By Enrique Álvarez del Río
Groins, also known as spurs, are structures placed transversely to the coast, which have historically been used to protect and recover beaches. In the case of Yucatan´s northern coast, they have been used for decades and to this day, they still are subject of big discussions. Do they work or do they not work? Are they beneficial to beaches or harmful? Should they be built in or should they be removed? Should they be promoted or forbidden? There are numerous cases of both success and failure.
How does the sand that forms a beach move? The sand that forms beaches, enters and leaves permanently depending on the tide and waves, but at the same time it moves parallel to the coast. That is, the grains of sand are not entering and leaving at the same point, but are moving along the beaches connected to each other. We have all seen and felt, when we swim in the sea, that the waves move us more when they are broken, than when we swim before they break. The same happens with the sand: Once the wave breaks, the sediments are suspended, and they enter and exit in a zigzag way parallel to the beach. In Yucatan, for example, most of the year, the sand moves from East to West. This is because most of the year, the waves come from the Northeast.
The source of the problem:
There is no doubt that the best way to protect a beach is by placing absolutely nothing. If the beaches are made up of sand in natural movement that maintain a beach system in equilibrium moving the sand from one beach to another, it is evident that any work that alters this natural movement and retains the sand will favor a specific beach with the logical and natural response that another stretch of beach, in which the retained sand is supposed to reach, will be affected.
This apparent solution of removing everything, absolutely everything that retains the sand movement and return to the natural state before any human intervention is not that simple. It would be necessary to begin by removing fishing refuges, ports and navigation channels in great extensions of land, which are necessary for the development of a society. In the case of Yucatan, we would have to remove everything, along almost 300 km of coast. This is obviously quite absurd.
This leads to the need to carry out both coastal protection and beach recovery works. Living with coastal interventions and understanding them in depth becomes a commitment of all. However, these must be done in such a way that they recover the sand natural movement from one beach to another, in the most possible similar way to nature. Not having in mind this priority in any decision to build coastal structures, almost always leads the solution to fail. In beaches, as in the environment in general, repairing the damages is very complex.
The obligatory question in every case: Does the groin is necessary?
The great controversy that generates the groins placement or removal, compels to answer this and other questions in the right way. Building in a groin is really needed? Would it not be a better option try to identify the root of the problem and remove those that are possible to recover the sand movement and avoid more works? If it is concluded that they should be placed, where? How long?, How high?, How much separation between them? This is about making good decisions in beach recovery. Let us jointly address this issue in future interventions.
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