Final answer:
A groin is a low artificial structure built perpendicular to the shore to trap sand and help widen beaches by disrupting longshore drift. While it can protect beachfront property from erosion, it may cause environmental harm and increased erosion downstream.
Step-by-step explanation:
The structure described in the question is known as a groin, which is a man-made barrier extending from a beach into the ocean, designed to disrupt longshore drift. Longshore drift is a process of coastal sediment transport along the shore, which can lead to beach erosion.
Groins are built to trap sand carried by the longshore current to maintain or widen beaches, which can be crucial in protecting beachfront property from erosion. These structures are often made of wood, rock, or concrete and located in the nearshore area, which extends from the low-tide line and includes the foreshore region, continuously influenced by the waves. However, while a groin can be effective in sand accumulation on its upstream side, it may lead to increased erosion on the downstream side because it disrupts the natural sediment flow.
It is important to note that such coastal interventions can have a variety of environmental impacts. Dredging, which is often used in conjunction with groins to nourish beaches, can cause great harm to marine ecosystems including the destruction of reefs and sea grass beds, as well as causing a decline in marine life. These actions have economic as well as environmental repercussions, affecting local fisheries and tourism. Hence, while groins can be useful in the short term, they must be carefully considered within a broader coastal management plan.