Breaking swash is responsible for what action on the beach?

The breaking swash is the movement of water that occurs when waves crash onto the shore, creating a rush of water that moves up the beach. This process plays a crucial role in the transport of materials such as sand and gravel. As the breaking swash reaches the shore, it can carry sand and gravel landward. This action contributes to the formation of coastal features and beach profiles. The landward movement of sediment helps to shape the beach environment, facilitating the development and maintenance of dunes and providing habitats for various organisms.

In contrast, the other answer choices do not accurately reflect the primary function of breaking swash. While swash does result in the return flow of water to the ocean after it has moved landward, its principal role is sediment transport. The swash does not create large waves; those are the result of wind and other factors prior to breaking. Similarly, while swash can have a role in mitigating erosion by depositing sediments, it is not primarily associated with preventing coastal erosion in the way that structures or specific protective measures might. Therefore, the choice of moving sand and gravel landward accurately encapsulates the action of breaking swash on a beach.