Download South Africa has a coastline of some 3000km. It stretches from the

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The water environment
WATER RESOURCES:
Marine Water - Coastal Zones
AD3.1
South Africa has a coastline of some 3000km. It stretches from the
Mozambique border on the sub-tropical east coast to the cold
temperate west coast at the Namibian border. This includes a large
number of sandy beaches, rocky shores and sub-tidal reefs interrupted
by estuaries and river mouths some of which are permanently open to
the sea while others are closed periodically.
Climate:
Large-scale atmospheric systems over southern Africa and the Atlantic,
Indian and Southern Oceans control the patterns of weather and climate.
The west coast is characterised by southerly winds and low
rainfall. Along the west coast, rainfall decreases as one moves
north from Cape Town to Namibia (greater than 700 mm to less
than 100 mm).
The south-west coast is subject to southerly winds in summer
and rain-bearing westerly winds in winter. The South coast rainfall
is moderate and variable (400 to 1 000 mm), with a maximum in
the Garden Route area, which experiences year-round rainfall.
The east coast experiences good, summer rainfall, generally
increasing towards Mozambique (800 to 1 300 mm) in the north.
Ocean Currents:
The oceanic setting of South Africa is strongly
influenced by the Agulhas Current and the
Benguela Current System.
The east-west
contrast is seen in the 7°C difference between
the average annual temperature of Port
Nolloth and Durban – both located at similar
latitudes.
The eastern shores are washed by the warm, nutrient-poor
waters of the Agulhas Current that flows south from tropical
latitudes off Mozambique and Madagascar.
The western shores are washed by cold, nutrient-rich waters
drawn up (referred to as upwelling) from deeper layers in the sea.
This upwelling results from southerly winds, blowing parallel to the
coastline and support highly productive marine systems forming the
centre of South Africa’s fishing industry.
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Wave Energy
Most of our coast has a moderate (1-2 m) to
high (2-3 m) wave energy environment and
experiences a predominantly south-westerly
swell direction. The result is an overall
northwards drift along the shores of both the
west and east coasts. This drift transports
between one and two million tons of
sediment past any given point on either
coast each year. About 1 700 km of our
coast is made up of sandy beaches and 1
300 km are either rocky, or mixed rock-andsand shores.
Rivers
Our coast is also strongly influenced by rivers that bring water, sediments,
nutrients and pollutants to the coast.
Along the east coast, short, strong
and fast-flowing rivers drain the steep
slopes.
East of Port Elizabeth, these rivers
carry large silt loads, in excess of 400
tons of sediment per km ² per year.
West of Port Elizabeth, most rivers drain sandstone catchments
and carry much smaller silt loads, typically about 150 tons per km ²
per year (note that some larger catchments, such as the Sundays
and Gamtoos, have sediment yields similar to those of KwaZuluNatal).
Along the west coast, the low rainfall and
flat land result in few rivers that flow all year
round. The largest river, the Orange, drains
half of the country, including the mining and
industrial heartland of the Gauteng area,
and enters the sea at the border of Namibia.
There are no large rivers flowing south into South Africa from
neighbouring states. But there are a few large rivers that flow from
South Africa to enter the sea in Mozambique (e.g. Nkomati and
Limpopo).
Human settlement patterns
South Africa’s coast supports about 30% of its population, and our coast
has one of the highest coastal population densities in Africa about 81/km2,
compared to the average African density of 55/km2.
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Estuaries
Our coast has 343 estuaries. Estuaries are river systems that have, or can
have, contact with the sea. The total area of estuaries in South Africa is
about 600 km2, of which about 400 km2 is along the 570 km Kwa-ZuluNatal coast. Variations in climate, topography and catchment geology give
rise to a wide variety of estuary types in South Africa.
COASTAL AREA
NUMBER OF ESTUARIES
Namibia to Olifants River (407km)
9 estuaries
Olifants River to Berg River (137km)
5 estuaries
Berg River to Cape Agulhas (635km)
36 estuaries
Cape Agulhas to Cape Padrone (815km)
62 estuaries
Cape Padrone to Mtunzini (745 km)
Mtunzini to Mozambique (267km)
TOTAL
225 estuaries
6 estuaries
343 estuaries
(After Heydorn 1989)
Ecology
The South African coast also has a large number (over 10,000) of species
of plants and animals. This comprises almost 15 % of global coastal
species and 12% of these are endemic, that is they occur nowhere else
(DEA&T 1997).
Contact: [email protected] URL: www.waterinfo.co.za
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Copyright: All right reserved
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