Eastern False Bay coast aerial view looking somewhat south of east: Gordon's Bay (left) to Cape Hangklip (right)
|Ocean/sea sources||Southern Atlantic Ocean|
|Basin countries||South Africa|
False Bay (Afrikaans Valsbaai) is a body of water in the Atlantic Ocean between the mountainous Cape Peninsula and the Hottentots Holland Mountains in the extreme south-west of South Africa. The mouth of the bay faces south and is demarcated by Cape Point to the west and Cape Hangklipto the east. The north side of the bay is the low-lying Cape Flats. Much of the bay is on the coast of the City of Cape Town, and it includes part of the Table Mountain National Park Marine Protected Area and the whole of the Helderberg Marine Protected Area.
Description and location
The western side is bordered by the Cape Peninsula, and this stretch of coastline includes the smaller Smitswinkel Bay, Simon’s Bay and Fish Hoek Bay. At Muizenberg the coastline becomes relatively low and sandy and curves east across the southern boundary of the Cape Flats to Gordon's Bay to form the northern boundary of False Bay. From Gordon's Bay the coastline swings roughly south, and zig-zags its way along the foot of the Hottentots Holland Mountains to Cape Hangklip which is at nearly the same latitude as Cape Point. The highest peak on this side is Kogelberg at 1,269 m.
In plan the bay is approximately square with rather wobbly edges, being roughly the same extent from north to south as east to west (30 km), with the entire southern side open to the ocean. The area of False Bay has been measured at about 1,090 km2, and the volume is approximately 45 km3 (average depth about 40 m). The land perimeter has been measured at 116 km, from a 1:50,000 scale map.
The bottom morphology of False Bay is generally smooth and fairly shallow, sloping gently downwards from north to south, so that the depth at the centre of the mouth is about 80 m. The bottom is covered with sediment which ranges from very coarse to very fine, with most of the fine sediment and mud in the centre of the bay. The main exception is a long ridge of sedimentary rock that extends in a southward direction from off the Strand, to approximately level with the mouth of the Steenbras River. The southern tip of this ridge is known as Steenbras Deep.
There is one true island in the bay, Seal Island, a barren and stony outcrop of granite about 200 m long and with an area of about 2 ha. It is about 6km south of Strandfontein and is less than 10 m above sea level at its highest point. There are also a number of small rocky islets which extend above the high water mark, and other rocks and shoals which approach the surface. The largest of these, and the most significant navigational hazard in the bay, is Whittle Rock, a large outcrop of granite about half way into the bay and a quarter of the way across from the Cape Peninsula, which is about a kilometre in diameter and rises to within 4 m of the surface. Most of these reefs are granite of the Peninsula pluton, but east of Seal Island they are generally sandstone, probably of the Table Mountain series, though it is possible that some may be of the underlying Tygerberg formation.
The eastern and western shores of the bay are very rocky and even mountainous; in places large cliffs plunge into the water. Notable peaks associated with the bay include Koeëlberg (1,289 m (4,229 ft)), which rises from the water itself forming the highest point of the Kogelberg, as well as Somerset Sneeukop (1590m / 5217 feet) and Wemmershoek Peak (1,788 m (5,866 ft)) which are clearly visible across the bay. The highest peak visible across False Bay is Du Toits Peak near Paarl (1,995 m (6,545 ft)). The northern shore, however, is defined by a very long, curving, sandy beach. This sandy, northern perimeter of the bay is the southern edge of the area known as the Cape Flats. The bay is 30 km wide at its widest point.
Suburbs of Greater Cape Town now stretch right across the Cape Flats from Simon's Town half way down the Cape Peninsula to the north-eastern corner at Gordon's Bay. There are also two small towns of the Overberg region on the east coast of the bay, Rooi-Els and Pringle Bay.
The three main rock formations are the late-Precambrian Malmesbury group (metamorphic rock), the Peninsula granite, a huge batholith that was intruded into the Malmesbury Group about 630 million years ago, and the Table Mountain group sandstones that were deposited on the eroded surface of granite and Malmesbury series basement about 450 million years ago. The sand, silt and mud deposits were lithified by pressure and then folded during the Cape Orogeny to form the Cape Fold Belt, which extends along the western and southern coasts. The present landscape is due to prolonged erosion having carved out deep valleys, removing parts of the once continuous Table Mountain Group sandstone cover from the Cape Flats and leaving high residual mountain ridges.
At times the sea covered the Cape Flats and Noordhoek valley and the Cape Peninsula was then a group of islands. During glacial periods the sea level dropped to expose the bottom of False Bay to weathering and erosion. The last major regression leaving the entire bottom of False Bay exposed. During this period an extensive system of dunes was formed on the sandy floor of False Bay. At this time the drainage outlet lay between Rocky Bank and Hangklip Ridge.
Bartolomeu Dias in 1488 first referred to the bay as "the gulf between the mountains" (Schirmer, 1980). The name "False Bay" was applied early on (at least three hundred years ago) by sailors who confused the bay with Table Bay to the north. According to Schirmer, the confusion arose because sailors returning from the east (The Dutch East Indies) initially confused Cape Point and Cape Hangklip, which are somewhat similar in form. Hangklip was known to the early Portuguese seafarers as Cabo Falso, or False Cape, and the name of the bay derived from the cape.
The climate is Mediterranean, with warm, dry summers and cool, damp winters. In winter gales and storms from the northwest are common and can be ferocious. False Bay is exposed to southeasterly winds in summer and its waters are approximately 6 °C warmer than those of Table Bay, owing to the influence of the warm Agulhas Current.
