What are groins built to achieve along shorelines?

Groins are specifically constructed along shorelines to prevent beach erosion. They are elongated structures that extend from the shore into the water, and their primary purpose is to disrupt the natural flow of sediment caused by wave action and longshore drift. By doing this, groins can help retain sand on the beach side, which contributes to building and maintaining the beach over time.

As sand accumulates on one side of the groin due to the changes in water currents, it effectively helps to widen and protect the beach area from further erosion caused by waves. This is particularly important in coastal regions where erosion can significantly impact land use, infrastructure, and ecosystems. While the other choices might relate to coastal management or development in different ways, they do not address the specific role of groins in managing beach erosion.