff water and
Imperata cylindrica (Cottonwool Grass) which is a water-loving grass that grows on river
banks and also spreads by means of rhizomes, forming dense stands which stabilise the
soil. According to Clarke, both these grasses with their rhizomatous growth habit are
difficult to germinate from seed.
In the areas
chosen for the indigenous grass cover, the kikuyu, which is the fairway grass at Royal,
had to be cut down and sprayed with the herbicide, Roundup, before the grass plugs were
planted . "This was a learning experience for us and we used a small quantity of
2/3/2 fertiliser to help with establishment. We should probably not have done this, as it
encouraged weed growth. Compost might have been a better idea or a slow release organic
fertiliser. We spent many hours pulling weeds out by hand, initially. We also did some
spot spraying to keep the kikuyu out. Now that there is good grass cover, after one
season's growth, the weeds are under control ," comments Clarke.
The veld
grasses will be maintained by means of a single cut or a burn, annually. Clarke says that
the basal cover will need to improve before a burn can be considered or soil erosion will
result. From an aesthetic point of view, Clarke favours burning as close to the start of
the rainy season as possible so that the new green shoots will come up almost immediately.
One of the
most satisfying happenings, since these areas have been grassed, has been the arrival of a
breeding pair of African Black Duck which has taken up residence in the long grass
adjacent to the dam opposite the 15th hole. |
