#When will breakwaters come out series#

Jetties are like longer groins, often built to protect the mouths of harbors to prevent them from filling with sand. Longshore transport would move from the bottom of the picture towards the top (, Public Domain, CC0). Longshore transport would be moving from right to left, accumulating sand on the right of the groin (Beatrice Murch,, CC BY-SA 2.0).

#When will breakwaters come out series#

Eventually a beach may become covered in a series of groins, called a groin field, all trying to stabilize the natural flow of sand (Figure 13.5.1 right).įigure 13.5.1 Left: A groin on Bolinas Beach, California. To prevent that erosion, another groin must be built downstream of the first one, which then creates its own erosion problems, leading to another groin, and so on. But downstream of the groin the source of replacement sand is cut off, while sand continues to be removed, so erosion can become even more pronounced on that side of the groin. Groins are built to interrupt longshore transport and trap sand upstream of the groin, which they do very well. Groins (or groynes) are barriers built perpendicular to the shore (Figure 13.5.1 left). While some of these efforts have been successful, many others have actually exacerbated the problem, as we will see below. So from our perspective, we often see the transient nature of the coast as a threat to our activities, and as a result we have developed a number of ways to try and influence the erosion process, usually through hard stabilization, or the building of structures to stop the flow of sand.

However, we have also come to enjoy and rely on many of these beaches and other coastal features for commerce, recreation, and living space. The continued erosion and deposition of coastal sediments is a natural process, with features forming and disappearing as sea level and other conditions change.