Marine life and recreational pursuits
False Bay is at the extreme western end of the inshore Agulhas marine ecoregion which extends from Cape Point to the Mbashe river over the continental shelf, in the overlap zone between Cape Agulhas and Cape Point where the warm Agulhas Current and the cooler South Atlantic waters mix. The continental shelf is at its widest in this ecoregion, extending up to 240km offshore on the Agulhas Bank, but is considerably narrower off False Bay. This ecoregion has the highest number of South African endemics, and is a breeding area for many species. There are several important commercial fisheries in this region. The transition between the Agulhas ecoregion and the cooler Benguela ecoregion is at Cape Point, on the western boundary of False Bay.:103
Fishing can be good in False Bay and at times there are large schools of snoek, an oily, barracuda-like fish that is much sought after locally, and Yellowtail. Angling from the rocky shores to either side of the bay is very popular, but can be dangerous. The shape of the bay creates interference patterns in the swells that come in from the Southern Ocean and these patterns occasionally combine to cause "killer waves" to rise up without obvious warning and to sweep the sandstone ledges well above the high tide mark. Scores of fishermen have been swept away and drowned over the years, but this seems to have done little to dampen enthusiasm for the sport.
Sailing is also a popular recreational activity in False Bay. The "killer waves" mentioned earlier can wreak havoc with moored sailboats, especially if the moorings are chain based and on the leeward side when the south-easterly winds are howling up the bay. The sailing clubs in False Bay include False Bay Yacht Club in Simon's Town, Fish Hoek Beach Sailing Club at the main beach in Fish Hoek, Gordon's Bay Yacht Club in the Gordon's Bay Harbour, and Hottentots Holland Beach Sailing Club in Strand.
There is a small granite island in the bay called Seal Island, which is one of the main breeding sites for the Cape fur seal. The seals attract many great white sharks and some of the biggest sharks ever seen have been spotted in these waters. These sharks are famous for the manner in which they breach the surface of the water while attacking seals, sometimes jumping entirely out of the water. Despite this, swimming, surfing, sailing, scuba diving and freediving are popular pastimes around the bay, at centres such as Muizenberg, Kalk Bay, Smitswinkel Bay, Strand and Gordon's Bay. Shark attacks are uncommon but not unknown, with two deaths since 2010.
There are two marine protected areas in False Bay: The Table Mountain National Park Marine Protected Area lies on both sides of the Cape Peninsula, so is partly in False Bay, and the Helderberg Marine Protected Area is off Macassar on the northern shoreline of the bay.
The famous naval base of Simon's Town is situated on the Bay, about halfway down the length of the Cape Peninsula. During the Second World War many heavy guns were dug into concrete bunkers at various points along the mountainous shores of False Bay in order to deter attacks on Simon's Town. The firepower and defensive situation of these weapons were formidable and no attack was ever mounted. Although some of the guns were removed decades ago many large guns are still emplaced on the hillsides near the Redhill road.
Development and human impact
Although urban development of the coast is intense along some parts of False Bay, much of the shoreline remains relatively wild and unspoiled. The bulk of the development is residential; there is little heavy industry. There are a few exceptions, however: one of the largest dynamite factories in the world used to lie near the beach towards the wild and uninhabited eastern end of the bay. The nitroglycerine plant at this installation blew up twice in the second half of the 20th century and sent massive shockwaves across the bay, breaking windows and rattling walls on the distant shores. False Bay is remarkably poor in natural harbours. Almost all protection for shipping and yachts has been created by artificial means (e.g. at Kalkbaai, Simon's Town and Gordon's Bay).
- SAN 1016 - Valsbaai (Map). Cape Town: SA Navy Hydrographic Office. 1978.
- Theron, J.N.; Gresse, P.G.; Siegfried, H.P.; Rogers, J. (1992). Explanation sheet 3318 – The Geology of the Cape Town Area. Pretoria: Geological Survey, Department of Mineral and Energy Affairs, Government Printer. ISBN 978-0-621-14284-6.
- Compton, John S. (2004). The Rocks & Mountains of Cape Town. Cape Town: Double Story. ISBN 978-1-919930-70-1.
- Sink, K.; Harris, J.; Lombard, A. (October 2004). Appendix 1. South African marine bioregions (PDF). South African National Spatial Biodiversity Assessment 2004: Technical Report Vol. 4 Marine Component DRAFT (Report). pp. 97–109.
- Sink, K; Holness, S; Harris, L; Majiedt, P; Atkinson, L; Robinson, T; Kirkman, S; Hutchings, L; Leslie, R; Lamberth, S; Kerwath, S; von der Heyden, S; Lombard, A; Attwood, C; Branch, G; Fairweather, T.; Taljaard, S.; Weerts, S.; Cowley, P.; Awad, A.; Halpern, B.; Grantham, H; Wolf, T. (2012). National Biodiversity Assessment 2011: Technical Report (PDF) (Report). Volume 4: Marine and Coastal Component. Pretoria: South African National Biodiversity Institute. p. 325. Note: This is the full document, with numbered pages.
- "The complete South African Shark Attack Related Incident Record". Retrieved 23 April 2012.
- "Government Notice 695: Marine Living Resources Act (18/1998): Notice declaring the Table Mountain National Park Marine Protected Area under section 43" (PDF). Government Gazette: 3–9. 4 June 2004.
- Declaration of areas as Marine Protected Areas: Government Notice R1429 in Government Gazette 21948 (PDF). 29 December 2000. Retrieved 19 January 2019 – via Centre for Environmental Rights.
- Schirmer, P. 1980. The concise illustrated South African Encyclopaedia. Central News Agency, Johannesburg. First edition, about 211pp.