Dolosse (singular dolos) are one of the most consequential engineering inventions of the 20th century. They were born, not in a prestigious European institute or in an American military research lab, but instead of South African engineering prowess.

A dolos is a large concrete block used in coastal engineering to protect shorelines and harbour structures from strong wave action. It has a distinctive twisted geometric shape that allows it to interlock with others in a way that breaks up and dissipates the energy of incoming waves rather than resisting them directly.

But what is the history of this invention and what is its significance?

A Storm That Changed Coastal Engineering

In 1963 a powerful storm that struck the Eastern Cape, heavily damaging the East London harbour dock, led to the idea of the dolos. Before the dolos existed, the standard approach to protecting coastal infrastructure was to use large, quarried rocks and solid concrete blocks, stacked, in order to absorb punishment from powerful waves. But a solid structure takes the full fury of a wave on one surface, concentrating energy rather than dispersing it — and given enough force, even the heaviest blocks shift.

The first dolosse were deployed a year later in 1964 in East London.

The Genius of the Shape

When dolosse are piled at the water's edge, they do not form a solid wall — they interlock through their irregular geometry, creating a three-dimensional lattice full of gaps. Waves crash into this structure and find no single flat surface to push against. The water moves inward, losing force at every wave, decreasing energy by slowing it down rather than transferring it as force.

Because the dolosse are not bolted down, they can shift slightly under extreme stress, redistributing load across the whole structure rather than concentrating it at a single point.

The port of Ngqura in the Eastern Cape, about 20km from Gqeberha, holds a world record for the number of dolosse, at more than 24 000, which equates to an estimated 826 800 tonnes of concrete.

A Contested Legacy

Who deserves the credit for the design of the dolos has never been entirely settled. Eric Merrifield, the chief harbour engineer at the Port of East London, received the most recognition, winning the 1972 South African design prize.

However, the shape itself is now more widely attributed to Aubrey Kruger, a young draughtsman at the port, who produced the H-shaped structure. Neither man ever patented the invention, and so the dolos entered the public domain and spread across the world freely.

From East London to the World

The first dolosse were deployed in 1964, and by the 1970s they were appearing across Asia, Europe, North America, and South America. Today, as coastal communities and infrastructure face growing exposure to rising sea levels and more aggressive tides, dolosse are more relevant than ever.

The dolos was eventually honoured on a minted silver coin — one of which was placed in Aubrey Kruger's hands shortly before his death, a quiet recognition of his invention.

Not bad for something invented in East London, and never once patented.