FOR many,the idea of ​​spending a pleasant holiday by the sea is extremely tempting. It can be a lot of fun: swimming, sunbathing, playing and spending time with friends and loved ones outside, with the calming sound of the waves in the background. Especially in summer, the beach has a strong charm.

All over the world, beaches stretch for thousands of miles of coastline bordering seas and lakes. They are natural leisure spaces considered immutable, sustainable, almost permanent. But for the cautious folks who visit the same beach year after year, the definitive changes are obvious. The amount of sand on the beach may vary. In some cases, drastic changes for better or for worse can be felt.

As we appreciate the attractions of the beach and observe its gradual changes, some questions may arise. Where does all the sand come from? Why do some beaches disappear, others practically disappear? Why do some beautiful areas have almost no sand in the winter, only to collect supplies during the summer months? The answers to these questions may surprise us, especially if we, like most people, tend to take beaches for granted.

Not the same

If the person has not traveled much and visited other parts of the world, it is easy to conclude that all the beaches are almost the same.But,In fact, the variations are wide: in the color, in the quality of the sand, in the slope of the beach, etc. For example, in volcanic areas, the beach is usually thick black sand derived from lava. In other areas, the sands may be more colorful as they are made up of finely ground bottom corals. Other beaches can be sparkling white, made of broken shells that turn to dust.

However, most of the beaches have sand made up of small rounded quartz crystals as well as fine particles of many different rocks. This sand comes mainly from the interior, having been brought to the sea by rivers and streams. It can range from very thick to very thin.

Indeed, it is this roughness or smoothness of the sand that largely determines the properties of the beach. If the sand on a beach is rather rough, the slope of the beach is relatively steep. These coarse grains of sand are not very compact in nature.

On the other hand, the fine sand forms a completely different type of beach. The slope of the beach will be more gradual, the water on the coast will remain shallow for longer distances, so the waves will also break more. And the fine sand is compressed very firmly, so that the cars can be driven safely. An important example is Daytona Beach, Florida, United States.

Controlled by laws

But where does all the sand come from anyway? Didn't you get the impression that this was the result of waves constantly crashing on the pebbles? It can be involved, but it's only a small percentage of the total beach sand. For most of the world's beaches, the answer is completely different. It is only in the last twenty years that people have begun to understand better the forces acting on beaches and the consequences that flow from them.

Because common weather processes differ from rock formations, the hinterlands, streams and rivers generally have varying amounts of sediment deposited at the mouth of the river. The finer sediments and clays are soon transported to the sea, leaving large amounts of sand in the riverine areas. But how this sand where the beaches are formed? To understand this transfer we need to look at some of the forces at work on the beach.

This river can flow upstream or downstream, depending on the direction of the incoming waves. This "river" on the coast is similar to its cousins ​​in the country because they can carry large amounts of sediment. The sediment carried by the "river" of the coast is, of course, the sand that forms the shore through which it flows.

The sand carried by these coastal rivers can contain large amounts; in some areas, millions of tons of sand per year. This would be equivalent to many sand wagons moving along the coast every day of the year. However, the amount varies from region to region, but it is easy to see how the sand that rivers and streams lead to the sea is distributed along the coast.

Although this process of sand transport continues continuously, another process is underway. This process changes the look of the beach from season to season. In most of the world, the incoming waves are smaller and softer during the summer months, larger and stronger during the winter. Softer waves tend to push the sand on the beach, while stormy winter waves wash the sand from the beach and place it on long hills parallel to the beach. We call these high sandbanks. When the milder waves in summer return, the sand bars tend to disappear when the sand is pushed onto the beach.

If all the sand that returned to the sea of ​​rivers remained on the shores, we would eventually have large sandy beaches throughout our continent. But it turns out that large amounts of sand are lost on the beach every year, beyond the point where waves can affect it.

The man upsets balance

The human hand, especially during the 20th century, affected the natural balance in many places. The construction of ports and breakwaters often brought about major changes in the nearby beaches. Among other effects, we can notice the accumulation of sand on one side of the harbor, the costly dredging in the harbor and the erosion on the beach on the other side. Of course, this is just one of the costs of progress from a human point of view, but there is another problem that will have deeper complications.

Flood control, water protection and hydropower plants have led to more and more dams being built in all parts of the world. These dams significantly reduce sediment transport capacity for rivers and streams, drastically reducing the supply of sand for beach construction. When the river deltas no longer provide enough sand, the beaches directly downstream begin to erode. The fine balance between gain and loss of sand was damaged.

Taking in sand from other areas and dumping it on a poor beach can only be a temporary measure, as the erosion process will continue to transport sand into the sea and the cost of replacing artificial sand may become prohibitive.

Another method of beach maintenance involves the construction of coastal structures, usually of the long and narrow type, built at angles to the shoreline and projecting into the waves. These "English", as they are called, can consist of large stones or wood. The idea is to catch the sand as you pass through the beach to avoid further erosion.

In fact, beach erosion is a growing problem, especially in densely populated areas of the world. Coastal properties in millions of dollars are in serious danger of extinction. With their very limited vision of the future, short-lived people have implemented plans to provide immediate benefits, financial or not, plans that explode on them with unexpected catastrophic results. Therefore, as large sections of the population finally get overtime for recreation, more and more natural recreation areas along the planet's coast are disappearing.

The waves generated by the sea wind end up lacking energy on the coast. But they don't always reach the shore, that is, the waves are not always parallel to the shore. For this reason, the energy of the incoming waves is divided into two parts. Most of them run perpendicular to the shore and disappear in the breaking waves. The second part, much less in total energy, is directed in a current parallel to the shore and limited between the mainland and the rum line. This current can be compared to a real river which has one "edge" on the edge of the dry shore, the other "edge" is the high seas line along which the wave begins to break.