Longshore drift is a current that moves parallel to the shore and can cause erosion and sand shortages. It begins when waves hit the beach and carries sand downstream. Building walls or breakwaters can combat erosion, but it can also disrupt the natural ebb and flow of the beach.
Longshore drift is a natural process that describes a current that often moves mostly parallel to the shoreline of a beach. While this type of phenomenon has always happened, it is largely considered a nuisance due to the way it can change the beach in certain areas. Many refer to this drift as erosion because it moves sediment along the beach and can cause sand shortages in some areas. Some strategies have been used successfully to stop the effects of drift along coasts, but some believe these attempts have ultimately been detrimental to the environment.
The process of a longshore drift begins when waves hit the beach. Typically, the waves do not hit the shore directly, but at an angle. When the surf comes out, it takes some sand with it. The current, which goes in the same direction as the waves, carries some of that suspended sand downstream until another wave picks it up and carries it back to the beach. The current rarely changes due to the prevailing winds, and so the sand typically never returns to its original position.
The main problem with longshore dinghy sailing involves removing sand from one place and depositing it in another. While these things help shape the beach’s distinct and natural shoreline, it can be inconvenient for some property owners. Those with the most to lose are the resort owners, who depend on people coming to enjoy a good beach. If drift requires too much sand, it can actually eat away at permanent land, causing a more severe form of erosion that could eventually threaten structures.
To combat erosion, one of the most common practices is to build a wall that extends from the shoreline into the ocean at a 90 degree angle to the shoreline. This helps break the current and prevents drift from occurring. Some locations may use breakwaters built offshore to stop waves, but this technique also breaks up waves before they reach shore, which may be desirable in some locations.
The use of physical barriers to stop drift along coasts has also caused controversy. Some groups believe that the practice does not allow for the natural ebb and flow of the beach. Also, once an upstream person builds a dock to hold sand, he forces others down the line to take the same action, or the sand will be taken from them but never replaced by more upstream sand. This often leads to a long string of piers along the coast.
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