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What are Tetrapods ?

written by: Raunekk • edited by: Lamar Stonecypher • updated: 7/23/2009

Ever been to a city's coast line and seen hundreds of identical oddly-shaped, interlocking concrete structures heaped one atop the other? If you have seen these and wondered what are and why they are there, please read on.

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    What are Tetrapods?

    If you have ever been to a coastal city and have wondered looking at the weird shaped, identical rock-like structures spread along the entire coastline, then you are reading the right article. These mysterious looking objects that you see on the shore are not rocks dumped by aliens from some other planet, but human made concrete structures known as "tetrapods".

    Tetrapod, in Greek means "four legged." If you observe a tetrapod you will see four legs protruding from a middle structure just like a star fish. These four-legged tetrapods are nothing but concrete made structures used to prevent coastal erosion. The name has become so famous that now even the three-legged concrete structures are also known as tetrapods.


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    How do they work?

    The tetrapods are designed in such a way that they dissipate the force of incoming waves by making the water flow around rather than against them. They also reduce displacement by allowing the random distribution of tetrapods to mutually interlock. Due to their weight and design, tetrapods can remain stable even under the most extreme weather conditions. A number of tetrapods arranged together form an interlocking, porous barrier that dissipates the power of waves and currents.


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    Prolonged effects on Tetrapods

    No structural design or concrete structures used in breakwaters can last forever. Even tetrapods or any other form of concrete blocks, tend to become dislodged over a period of time due to the forces of nature constantly crashing against them. Thus all the concrete structures are replaced after some point of time. Tetrapods are generally monitored through satellite photography for any kind of displacement or change in structural form.

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    Criticism of Tetrapods

    Though tetrapods are helpful structures, they have also faced a lot of criticism mainly because of their shape. Many people argue that they pose a danger to swimmers, surfers, and boaters, while others say that tetrapods in fact accelerate beach erosion by disturbing the natural processes that shape the coastal environment. Tetrapods have also been criticized for spoiling the natural coastal scenery. It is also been said that the wave action on tetrapods pulls the sand away from the shore faster than what happens in the natural process.

    Thus, even though tetrapods are widely criticized, the fact remains that they cannot be neglected. The main feature of a tetrapod lies in its design, which is not found in nature. Tetrapods are a symbol of artificiality and not aesthetics, and in spite of all the criticism have been extremely helpful in numerous ways.


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