Which structure is built at right angles to the beach to control erosion?

The structure that is built at right angles to the beach to control erosion is groynes. Groynes are constructed typically out of wood, stone, or concrete, and they extend from the beach into the sea. Their primary purpose is to interrupt the flow of sediment along the coast, which can help to reduce sediment loss from a beach and promote beach accretion. By trapping sand moving within the littoral drift, groynes can help to maintain and even widen beaches, thereby reducing the impact of wave action on coastal erosion.

Understanding the function of groynes is essential, as they can effectively mitigate erosion while also having secondary effects on adjacent areas of the beach, sometimes leading to variations in sediment distribution. Other structures, while aimed at coastal protection, operate differently; for example, jetties are used to protect navigation channels, breakwaters provide sheltered waters, and sea walls act as barriers against wave action but do not extend perpendicular to the beach like groynes do.