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Invented Here and Seen Worldwide – Dolos / Dolosse

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Whale and Dolphin Watching 1 May 2019


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Down to New Brighton Pier, out to sea and along the beachfront

A dolos (plural: dolosse) is a reinforced concrete block in a complex geometric shape weighing up to 80 tonnes (88 short tons), used in great numbers as a form of coastal management to build revetments for protection against the erosive force of waves from a body of water. The dolos was invented in 1963 by South African harbour draughtsman Aubrey Kruger, and was first deployed in 1964 on the breakwater of East London, South Africa.

Up until the invention of the dolosse, large rocks and blocks of concrete were the most common means of providing protection against the notorious waves of South Africa’s eastern coastline. But even these massive and heavy objects could be washed away or moved about, and what was needed was something that was relatively inexpensive but would resist and reduce the force of the waves while remaining in position.

The man generally given most of the credit for inventing the dolos was a harbour engineer at the Port of East London named Eric Merrifield who served at the Eastern Cape port as the chief engineer from 1961-1976. Yet the facts are somewhat different in that Merrifield had little right to such a claim, other than that he was in charge of the engineering office at the time and had signing power for its development. It was, however, his request that set in motion the invention of something that has gone into use across the world as the most successful means ever of absorbing and controlling the energy produced by waves pounding away at natural or man-made areas of coastline.

28-year old Aubrey Kruger, a draughtsman in the employ of what was then the South African Railways and Harbours (SAR&H) was a modest, quiet local man who invented the dolos after commandeering his wife Daphne’s broomstick, from which he cut three pieces of wood which he nailed together in the shape of an H’ with one twisted leg.

His daughter Sandra says her father based his idea on the dubbeltjie thorn.

Krugers idea was that the dolosse, which would be cast in unreinforced concrete, would be placed in front of and on top of each other along the breakwater where they would interlock and, as waves broke against them, would fit even tighter while still allowing some of the waves to pass through the structures, thus weakening their force.

The design of the dolos is not protected by any form of patent. Neither Merrifield or Kruger took the necessary steps to protect the concept.

The reason for this is uncertain. Two reasons for this have been put forward: one by Merrifield; the other by Kruger. Merrifield stated that he did not protect them as he wished them to benefit humanity. Kruger alleges that Merrifield received incorrect legal advice: to wit, that as the blocks had been designed during office hours while he was employed by the State (South African Railways and Harbours Administration), he was unable by law to protect their design.

According to Sandra, the name dolos came from her grandfather, Joseph Kruger, who was a carpenter working at the harbour dry dock at the time. He saw his son and others in the office playing with small models and asked “Wat speel julle met die dolos?” – dolos being the Afrikaans for knucklebones often used by sangomas and herbal doctors when divining. Children also used to play with these knucklebones.

The name, derived from the Afrikaans word dolos- plural dolosse, has two given derivations. Rosenthal (1961) states it to be a contraction of ‘dobbel osse’, or ‘gambling’ (Afrikaans) ‘bones’ (from Latin). Boshof and Nienaber state it to be a contraction of ‘dollen os’, or ‘play’ (old Dutch) ‘oxen’ (Afrikaans). The first is a meaning-shifted reference to ox knuckle-joint bones used in divination practices by sangomas, Southern African traditional healers. They somewhat resemble these bones. The second is a reference to ox or lamb knuckle bones used by African children at play.

Dolosse are in use across the world, either in their original shape or in variations but following similar principals. They can be found reinforcing the breakwaters of ports and harbours in the US, in South America, in Asia and in parts of Europe. There’s even one of many thousand at Port Ngqura festooned in the colours of the South African flag.

On 19 July 2016, two days before his 81st birthday, Aubrey Kruger died, being survived by his wife (Daphne Margaret Bright), his children, Gary, Sandra, Ross and Lance, and six grandchildren and five great-grandchildren.

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