dolos is a concrete block in a complex geometric shape weighing up to 20 tons, used in great numbers to protect harbour walls from the erosive force of ocean waves. Richards Bay has many of them and they play a big role in the variety of surf spots that Alkantstrand has to offer and providing shelter from the wind in different directions. During the 2015 SA Surfing Champs, local surfing legend Ray Harris handed me a few loose pages photocopied from a book telling the story of the Dolos. I don't know the origin of the book so apologies if the writer finds this article... I will gladly credit you.

Alkantstrand April Fool Joke

"King Canute couldn't hold back the ocean but Eric Merriefield of East London went a long way towards doing just that.

When gales lash the coastline and threaten harbour entrances throughout the world, breakwaters, so aptly named, help to protect them. However, breakwaters are often badly damaged, if not demolished by raging swells. Eric Mowbray Merrifield, Civil Engineer, appointed Systems harbour Engineer in East London in 1961, was well aware of the problem. The East London breakwater guarding the harbour entrance had suffered damage through many a gale. Merrifield had an idea which he hoped might remedy this.

Merrifield's father was a mechanical engineer in what was Southern Rhodesia when Eric was born in 1914. The family moved south to the gold mines in 1917 and it was at the University of the Witwatersrand that Eric gained his B.Sc. in Civil Engineering.

He started his work with the South African Railway earning the princely sum of £247 a year. From Upington, he moved to Windhoek and then to Cape Town before he took up his post in East London.

The germ of his big idea came from an incident that occurred in Table Bay, Cape Town. A small boat carrying a load of Admiralty anchors sank in harbour and the anchors interlocked into what looked like a massive chunk of iron. The only way to raise them was to send down a diver to cut them up. It was this that set Eric thinking. Sailing ships used such anchors, shaped with flukes set at 90˚ to the shaft. Could a similar shape be made to protect a harbour wall?

Once in East London, Eric thought more about it. If a shape like an H, but with one "leg" turned through 90˚, could be constructed, how would that be? It would be like a twisted anchor. If a solid mass of such shapes was put along the breakwater, surely that would rebuff the force of the ocean?

Merrifield spoke to the port draughtsman, Aubrey Kruger, about his idea. This talented man cut three pieces of broomstick and stuck them together.
"Like this?" he asked.
"Exactly." replied Merrifield.

Eric Merrifield approached a carpenter with a sketch of Kruger's design and asked if he could make a model of it. The carpenter did so but then he asked, "nou wat gaan Meneer met hierdie dolos maak?" (Now what does Master want to do with this knuckle joint). Sangomas throwing the bones used similarly shaped knuckle joint of a domestic animal. This was called a 'dolos' in Afrikaans.

The answer became clear when people in Stellenbosch evaluated Merrifield's design and it was adopted.

Originally, the dolosse (note the plural) were cast in concrete in three, four, six, seven and seventeen-ton sizes. They were declared the best form of armour ever devised for harbour protection. They have been adapted and used all over the world. And the strange name stuck.

In 1972, Eric Merrifield was present with an award for his invention by Dr Loubser, then General Manager of South African Railways and Harbours. Modern dolosse are usually made in twenty-ton sizes. One of these needs the equivalent of one and a half loads of concrete, the amount that a lorry mounted cement mixer can hold and take twenty-eight days to cure and dry. Dolosse are cast in moulds as near as possible to where it will be used since railway trucks, a crane and tractor are all needed to position the heavy shapes.

To ensure that the planners get them into the right position, a photographer dangles from the end of the boom of a crane over a drop of some twenty meters to shoot photographs. Taken at twenty-five-meter intervals, these pictures give the necessary information on where gaps occur in existing harbour protection. It may be a hair-raising experience but it gets results.

in 1998, the cost of on twenty-ton dolos was R27 000.00, including labour. This wonderful invention helps to keep East London harbour  open to shipping. It is of crucial concern to industry and commerce. People remember Eric Merrifield as a jovial, bearded gentleman who enjoyed amateur dramatics. He would practice his lines in quiet times in his office, using the voice of his character. He once became the Wonderful Wizard of Oz! A local private school has been named after him.

Research continues and minor changes have been made to the design over the years but the original concept remains effective. if you can't get to the harbour to see them there is a model of the dolos on display at the entrance to the East London Museum."

ends

The town of Richards Bay boasts the country's largest harbour and some of its most magnificent wetland scenery. It started out as a makeshift harbour set up by Sir Frederick Richards, a Commodore of the Cape, during the Anglo-Boer War of 1879. The town was laid-out on the shores of the lagoon in 1954 and proclaimed a town in 1969. The South African Government decided in 1965 to build a deep-sea harbour at Richards Bay with railway and a oil/gas pipeline linking the port to Johannesburg, about 180 kilometres north of Durban. Construction work began in 1972 and four years later, on 1 April 1976, the new harbour was opened.

Extensive use was made of dolosse (branching concrete blocks weighing up to 30 tons) to construct the two breakwaters (2400 meters long in total) protecting the harbour entrance. The dolos is a South African invention in which interlocking blocks of concrete are used to protect seawalls and preserve beaches. Due to it’s three-dimensional shape and the spaces between the solid concrete pods, a dolos does not resist the power of the ocean but dissipates the energy of the waves. Furthermore, as dolosse interlock loosely with one another, they jointly form an interconnected superstructure that rocks and rolls with the sea.

Do you have any dolosse stories? Let us know in the discussion below...